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-rw-r--r--fs/namei.c4552
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diff --git a/fs/namei.c b/fs/namei.c
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--- /dev/null
+++ b/fs/namei.c
@@ -0,0 +1,4552 @@
+/*
+ * linux/fs/namei.c
+ *
+ * Copyright (C) 1991, 1992 Linus Torvalds
+ */
+
+/*
+ * Some corrections by tytso.
+ */
+
+/* [Feb 1997 T. Schoebel-Theuer] Complete rewrite of the pathname
+ * lookup logic.
+ */
+/* [Feb-Apr 2000, AV] Rewrite to the new namespace architecture.
+ */
+
+#include <linux/init.h>
+#include <linux/export.h>
+#include <linux/kernel.h>
+#include <linux/slab.h>
+#include <linux/fs.h>
+#include <linux/namei.h>
+#include <linux/pagemap.h>
+#include <linux/fsnotify.h>
+#include <linux/personality.h>
+#include <linux/security.h>
+#include <linux/ima.h>
+#include <linux/syscalls.h>
+#include <linux/mount.h>
+#include <linux/audit.h>
+#include <linux/capability.h>
+#include <linux/file.h>
+#include <linux/fcntl.h>
+#include <linux/device_cgroup.h>
+#include <linux/fs_struct.h>
+#include <linux/posix_acl.h>
+#include <linux/hash.h>
+#include <asm/uaccess.h>
+
+#include "internal.h"
+#include "mount.h"
+
+/* [Feb-1997 T. Schoebel-Theuer]
+ * Fundamental changes in the pathname lookup mechanisms (namei)
+ * were necessary because of omirr. The reason is that omirr needs
+ * to know the _real_ pathname, not the user-supplied one, in case
+ * of symlinks (and also when transname replacements occur).
+ *
+ * The new code replaces the old recursive symlink resolution with
+ * an iterative one (in case of non-nested symlink chains). It does
+ * this with calls to <fs>_follow_link().
+ * As a side effect, dir_namei(), _namei() and follow_link() are now
+ * replaced with a single function lookup_dentry() that can handle all
+ * the special cases of the former code.
+ *
+ * With the new dcache, the pathname is stored at each inode, at least as
+ * long as the refcount of the inode is positive. As a side effect, the
+ * size of the dcache depends on the inode cache and thus is dynamic.
+ *
+ * [29-Apr-1998 C. Scott Ananian] Updated above description of symlink
+ * resolution to correspond with current state of the code.
+ *
+ * Note that the symlink resolution is not *completely* iterative.
+ * There is still a significant amount of tail- and mid- recursion in
+ * the algorithm. Also, note that <fs>_readlink() is not used in
+ * lookup_dentry(): lookup_dentry() on the result of <fs>_readlink()
+ * may return different results than <fs>_follow_link(). Many virtual
+ * filesystems (including /proc) exhibit this behavior.
+ */
+
+/* [24-Feb-97 T. Schoebel-Theuer] Side effects caused by new implementation:
+ * New symlink semantics: when open() is called with flags O_CREAT | O_EXCL
+ * and the name already exists in form of a symlink, try to create the new
+ * name indicated by the symlink. The old code always complained that the
+ * name already exists, due to not following the symlink even if its target
+ * is nonexistent. The new semantics affects also mknod() and link() when
+ * the name is a symlink pointing to a non-existent name.
+ *
+ * I don't know which semantics is the right one, since I have no access
+ * to standards. But I found by trial that HP-UX 9.0 has the full "new"
+ * semantics implemented, while SunOS 4.1.1 and Solaris (SunOS 5.4) have the
+ * "old" one. Personally, I think the new semantics is much more logical.
+ * Note that "ln old new" where "new" is a symlink pointing to a non-existing
+ * file does succeed in both HP-UX and SunOs, but not in Solaris
+ * and in the old Linux semantics.
+ */
+
+/* [16-Dec-97 Kevin Buhr] For security reasons, we change some symlink
+ * semantics. See the comments in "open_namei" and "do_link" below.
+ *
+ * [10-Sep-98 Alan Modra] Another symlink change.
+ */
+
+/* [Feb-Apr 2000 AV] Complete rewrite. Rules for symlinks:
+ * inside the path - always follow.
+ * in the last component in creation/removal/renaming - never follow.
+ * if LOOKUP_FOLLOW passed - follow.
+ * if the pathname has trailing slashes - follow.
+ * otherwise - don't follow.
+ * (applied in that order).
+ *
+ * [Jun 2000 AV] Inconsistent behaviour of open() in case if flags==O_CREAT
+ * restored for 2.4. This is the last surviving part of old 4.2BSD bug.
+ * During the 2.4 we need to fix the userland stuff depending on it -
+ * hopefully we will be able to get rid of that wart in 2.5. So far only
+ * XEmacs seems to be relying on it...
+ */
+/*
+ * [Sep 2001 AV] Single-semaphore locking scheme (kudos to David Holland)
+ * implemented. Let's see if raised priority of ->s_vfs_rename_mutex gives
+ * any extra contention...
+ */
+
+/* In order to reduce some races, while at the same time doing additional
+ * checking and hopefully speeding things up, we copy filenames to the
+ * kernel data space before using them..
+ *
+ * POSIX.1 2.4: an empty pathname is invalid (ENOENT).
+ * PATH_MAX includes the nul terminator --RR.
+ */
+
+#define EMBEDDED_NAME_MAX (PATH_MAX - offsetof(struct filename, iname))
+
+struct filename *
+getname_flags(const char __user *filename, int flags, int *empty)
+{
+ struct filename *result;
+ char *kname;
+ int len;
+
+ result = audit_reusename(filename);
+ if (result)
+ return result;
+
+ result = __getname();
+ if (unlikely(!result))
+ return ERR_PTR(-ENOMEM);
+
+ /*
+ * First, try to embed the struct filename inside the names_cache
+ * allocation
+ */
+ kname = (char *)result->iname;
+ result->name = kname;
+
+ len = strncpy_from_user(kname, filename, EMBEDDED_NAME_MAX);
+ if (unlikely(len < 0)) {
+ __putname(result);
+ return ERR_PTR(len);
+ }
+
+ /*
+ * Uh-oh. We have a name that's approaching PATH_MAX. Allocate a
+ * separate struct filename so we can dedicate the entire
+ * names_cache allocation for the pathname, and re-do the copy from
+ * userland.
+ */
+ if (unlikely(len == EMBEDDED_NAME_MAX)) {
+ const size_t size = offsetof(struct filename, iname[1]);
+ kname = (char *)result;
+
+ /*
+ * size is chosen that way we to guarantee that
+ * result->iname[0] is within the same object and that
+ * kname can't be equal to result->iname, no matter what.
+ */
+ result = kzalloc(size, GFP_KERNEL);
+ if (unlikely(!result)) {
+ __putname(kname);
+ return ERR_PTR(-ENOMEM);
+ }
+ result->name = kname;
+ len = strncpy_from_user(kname, filename, PATH_MAX);
+ if (unlikely(len < 0)) {
+ __putname(kname);
+ kfree(result);
+ return ERR_PTR(len);
+ }
+ if (unlikely(len == PATH_MAX)) {
+ __putname(kname);
+ kfree(result);
+ return ERR_PTR(-ENAMETOOLONG);
+ }
+ }
+
+ result->refcnt = 1;
+ /* The empty path is special. */
+ if (unlikely(!len)) {
+ if (empty)
+ *empty = 1;
+ if (!(flags & LOOKUP_EMPTY)) {
+ putname(result);
+ return ERR_PTR(-ENOENT);
+ }
+ }
+
+ result->uptr = filename;
+ result->aname = NULL;
+ audit_getname(result);
+ return result;
+}
+
+struct filename *
+getname(const char __user * filename)
+{
+ return getname_flags(filename, 0, NULL);
+}
+
+struct filename *
+getname_kernel(const char * filename)
+{
+ struct filename *result;
+ int len = strlen(filename) + 1;
+
+ result = __getname();
+ if (unlikely(!result))
+ return ERR_PTR(-ENOMEM);
+
+ if (len <= EMBEDDED_NAME_MAX) {
+ result->name = (char *)result->iname;
+ } else if (len <= PATH_MAX) {
+ struct filename *tmp;
+
+ tmp = kmalloc(sizeof(*tmp), GFP_KERNEL);
+ if (unlikely(!tmp)) {
+ __putname(result);
+ return ERR_PTR(-ENOMEM);
+ }
+ tmp->name = (char *)result;
+ result = tmp;
+ } else {
+ __putname(result);
+ return ERR_PTR(-ENAMETOOLONG);
+ }
+ memcpy((char *)result->name, filename, len);
+ result->uptr = NULL;
+ result->aname = NULL;
+ result->refcnt = 1;
+ audit_getname(result);
+
+ return result;
+}
+
+void putname(struct filename *name)
+{
+ BUG_ON(name->refcnt <= 0);
+
+ if (--name->refcnt > 0)
+ return;
+
+ if (name->name != name->iname) {
+ __putname(name->name);
+ kfree(name);
+ } else
+ __putname(name);
+}
+
+static int check_acl(struct inode *inode, int mask)
+{
+#ifdef CONFIG_FS_POSIX_ACL
+ struct posix_acl *acl;
+
+ if (mask & MAY_NOT_BLOCK) {
+ acl = get_cached_acl_rcu(inode, ACL_TYPE_ACCESS);
+ if (!acl)
+ return -EAGAIN;
+ /* no ->get_acl() calls in RCU mode... */
+ if (acl == ACL_NOT_CACHED)
+ return -ECHILD;
+ return posix_acl_permission(inode, acl, mask & ~MAY_NOT_BLOCK);
+ }
+
+ acl = get_acl(inode, ACL_TYPE_ACCESS);
+ if (IS_ERR(acl))
+ return PTR_ERR(acl);
+ if (acl) {
+ int error = posix_acl_permission(inode, acl, mask);
+ posix_acl_release(acl);
+ return error;
+ }
+#endif
+
+ return -EAGAIN;
+}
+
+/*
+ * This does the basic permission checking
+ */
+static int acl_permission_check(struct inode *inode, int mask)
+{
+ unsigned int mode = inode->i_mode;
+
+ if (likely(uid_eq(current_fsuid(), inode->i_uid)))
+ mode >>= 6;
+ else {
+ if (IS_POSIXACL(inode) && (mode & S_IRWXG)) {
+ int error = check_acl(inode, mask);
+ if (error != -EAGAIN)
+ return error;
+ }
+
+ if (in_group_p(inode->i_gid))
+ mode >>= 3;
+ }
+
+ /*
+ * If the DACs are ok we don't need any capability check.
+ */
+ if ((mask & ~mode & (MAY_READ | MAY_WRITE | MAY_EXEC)) == 0)
+ return 0;
+ return -EACCES;
+}
+
+/**
+ * generic_permission - check for access rights on a Posix-like filesystem
+ * @inode: inode to check access rights for
+ * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC, ...)
+ *
+ * Used to check for read/write/execute permissions on a file.
+ * We use "fsuid" for this, letting us set arbitrary permissions
+ * for filesystem access without changing the "normal" uids which
+ * are used for other things.
+ *
+ * generic_permission is rcu-walk aware. It returns -ECHILD in case an rcu-walk
+ * request cannot be satisfied (eg. requires blocking or too much complexity).
+ * It would then be called again in ref-walk mode.
+ */
+int generic_permission(struct inode *inode, int mask)
+{
+ int ret;
+
+ /*
+ * Do the basic permission checks.
+ */
+ ret = acl_permission_check(inode, mask);
+ if (ret != -EACCES)
+ return ret;
+
+ if (S_ISDIR(inode->i_mode)) {
+ /* DACs are overridable for directories */
+ if (capable_wrt_inode_uidgid(inode, CAP_DAC_OVERRIDE))
+ return 0;
+ if (!(mask & MAY_WRITE))
+ if (capable_wrt_inode_uidgid(inode,
+ CAP_DAC_READ_SEARCH))
+ return 0;
+ return -EACCES;
+ }
+ /*
+ * Read/write DACs are always overridable.
+ * Executable DACs are overridable when there is
+ * at least one exec bit set.
+ */
+ if (!(mask & MAY_EXEC) || (inode->i_mode & S_IXUGO))
+ if (capable_wrt_inode_uidgid(inode, CAP_DAC_OVERRIDE))
+ return 0;
+
+ /*
+ * Searching includes executable on directories, else just read.
+ */
+ mask &= MAY_READ | MAY_WRITE | MAY_EXEC;
+ if (mask == MAY_READ)
+ if (capable_wrt_inode_uidgid(inode, CAP_DAC_READ_SEARCH))
+ return 0;
+
+ return -EACCES;
+}
+EXPORT_SYMBOL(generic_permission);
+
+/*
+ * We _really_ want to just do "generic_permission()" without
+ * even looking at the inode->i_op values. So we keep a cache
+ * flag in inode->i_opflags, that says "this has not special
+ * permission function, use the fast case".
+ */
+static inline int do_inode_permission(struct inode *inode, int mask)
+{
+ if (unlikely(!(inode->i_opflags & IOP_FASTPERM))) {
+ if (likely(inode->i_op->permission))
+ return inode->i_op->permission(inode, mask);
+
+ /* This gets set once for the inode lifetime */
+ spin_lock(&inode->i_lock);
+ inode->i_opflags |= IOP_FASTPERM;
+ spin_unlock(&inode->i_lock);
+ }
+ return generic_permission(inode, mask);
+}
+
+/**
+ * __inode_permission - Check for access rights to a given inode
+ * @inode: Inode to check permission on
+ * @mask: Right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
+ *
+ * Check for read/write/execute permissions on an inode.
+ *
+ * When checking for MAY_APPEND, MAY_WRITE must also be set in @mask.
+ *
+ * This does not check for a read-only file system. You probably want
+ * inode_permission().
+ */
+int __inode_permission(struct inode *inode, int mask)
+{
+ int retval;
+
+ if (unlikely(mask & MAY_WRITE)) {
+ /*
+ * Nobody gets write access to an immutable file.
+ */
+ if (IS_IMMUTABLE(inode))
+ return -EACCES;
+ }
+
+ retval = do_inode_permission(inode, mask);
+ if (retval)
+ return retval;
+
+ retval = devcgroup_inode_permission(inode, mask);
+ if (retval)
+ return retval;
+
+ return security_inode_permission(inode, mask);
+}
+EXPORT_SYMBOL(__inode_permission);
+
+/**
+ * sb_permission - Check superblock-level permissions
+ * @sb: Superblock of inode to check permission on
+ * @inode: Inode to check permission on
+ * @mask: Right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
+ *
+ * Separate out file-system wide checks from inode-specific permission checks.
+ */
+static int sb_permission(struct super_block *sb, struct inode *inode, int mask)
+{
+ if (unlikely(mask & MAY_WRITE)) {
+ umode_t mode = inode->i_mode;
+
+ /* Nobody gets write access to a read-only fs. */
+ if ((sb->s_flags & MS_RDONLY) &&
+ (S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode)))
+ return -EROFS;
+ }
+ return 0;
+}
+
+/**
+ * inode_permission - Check for access rights to a given inode
+ * @inode: Inode to check permission on
+ * @mask: Right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
+ *
+ * Check for read/write/execute permissions on an inode. We use fs[ug]id for
+ * this, letting us set arbitrary permissions for filesystem access without
+ * changing the "normal" UIDs which are used for other things.
+ *
+ * When checking for MAY_APPEND, MAY_WRITE must also be set in @mask.
+ */
+int inode_permission(struct inode *inode, int mask)
+{
+ int retval;
+
+ retval = sb_permission(inode->i_sb, inode, mask);
+ if (retval)
+ return retval;
+ return __inode_permission(inode, mask);
+}
+EXPORT_SYMBOL(inode_permission);
+
+/**
+ * path_get - get a reference to a path
+ * @path: path to get the reference to
+ *
+ * Given a path increment the reference count to the dentry and the vfsmount.
+ */
+void path_get(const struct path *path)
+{
+ mntget(path->mnt);
+ dget(path->dentry);
+}
+EXPORT_SYMBOL(path_get);
+
+/**
+ * path_put - put a reference to a path
+ * @path: path to put the reference to
+ *
+ * Given a path decrement the reference count to the dentry and the vfsmount.
+ */
+void path_put(const struct path *path)
+{
+ dput(path->dentry);
+ mntput(path->mnt);
+}
+EXPORT_SYMBOL(path_put);
+
+struct nameidata {
+ struct path path;
+ struct qstr last;
+ struct path root;
+ struct inode *inode; /* path.dentry.d_inode */
+ unsigned int flags;
+ unsigned seq, m_seq;
+ int last_type;
+ unsigned depth;
+ struct file *base;
+ char *saved_names[MAX_NESTED_LINKS + 1];
+};
+
+/*
+ * Path walking has 2 modes, rcu-walk and ref-walk (see
+ * Documentation/filesystems/path-lookup.txt). In situations when we can't
+ * continue in RCU mode, we attempt to drop out of rcu-walk mode and grab
+ * normal reference counts on dentries and vfsmounts to transition to rcu-walk
+ * mode. Refcounts are grabbed at the last known good point before rcu-walk
+ * got stuck, so ref-walk may continue from there. If this is not successful
+ * (eg. a seqcount has changed), then failure is returned and it's up to caller
+ * to restart the path walk from the beginning in ref-walk mode.
+ */
+
+/**
+ * unlazy_walk - try to switch to ref-walk mode.
+ * @nd: nameidata pathwalk data
+ * @dentry: child of nd->path.dentry or NULL
+ * Returns: 0 on success, -ECHILD on failure
+ *
+ * unlazy_walk attempts to legitimize the current nd->path, nd->root and dentry
+ * for ref-walk mode. @dentry must be a path found by a do_lookup call on
+ * @nd or NULL. Must be called from rcu-walk context.
+ */
+static int unlazy_walk(struct nameidata *nd, struct dentry *dentry)
+{
+ struct fs_struct *fs = current->fs;
+ struct dentry *parent = nd->path.dentry;
+
+ BUG_ON(!(nd->flags & LOOKUP_RCU));
+
+ /*
+ * After legitimizing the bastards, terminate_walk()
+ * will do the right thing for non-RCU mode, and all our
+ * subsequent exit cases should rcu_read_unlock()
+ * before returning. Do vfsmount first; if dentry
+ * can't be legitimized, just set nd->path.dentry to NULL
+ * and rely on dput(NULL) being a no-op.
+ */
+ if (!legitimize_mnt(nd->path.mnt, nd->m_seq))
+ return -ECHILD;
+ nd->flags &= ~LOOKUP_RCU;
+
+ if (!lockref_get_not_dead(&parent->d_lockref)) {
+ nd->path.dentry = NULL;
+ goto out;
+ }
+
+ /*
+ * For a negative lookup, the lookup sequence point is the parents
+ * sequence point, and it only needs to revalidate the parent dentry.
+ *
+ * For a positive lookup, we need to move both the parent and the
+ * dentry from the RCU domain to be properly refcounted. And the
+ * sequence number in the dentry validates *both* dentry counters,
+ * since we checked the sequence number of the parent after we got
+ * the child sequence number. So we know the parent must still
+ * be valid if the child sequence number is still valid.
+ */
+ if (!dentry) {
+ if (read_seqcount_retry(&parent->d_seq, nd->seq))
+ goto out;
+ BUG_ON(nd->inode != parent->d_inode);
+ } else {
+ if (!lockref_get_not_dead(&dentry->d_lockref))
+ goto out;
+ if (read_seqcount_retry(&dentry->d_seq, nd->seq))
+ goto drop_dentry;
+ }
+
+ /*
+ * Sequence counts matched. Now make sure that the root is
+ * still valid and get it if required.
+ */
+ if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT)) {
+ spin_lock(&fs->lock);
+ if (nd->root.mnt != fs->root.mnt || nd->root.dentry != fs->root.dentry)
+ goto unlock_and_drop_dentry;
+ path_get(&nd->root);
+ spin_unlock(&fs->lock);
+ }
+
+ rcu_read_unlock();
+ return 0;
+
+unlock_and_drop_dentry:
+ spin_unlock(&fs->lock);
+drop_dentry:
+ rcu_read_unlock();
+ dput(dentry);
+ goto drop_root_mnt;
+out:
+ rcu_read_unlock();
+drop_root_mnt:
+ if (!(nd->flags & LOOKUP_ROOT))
+ nd->root.mnt = NULL;
+ return -ECHILD;
+}
+
+static inline int d_revalidate(struct dentry *dentry, unsigned int flags)
+{
+ return dentry->d_op->d_revalidate(dentry, flags);
+}
+
+/**
+ * complete_walk - successful completion of path walk
+ * @nd: pointer nameidata
+ *
+ * If we had been in RCU mode, drop out of it and legitimize nd->path.
+ * Revalidate the final result, unless we'd already done that during
+ * the path walk or the filesystem doesn't ask for it. Return 0 on
+ * success, -error on failure. In case of failure caller does not
+ * need to drop nd->path.
+ */
+static int complete_walk(struct nameidata *nd)
+{
+ struct dentry *dentry = nd->path.dentry;
+ int status;
+
+ if (nd->flags & LOOKUP_RCU) {
+ nd->flags &= ~LOOKUP_RCU;
+ if (!(nd->flags & LOOKUP_ROOT))
+ nd->root.mnt = NULL;
+
+ if (!legitimize_mnt(nd->path.mnt, nd->m_seq)) {
+ rcu_read_unlock();
+ return -ECHILD;
+ }
+ if (unlikely(!lockref_get_not_dead(&dentry->d_lockref))) {
+ rcu_read_unlock();
+ mntput(nd->path.mnt);
+ return -ECHILD;
+ }
+ if (read_seqcount_retry(&dentry->d_seq, nd->seq)) {
+ rcu_read_unlock();
+ dput(dentry);
+ mntput(nd->path.mnt);
+ return -ECHILD;
+ }
+ rcu_read_unlock();
+ }
+
+ if (likely(!(nd->flags & LOOKUP_JUMPED)))
+ return 0;
+
+ if (likely(!(dentry->d_flags & DCACHE_OP_WEAK_REVALIDATE)))
+ return 0;
+
+ status = dentry->d_op->d_weak_revalidate(dentry, nd->flags);
+ if (status > 0)
+ return 0;
+
+ if (!status)
+ status = -ESTALE;
+
+ path_put(&nd->path);
+ return status;
+}
+
+static __always_inline void set_root(struct nameidata *nd)
+{
+ get_fs_root(current->fs, &nd->root);
+}
+
+static int link_path_walk(const char *, struct nameidata *);
+
+static __always_inline unsigned set_root_rcu(struct nameidata *nd)
+{
+ struct fs_struct *fs = current->fs;
+ unsigned seq, res;
+
+ do {
+ seq = read_seqcount_begin(&fs->seq);
+ nd->root = fs->root;
+ res = __read_seqcount_begin(&nd->root.dentry->d_seq);
+ } while (read_seqcount_retry(&fs->seq, seq));
+ return res;
+}
+
+static void path_put_conditional(struct path *path, struct nameidata *nd)
+{
+ dput(path->dentry);
+ if (path->mnt != nd->path.mnt)
+ mntput(path->mnt);
+}
+
+static inline void path_to_nameidata(const struct path *path,
+ struct nameidata *nd)
+{
+ if (!(nd->flags & LOOKUP_RCU)) {
+ dput(nd->path.dentry);
+ if (nd->path.mnt != path->mnt)
+ mntput(nd->path.mnt);
+ }
+ nd->path.mnt = path->mnt;
+ nd->path.dentry = path->dentry;
+}
+
+/*
+ * Helper to directly jump to a known parsed path from ->follow_link,
+ * caller must have taken a reference to path beforehand.
+ */
+void nd_jump_link(struct nameidata *nd, struct path *path)
+{
+ path_put(&nd->path);
+
+ nd->path = *path;
+ nd->inode = nd->path.dentry->d_inode;
+ nd->flags |= LOOKUP_JUMPED;
+}
+
+void nd_set_link(struct nameidata *nd, char *path)
+{
+ nd->saved_names[nd->depth] = path;
+}
+EXPORT_SYMBOL(nd_set_link);
+
+char *nd_get_link(struct nameidata *nd)
+{
+ return nd->saved_names[nd->depth];
+}
+EXPORT_SYMBOL(nd_get_link);
+
+static inline void put_link(struct nameidata *nd, struct path *link, void *cookie)
+{
+ struct inode *inode = link->dentry->d_inode;
+ if (inode->i_op->put_link)
+ inode->i_op->put_link(link->dentry, nd, cookie);
+ path_put(link);
+}
+
+int sysctl_protected_symlinks __read_mostly = 0;
+int sysctl_protected_hardlinks __read_mostly = 0;
+
+/**
+ * may_follow_link - Check symlink following for unsafe situations
+ * @link: The path of the symlink
+ * @nd: nameidata pathwalk data
+ *
+ * In the case of the sysctl_protected_symlinks sysctl being enabled,
+ * CAP_DAC_OVERRIDE needs to be specifically ignored if the symlink is
+ * in a sticky world-writable directory. This is to protect privileged
+ * processes from failing races against path names that may change out
+ * from under them by way of other users creating malicious symlinks.
+ * It will permit symlinks to be followed only when outside a sticky
+ * world-writable directory, or when the uid of the symlink and follower
+ * match, or when the directory owner matches the symlink's owner.
+ *
+ * Returns 0 if following the symlink is allowed, -ve on error.
+ */
+static inline int may_follow_link(struct path *link, struct nameidata *nd)
+{
+ const struct inode *inode;
+ const struct inode *parent;
+
+ if (!sysctl_protected_symlinks)
+ return 0;
+
+ /* Allowed if owner and follower match. */
+ inode = link->dentry->d_inode;
+ if (uid_eq(current_cred()->fsuid, inode->i_uid))
+ return 0;
+
+ /* Allowed if parent directory not sticky and world-writable. */
+ parent = nd->path.dentry->d_inode;
+ if ((parent->i_mode & (S_ISVTX|S_IWOTH)) != (S_ISVTX|S_IWOTH))
+ return 0;
+
+ /* Allowed if parent directory and link owner match. */
+ if (uid_eq(parent->i_uid, inode->i_uid))
+ return 0;
+
+ audit_log_link_denied("follow_link", link);
+ path_put_conditional(link, nd);
+ path_put(&nd->path);
+ return -EACCES;
+}
+
+/**
+ * safe_hardlink_source - Check for safe hardlink conditions
+ * @inode: the source inode to hardlink from
+ *
+ * Return false if at least one of the following conditions:
+ * - inode is not a regular file
+ * - inode is setuid
+ * - inode is setgid and group-exec
+ * - access failure for read and write
+ *
+ * Otherwise returns true.
+ */
+static bool safe_hardlink_source(struct inode *inode)
+{
+ umode_t mode = inode->i_mode;
+
+ /* Special files should not get pinned to the filesystem. */
+ if (!S_ISREG(mode))
+ return false;
+
+ /* Setuid files should not get pinned to the filesystem. */
+ if (mode & S_ISUID)
+ return false;
+
+ /* Executable setgid files should not get pinned to the filesystem. */
+ if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP))
+ return false;
+
+ /* Hardlinking to unreadable or unwritable sources is dangerous. */
+ if (inode_permission(inode, MAY_READ | MAY_WRITE))
+ return false;
+
+ return true;
+}
+
+/**
+ * may_linkat - Check permissions for creating a hardlink
+ * @link: the source to hardlink from
+ *
+ * Block hardlink when all of:
+ * - sysctl_protected_hardlinks enabled
+ * - fsuid does not match inode
+ * - hardlink source is unsafe (see safe_hardlink_source() above)
+ * - not CAP_FOWNER
+ *
+ * Returns 0 if successful, -ve on error.
+ */
+static int may_linkat(struct path *link)
+{
+ const struct cred *cred;
+ struct inode *inode;
+
+ if (!sysctl_protected_hardlinks)
+ return 0;
+
+ cred = current_cred();
+ inode = link->dentry->d_inode;
+
+ /* Source inode owner (or CAP_FOWNER) can hardlink all they like,
+ * otherwise, it must be a safe source.
+ */
+ if (uid_eq(cred->fsuid, inode->i_uid) || safe_hardlink_source(inode) ||
+ capable(CAP_FOWNER))
+ return 0;
+
+ audit_log_link_denied("linkat", link);
+ return -EPERM;
+}
+
+static __always_inline int
+follow_link(struct path *link, struct nameidata *nd, void **p)
+{
+ struct dentry *dentry = link->dentry;
+ int error;
+ char *s;
+
+ BUG_ON(nd->flags & LOOKUP_RCU);
+
+ if (link->mnt == nd->path.mnt)
+ mntget(link->mnt);
+
+ error = -ELOOP;
+ if (unlikely(current->total_link_count >= 40))
+ goto out_put_nd_path;
+
+ cond_resched();
+ current->total_link_count++;
+
+ touch_atime(link);
+ nd_set_link(nd, NULL);
+
+ error = security_inode_follow_link(link->dentry, nd);
+ if (error)
+ goto out_put_nd_path;
+
+ nd->last_type = LAST_BIND;
+ *p = dentry->d_inode->i_op->follow_link(dentry, nd);
+ error = PTR_ERR(*p);
+ if (IS_ERR(*p))
+ goto out_put_nd_path;
+
+ error = 0;
+ s = nd_get_link(nd);
+ if (s) {
+ if (unlikely(IS_ERR(s))) {
+ path_put(&nd->path);
+ put_link(nd, link, *p);
+ return PTR_ERR(s);
+ }
+ if (*s == '/') {
+ if (!nd->root.mnt)
+ set_root(nd);
+ path_put(&nd->path);
+ nd->path = nd->root;
+ path_get(&nd->root);
+ nd->flags |= LOOKUP_JUMPED;
+ }
+ nd->inode = nd->path.dentry->d_inode;
+ error = link_path_walk(s, nd);
+ if (unlikely(error))
+ put_link(nd, link, *p);
+ }
+
+ return error;
+
+out_put_nd_path:
+ *p = NULL;
+ path_put(&nd->path);
+ path_put(link);
+ return error;
+}
+
+static int follow_up_rcu(struct path *path)
+{
+ struct mount *mnt = real_mount(path->mnt);
+ struct mount *parent;
+ struct dentry *mountpoint;
+
+ parent = mnt->mnt_parent;
+ if (&parent->mnt == path->mnt)
+ return 0;
+ mountpoint = mnt->mnt_mountpoint;
+ path->dentry = mountpoint;
+ path->mnt = &parent->mnt;
+ return 1;
+}
+
+/*
+ * follow_up - Find the mountpoint of path's vfsmount
+ *
+ * Given a path, find the mountpoint of its source file system.
+ * Replace @path with the path of the mountpoint in the parent mount.
+ * Up is towards /.
+ *
+ * Return 1 if we went up a level and 0 if we were already at the
+ * root.
+ */
+int follow_up(struct path *path)
+{
+ struct mount *mnt = real_mount(path->mnt);
+ struct mount *parent;
+ struct dentry *mountpoint;
+
+ read_seqlock_excl(&mount_lock);
+ parent = mnt->mnt_parent;
+ if (parent == mnt) {
+ read_sequnlock_excl(&mount_lock);
+ return 0;
+ }
+ mntget(&parent->mnt);
+ mountpoint = dget(mnt->mnt_mountpoint);
+ read_sequnlock_excl(&mount_lock);
+ dput(path->dentry);
+ path->dentry = mountpoint;
+ mntput(path->mnt);
+ path->mnt = &parent->mnt;
+ return 1;
+}
+EXPORT_SYMBOL(follow_up);
+
+/*
+ * Perform an automount
+ * - return -EISDIR to tell follow_managed() to stop and return the path we
+ * were called with.
+ */
+static int follow_automount(struct path *path, unsigned flags,
+ bool *need_mntput)
+{
+ struct vfsmount *mnt;
+ int err;
+
+ if (!path->dentry->d_op || !path->dentry->d_op->d_automount)
+ return -EREMOTE;
+
+ /* We don't want to mount if someone's just doing a stat -
+ * unless they're stat'ing a directory and appended a '/' to
+ * the name.
+ *
+ * We do, however, want to mount if someone wants to open or
+ * create a file of any type under the mountpoint, wants to
+ * traverse through the mountpoint or wants to open the
+ * mounted directory. Also, autofs may mark negative dentries
+ * as being automount points. These will need the attentions
+ * of the daemon to instantiate them before they can be used.
+ */
+ if (!(flags & (LOOKUP_PARENT | LOOKUP_DIRECTORY |
+ LOOKUP_OPEN | LOOKUP_CREATE | LOOKUP_AUTOMOUNT)) &&
+ path->dentry->d_inode)
+ return -EISDIR;
+
+ current->total_link_count++;
+ if (current->total_link_count >= 40)
+ return -ELOOP;
+
+ mnt = path->dentry->d_op->d_automount(path);
+ if (IS_ERR(mnt)) {
+ /*
+ * The filesystem is allowed to return -EISDIR here to indicate
+ * it doesn't want to automount. For instance, autofs would do
+ * this so that its userspace daemon can mount on this dentry.
+ *
+ * However, we can only permit this if it's a terminal point in
+ * the path being looked up; if it wasn't then the remainder of
+ * the path is inaccessible and we should say so.
+ */
+ if (PTR_ERR(mnt) == -EISDIR && (flags & LOOKUP_PARENT))
+ return -EREMOTE;
+ return PTR_ERR(mnt);
+ }
+
+ if (!mnt) /* mount collision */
+ return 0;
+
+ if (!*need_mntput) {
+ /* lock_mount() may release path->mnt on error */
+ mntget(path->mnt);
+ *need_mntput = true;
+ }
+ err = finish_automount(mnt, path);
+
+ switch (err) {
+ case -EBUSY:
+ /* Someone else made a mount here whilst we were busy */
+ return 0;
+ case 0:
+ path_put(path);
+ path->mnt = mnt;
+ path->dentry = dget(mnt->mnt_root);
+ return 0;
+ default:
+ return err;
+ }
+
+}
+
+/*
+ * Handle a dentry that is managed in some way.
+ * - Flagged for transit management (autofs)
+ * - Flagged as mountpoint
+ * - Flagged as automount point
+ *
+ * This may only be called in refwalk mode.
+ *
+ * Serialization is taken care of in namespace.c
+ */
+static int follow_managed(struct path *path, unsigned flags)
+{
+ struct vfsmount *mnt = path->mnt; /* held by caller, must be left alone */
+ unsigned managed;
+ bool need_mntput = false;
+ int ret = 0;
+
+ /* Given that we're not holding a lock here, we retain the value in a
+ * local variable for each dentry as we look at it so that we don't see
+ * the components of that value change under us */
+ while (managed = ACCESS_ONCE(path->dentry->d_flags),
+ managed &= DCACHE_MANAGED_DENTRY,
+ unlikely(managed != 0)) {
+ /* Allow the filesystem to manage the transit without i_mutex
+ * being held. */
+ if (managed & DCACHE_MANAGE_TRANSIT) {
+ BUG_ON(!path->dentry->d_op);
+ BUG_ON(!path->dentry->d_op->d_manage);
+ ret = path->dentry->d_op->d_manage(path->dentry, false);
+ if (ret < 0)
+ break;
+ }
+
+ /* Transit to a mounted filesystem. */
+ if (managed & DCACHE_MOUNTED) {
+ struct vfsmount *mounted = lookup_mnt(path);
+ if (mounted) {
+ dput(path->dentry);
+ if (need_mntput)
+ mntput(path->mnt);
+ path->mnt = mounted;
+ path->dentry = dget(mounted->mnt_root);
+ need_mntput = true;
+ continue;
+ }
+
+ /* Something is mounted on this dentry in another
+ * namespace and/or whatever was mounted there in this
+ * namespace got unmounted before lookup_mnt() could
+ * get it */
+ }
+
+ /* Handle an automount point */
+ if (managed & DCACHE_NEED_AUTOMOUNT) {
+ ret = follow_automount(path, flags, &need_mntput);
+ if (ret < 0)
+ break;
+ continue;
+ }
+
+ /* We didn't change the current path point */
+ break;
+ }
+
+ if (need_mntput && path->mnt == mnt)
+ mntput(path->mnt);
+ if (ret == -EISDIR)
+ ret = 0;
+ return ret < 0 ? ret : need_mntput;
+}
+
+int follow_down_one(struct path *path)
+{
+ struct vfsmount *mounted;
+
+ mounted = lookup_mnt(path);
+ if (mounted) {
+ dput(path->dentry);
+ mntput(path->mnt);
+ path->mnt = mounted;
+ path->dentry = dget(mounted->mnt_root);
+ return 1;
+ }
+ return 0;
+}
+EXPORT_SYMBOL(follow_down_one);
+
+static inline int managed_dentry_rcu(struct dentry *dentry)
+{
+ return (dentry->d_flags & DCACHE_MANAGE_TRANSIT) ?
+ dentry->d_op->d_manage(dentry, true) : 0;
+}
+
+/*
+ * Try to skip to top of mountpoint pile in rcuwalk mode. Fail if
+ * we meet a managed dentry that would need blocking.
+ */
+static bool __follow_mount_rcu(struct nameidata *nd, struct path *path,
+ struct inode **inode)
+{
+ for (;;) {
+ struct mount *mounted;
+ /*
+ * Don't forget we might have a non-mountpoint managed dentry
+ * that wants to block transit.
+ */
+ switch (managed_dentry_rcu(path->dentry)) {
+ case -ECHILD:
+ default:
+ return false;
+ case -EISDIR:
+ return true;
+ case 0:
+ break;
+ }
+
+ if (!d_mountpoint(path->dentry))
+ return !(path->dentry->d_flags & DCACHE_NEED_AUTOMOUNT);
+
+ mounted = __lookup_mnt(path->mnt, path->dentry);
+ if (!mounted)
+ break;
+ path->mnt = &mounted->mnt;
+ path->dentry = mounted->mnt.mnt_root;
+ nd->flags |= LOOKUP_JUMPED;
+ nd->seq = read_seqcount_begin(&path->dentry->d_seq);
+ /*
+ * Update the inode too. We don't need to re-check the
+ * dentry sequence number here after this d_inode read,
+ * because a mount-point is always pinned.
+ */
+ *inode = path->dentry->d_inode;
+ }
+ return !read_seqretry(&mount_lock, nd->m_seq) &&
+ !(path->dentry->d_flags & DCACHE_NEED_AUTOMOUNT);
+}
+
+static int follow_dotdot_rcu(struct nameidata *nd)
+{
+ struct inode *inode = nd->inode;
+ if (!nd->root.mnt)
+ set_root_rcu(nd);
+
+ while (1) {
+ if (nd->path.dentry == nd->root.dentry &&
+ nd->path.mnt == nd->root.mnt) {
+ break;
+ }
+ if (nd->path.dentry != nd->path.mnt->mnt_root) {
+ struct dentry *old = nd->path.dentry;
+ struct dentry *parent = old->d_parent;
+ unsigned seq;
+
+ inode = parent->d_inode;
+ seq = read_seqcount_begin(&parent->d_seq);
+ if (read_seqcount_retry(&old->d_seq, nd->seq))
+ goto failed;
+ nd->path.dentry = parent;
+ nd->seq = seq;
+ break;
+ }
+ if (!follow_up_rcu(&nd->path))
+ break;
+ inode = nd->path.dentry->d_inode;
+ nd->seq = read_seqcount_begin(&nd->path.dentry->d_seq);
+ }
+ while (d_mountpoint(nd->path.dentry)) {
+ struct mount *mounted;
+ mounted = __lookup_mnt(nd->path.mnt, nd->path.dentry);
+ if (!mounted)
+ break;
+ nd->path.mnt = &mounted->mnt;
+ nd->path.dentry = mounted->mnt.mnt_root;
+ inode = nd->path.dentry->d_inode;
+ nd->seq = read_seqcount_begin(&nd->path.dentry->d_seq);
+ if (read_seqretry(&mount_lock, nd->m_seq))
+ goto failed;
+ }
+ nd->inode = inode;
+ return 0;
+
+failed:
+ nd->flags &= ~LOOKUP_RCU;
+ if (!(nd->flags & LOOKUP_ROOT))
+ nd->root.mnt = NULL;
+ rcu_read_unlock();
+ return -ECHILD;
+}
+
+/*
+ * Follow down to the covering mount currently visible to userspace. At each
+ * point, the filesystem owning that dentry may be queried as to whether the
+ * caller is permitted to proceed or not.
+ */
+int follow_down(struct path *path)
+{
+ unsigned managed;
+ int ret;
+
+ while (managed = ACCESS_ONCE(path->dentry->d_flags),
+ unlikely(managed & DCACHE_MANAGED_DENTRY)) {
+ /* Allow the filesystem to manage the transit without i_mutex
+ * being held.
+ *
+ * We indicate to the filesystem if someone is trying to mount
+ * something here. This gives autofs the chance to deny anyone
+ * other than its daemon the right to mount on its
+ * superstructure.
+ *
+ * The filesystem may sleep at this point.
+ */
+ if (managed & DCACHE_MANAGE_TRANSIT) {
+ BUG_ON(!path->dentry->d_op);
+ BUG_ON(!path->dentry->d_op->d_manage);
+ ret = path->dentry->d_op->d_manage(
+ path->dentry, false);
+ if (ret < 0)
+ return ret == -EISDIR ? 0 : ret;
+ }
+
+ /* Transit to a mounted filesystem. */
+ if (managed & DCACHE_MOUNTED) {
+ struct vfsmount *mounted = lookup_mnt(path);
+ if (!mounted)
+ break;
+ dput(path->dentry);
+ mntput(path->mnt);
+ path->mnt = mounted;
+ path->dentry = dget(mounted->mnt_root);
+ continue;
+ }
+
+ /* Don't handle automount points here */
+ break;
+ }
+ return 0;
+}
+EXPORT_SYMBOL(follow_down);
+
+/*
+ * Skip to top of mountpoint pile in refwalk mode for follow_dotdot()
+ */
+static void follow_mount(struct path *path)
+{
+ while (d_mountpoint(path->dentry)) {
+ struct vfsmount *mounted = lookup_mnt(path);
+ if (!mounted)
+ break;
+ dput(path->dentry);
+ mntput(path->mnt);
+ path->mnt = mounted;
+ path->dentry = dget(mounted->mnt_root);
+ }
+}
+
+static void follow_dotdot(struct nameidata *nd)
+{
+ if (!nd->root.mnt)
+ set_root(nd);
+
+ while(1) {
+ struct dentry *old = nd->path.dentry;
+
+ if (nd->path.dentry == nd->root.dentry &&
+ nd->path.mnt == nd->root.mnt) {
+ break;
+ }
+ if (nd->path.dentry != nd->path.mnt->mnt_root) {
+ /* rare case of legitimate dget_parent()... */
+ nd->path.dentry = dget_parent(nd->path.dentry);
+ dput(old);
+ break;
+ }
+ if (!follow_up(&nd->path))
+ break;
+ }
+ follow_mount(&nd->path);
+ nd->inode = nd->path.dentry->d_inode;
+}
+
+/*
+ * This looks up the name in dcache, possibly revalidates the old dentry and
+ * allocates a new one if not found or not valid. In the need_lookup argument
+ * returns whether i_op->lookup is necessary.
+ *
+ * dir->d_inode->i_mutex must be held
+ */
+static struct dentry *lookup_dcache(struct qstr *name, struct dentry *dir,
+ unsigned int flags, bool *need_lookup)
+{
+ struct dentry *dentry;
+ int error;
+
+ *need_lookup = false;
+ dentry = d_lookup(dir, name);
+ if (dentry) {
+ if (dentry->d_flags & DCACHE_OP_REVALIDATE) {
+ error = d_revalidate(dentry, flags);
+ if (unlikely(error <= 0)) {
+ if (error < 0) {
+ dput(dentry);
+ return ERR_PTR(error);
+ } else {
+ d_invalidate(dentry);
+ dput(dentry);
+ dentry = NULL;
+ }
+ }
+ }
+ }
+
+ if (!dentry) {
+ dentry = d_alloc(dir, name);
+ if (unlikely(!dentry))
+ return ERR_PTR(-ENOMEM);
+
+ *need_lookup = true;
+ }
+ return dentry;
+}
+
+/*
+ * Call i_op->lookup on the dentry. The dentry must be negative and
+ * unhashed.
+ *
+ * dir->d_inode->i_mutex must be held
+ */
+static struct dentry *lookup_real(struct inode *dir, struct dentry *dentry,
+ unsigned int flags)
+{
+ struct dentry *old;
+
+ /* Don't create child dentry for a dead directory. */
+ if (unlikely(IS_DEADDIR(dir))) {
+ dput(dentry);
+ return ERR_PTR(-ENOENT);
+ }
+
+ old = dir->i_op->lookup(dir, dentry, flags);
+ if (unlikely(old)) {
+ dput(dentry);
+ dentry = old;
+ }
+ return dentry;
+}
+
+static struct dentry *__lookup_hash(struct qstr *name,
+ struct dentry *base, unsigned int flags)
+{
+ bool need_lookup;
+ struct dentry *dentry;
+
+ dentry = lookup_dcache(name, base, flags, &need_lookup);
+ if (!need_lookup)
+ return dentry;
+
+ return lookup_real(base->d_inode, dentry, flags);
+}
+
+/*
+ * It's more convoluted than I'd like it to be, but... it's still fairly
+ * small and for now I'd prefer to have fast path as straight as possible.
+ * It _is_ time-critical.
+ */
+static int lookup_fast(struct nameidata *nd,
+ struct path *path, struct inode **inode)
+{
+ struct vfsmount *mnt = nd->path.mnt;
+ struct dentry *dentry, *parent = nd->path.dentry;
+ int need_reval = 1;
+ int status = 1;
+ int err;
+
+ /*
+ * Rename seqlock is not required here because in the off chance
+ * of a false negative due to a concurrent rename, we're going to
+ * do the non-racy lookup, below.
+ */
+ if (nd->flags & LOOKUP_RCU) {
+ unsigned seq;
+ bool negative;
+ dentry = __d_lookup_rcu(parent, &nd->last, &seq);
+ if (!dentry)
+ goto unlazy;
+
+ /*
+ * This sequence count validates that the inode matches
+ * the dentry name information from lookup.
+ */
+ *inode = dentry->d_inode;
+ negative = d_is_negative(dentry);
+ if (read_seqcount_retry(&dentry->d_seq, seq))
+ return -ECHILD;
+ if (negative)
+ return -ENOENT;
+
+ /*
+ * This sequence count validates that the parent had no
+ * changes while we did the lookup of the dentry above.
+ *
+ * The memory barrier in read_seqcount_begin of child is
+ * enough, we can use __read_seqcount_retry here.
+ */
+ if (__read_seqcount_retry(&parent->d_seq, nd->seq))
+ return -ECHILD;
+ nd->seq = seq;
+
+ if (unlikely(dentry->d_flags & DCACHE_OP_REVALIDATE)) {
+ status = d_revalidate(dentry, nd->flags);
+ if (unlikely(status <= 0)) {
+ if (status != -ECHILD)
+ need_reval = 0;
+ goto unlazy;
+ }
+ }
+ path->mnt = mnt;
+ path->dentry = dentry;
+ if (likely(__follow_mount_rcu(nd, path, inode)))
+ return 0;
+unlazy:
+ if (unlazy_walk(nd, dentry))
+ return -ECHILD;
+ } else {
+ dentry = __d_lookup(parent, &nd->last);
+ }
+
+ if (unlikely(!dentry))
+ goto need_lookup;
+
+ if (unlikely(dentry->d_flags & DCACHE_OP_REVALIDATE) && need_reval)
+ status = d_revalidate(dentry, nd->flags);
+ if (unlikely(status <= 0)) {
+ if (status < 0) {
+ dput(dentry);
+ return status;
+ }
+ d_invalidate(dentry);
+ dput(dentry);
+ goto need_lookup;
+ }
+
+ if (unlikely(d_is_negative(dentry))) {
+ dput(dentry);
+ return -ENOENT;
+ }
+ path->mnt = mnt;
+ path->dentry = dentry;
+ err = follow_managed(path, nd->flags);
+ if (unlikely(err < 0)) {
+ path_put_conditional(path, nd);
+ return err;
+ }
+ if (err)
+ nd->flags |= LOOKUP_JUMPED;
+ *inode = path->dentry->d_inode;
+ return 0;
+
+need_lookup:
+ return 1;
+}
+
+/* Fast lookup failed, do it the slow way */
+static int lookup_slow(struct nameidata *nd, struct path *path)
+{
+ struct dentry *dentry, *parent;
+ int err;
+
+ parent = nd->path.dentry;
+ BUG_ON(nd->inode != parent->d_inode);
+
+ mutex_lock(&parent->d_inode->i_mutex);
+ dentry = __lookup_hash(&nd->last, parent, nd->flags);
+ mutex_unlock(&parent->d_inode->i_mutex);
+ if (IS_ERR(dentry))
+ return PTR_ERR(dentry);
+ path->mnt = nd->path.mnt;
+ path->dentry = dentry;
+ err = follow_managed(path, nd->flags);
+ if (unlikely(err < 0)) {
+ path_put_conditional(path, nd);
+ return err;
+ }
+ if (err)
+ nd->flags |= LOOKUP_JUMPED;
+ return 0;
+}
+
+static inline int may_lookup(struct nameidata *nd)
+{
+ if (nd->flags & LOOKUP_RCU) {
+ int err = inode_permission(nd->inode, MAY_EXEC|MAY_NOT_BLOCK);
+ if (err != -ECHILD)
+ return err;
+ if (unlazy_walk(nd, NULL))
+ return -ECHILD;
+ }
+ return inode_permission(nd->inode, MAY_EXEC);
+}
+
+static inline int handle_dots(struct nameidata *nd, int type)
+{
+ if (type == LAST_DOTDOT) {
+ if (nd->flags & LOOKUP_RCU) {
+ if (follow_dotdot_rcu(nd))
+ return -ECHILD;
+ } else
+ follow_dotdot(nd);
+ }
+ return 0;
+}
+
+static void terminate_walk(struct nameidata *nd)
+{
+ if (!(nd->flags & LOOKUP_RCU)) {
+ path_put(&nd->path);
+ } else {
+ nd->flags &= ~LOOKUP_RCU;
+ if (!(nd->flags & LOOKUP_ROOT))
+ nd->root.mnt = NULL;
+ rcu_read_unlock();
+ }
+}
+
+/*
+ * Do we need to follow links? We _really_ want to be able
+ * to do this check without having to look at inode->i_op,
+ * so we keep a cache of "no, this doesn't need follow_link"
+ * for the common case.
+ */
+static inline int should_follow_link(struct dentry *dentry, int follow)
+{
+ return unlikely(d_is_symlink(dentry)) ? follow : 0;
+}
+
+static inline int walk_component(struct nameidata *nd, struct path *path,
+ int follow)
+{
+ struct inode *inode;
+ int err;
+ /*
+ * "." and ".." are special - ".." especially so because it has
+ * to be able to know about the current root directory and
+ * parent relationships.
+ */
+ if (unlikely(nd->last_type != LAST_NORM))
+ return handle_dots(nd, nd->last_type);
+ err = lookup_fast(nd, path, &inode);
+ if (unlikely(err)) {
+ if (err < 0)
+ goto out_err;
+
+ err = lookup_slow(nd, path);
+ if (err < 0)
+ goto out_err;
+
+ inode = path->dentry->d_inode;
+ err = -ENOENT;
+ if (d_is_negative(path->dentry))
+ goto out_path_put;
+ }
+
+ if (should_follow_link(path->dentry, follow)) {
+ if (nd->flags & LOOKUP_RCU) {
+ if (unlikely(nd->path.mnt != path->mnt ||
+ unlazy_walk(nd, path->dentry))) {
+ err = -ECHILD;
+ goto out_err;
+ }
+ }
+ BUG_ON(inode != path->dentry->d_inode);
+ return 1;
+ }
+ path_to_nameidata(path, nd);
+ nd->inode = inode;
+ return 0;
+
+out_path_put:
+ path_to_nameidata(path, nd);
+out_err:
+ terminate_walk(nd);
+ return err;
+}
+
+/*
+ * This limits recursive symlink follows to 8, while
+ * limiting consecutive symlinks to 40.
+ *
+ * Without that kind of total limit, nasty chains of consecutive
+ * symlinks can cause almost arbitrarily long lookups.
+ */
+static inline int nested_symlink(struct path *path, struct nameidata *nd)
+{
+ int res;
+
+ if (unlikely(current->link_count >= MAX_NESTED_LINKS)) {
+ path_put_conditional(path, nd);
+ path_put(&nd->path);
+ return -ELOOP;
+ }
+ BUG_ON(nd->depth >= MAX_NESTED_LINKS);
+
+ nd->depth++;
+ current->link_count++;
+
+ do {
+ struct path link = *path;
+ void *cookie;
+
+ res = follow_link(&link, nd, &cookie);
+ if (res)
+ break;
+ res = walk_component(nd, path, LOOKUP_FOLLOW);
+ put_link(nd, &link, cookie);
+ } while (res > 0);
+
+ current->link_count--;
+ nd->depth--;
+ return res;
+}
+
+/*
+ * We can do the critical dentry name comparison and hashing
+ * operations one word at a time, but we are limited to:
+ *
+ * - Architectures with fast unaligned word accesses. We could
+ * do a "get_unaligned()" if this helps and is sufficiently
+ * fast.
+ *
+ * - non-CONFIG_DEBUG_PAGEALLOC configurations (so that we
+ * do not trap on the (extremely unlikely) case of a page
+ * crossing operation.
+ *
+ * - Furthermore, we need an efficient 64-bit compile for the
+ * 64-bit case in order to generate the "number of bytes in
+ * the final mask". Again, that could be replaced with a
+ * efficient population count instruction or similar.
+ */
+#ifdef CONFIG_DCACHE_WORD_ACCESS
+
+#include <asm/word-at-a-time.h>
+
+#ifdef CONFIG_64BIT
+
+static inline unsigned int fold_hash(unsigned long hash)
+{
+ return hash_64(hash, 32);
+}
+
+#else /* 32-bit case */
+
+#define fold_hash(x) (x)
+
+#endif
+
+unsigned int full_name_hash(const unsigned char *name, unsigned int len)
+{
+ unsigned long a, mask;
+ unsigned long hash = 0;
+
+ for (;;) {
+ a = load_unaligned_zeropad(name);
+ if (len < sizeof(unsigned long))
+ break;
+ hash += a;
+ hash *= 9;
+ name += sizeof(unsigned long);
+ len -= sizeof(unsigned long);
+ if (!len)
+ goto done;
+ }
+ mask = bytemask_from_count(len);
+ hash += mask & a;
+done:
+ return fold_hash(hash);
+}
+EXPORT_SYMBOL(full_name_hash);
+
+/*
+ * Calculate the length and hash of the path component, and
+ * return the "hash_len" as the result.
+ */
+static inline u64 hash_name(const char *name)
+{
+ unsigned long a, b, adata, bdata, mask, hash, len;
+ const struct word_at_a_time constants = WORD_AT_A_TIME_CONSTANTS;
+
+ hash = a = 0;
+ len = -sizeof(unsigned long);
+ do {
+ hash = (hash + a) * 9;
+ len += sizeof(unsigned long);
+ a = load_unaligned_zeropad(name+len);
+ b = a ^ REPEAT_BYTE('/');
+ } while (!(has_zero(a, &adata, &constants) | has_zero(b, &bdata, &constants)));
+
+ adata = prep_zero_mask(a, adata, &constants);
+ bdata = prep_zero_mask(b, bdata, &constants);
+
+ mask = create_zero_mask(adata | bdata);
+
+ hash += a & zero_bytemask(mask);
+ len += find_zero(mask);
+ return hashlen_create(fold_hash(hash), len);
+}
+
+#else
+
+unsigned int full_name_hash(const unsigned char *name, unsigned int len)
+{
+ unsigned long hash = init_name_hash();
+ while (len--)
+ hash = partial_name_hash(*name++, hash);
+ return end_name_hash(hash);
+}
+EXPORT_SYMBOL(full_name_hash);
+
+/*
+ * We know there's a real path component here of at least
+ * one character.
+ */
+static inline u64 hash_name(const char *name)
+{
+ unsigned long hash = init_name_hash();
+ unsigned long len = 0, c;
+
+ c = (unsigned char)*name;
+ do {
+ len++;
+ hash = partial_name_hash(c, hash);
+ c = (unsigned char)name[len];
+ } while (c && c != '/');
+ return hashlen_create(end_name_hash(hash), len);
+}
+
+#endif
+
+/*
+ * Name resolution.
+ * This is the basic name resolution function, turning a pathname into
+ * the final dentry. We expect 'base' to be positive and a directory.
+ *
+ * Returns 0 and nd will have valid dentry and mnt on success.
+ * Returns error and drops reference to input namei data on failure.
+ */
+static int link_path_walk(const char *name, struct nameidata *nd)
+{
+ struct path next;
+ int err;
+
+ while (*name=='/')
+ name++;
+ if (!*name)
+ return 0;
+
+ /* At this point we know we have a real path component. */
+ for(;;) {
+ u64 hash_len;
+ int type;
+
+ err = may_lookup(nd);
+ if (err)
+ break;
+
+ hash_len = hash_name(name);
+
+ type = LAST_NORM;
+ if (name[0] == '.') switch (hashlen_len(hash_len)) {
+ case 2:
+ if (name[1] == '.') {
+ type = LAST_DOTDOT;
+ nd->flags |= LOOKUP_JUMPED;
+ }
+ break;
+ case 1:
+ type = LAST_DOT;
+ }
+ if (likely(type == LAST_NORM)) {
+ struct dentry *parent = nd->path.dentry;
+ nd->flags &= ~LOOKUP_JUMPED;
+ if (unlikely(parent->d_flags & DCACHE_OP_HASH)) {
+ struct qstr this = { { .hash_len = hash_len }, .name = name };
+ err = parent->d_op->d_hash(parent, &this);
+ if (err < 0)
+ break;
+ hash_len = this.hash_len;
+ name = this.name;
+ }
+ }
+
+ nd->last.hash_len = hash_len;
+ nd->last.name = name;
+ nd->last_type = type;
+
+ name += hashlen_len(hash_len);
+ if (!*name)
+ return 0;
+ /*
+ * If it wasn't NUL, we know it was '/'. Skip that
+ * slash, and continue until no more slashes.
+ */
+ do {
+ name++;
+ } while (unlikely(*name == '/'));
+ if (!*name)
+ return 0;
+
+ err = walk_component(nd, &next, LOOKUP_FOLLOW);
+ if (err < 0)
+ return err;
+
+ if (err) {
+ err = nested_symlink(&next, nd);
+ if (err)
+ return err;
+ }
+ if (!d_can_lookup(nd->path.dentry)) {
+ err = -ENOTDIR;
+ break;
+ }
+ }
+ terminate_walk(nd);
+ return err;
+}
+
+static int path_init(int dfd, const struct filename *name, unsigned int flags,
+ struct nameidata *nd)
+{
+ int retval = 0;
+ const char *s = name->name;
+
+ nd->last_type = LAST_ROOT; /* if there are only slashes... */
+ nd->flags = flags | LOOKUP_JUMPED | LOOKUP_PARENT;
+ nd->depth = 0;
+ nd->base = NULL;
+ if (flags & LOOKUP_ROOT) {
+ struct dentry *root = nd->root.dentry;
+ struct inode *inode = root->d_inode;
+ if (*s) {
+ if (!d_can_lookup(root))
+ return -ENOTDIR;
+ retval = inode_permission(inode, MAY_EXEC);
+ if (retval)
+ return retval;
+ }
+ nd->path = nd->root;
+ nd->inode = inode;
+ if (flags & LOOKUP_RCU) {
+ rcu_read_lock();
+ nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq);
+ nd->m_seq = read_seqbegin(&mount_lock);
+ } else {
+ path_get(&nd->path);
+ }
+ goto done;
+ }
+
+ nd->root.mnt = NULL;
+
+ nd->m_seq = read_seqbegin(&mount_lock);
+ if (*s == '/') {
+ if (flags & LOOKUP_RCU) {
+ rcu_read_lock();
+ nd->seq = set_root_rcu(nd);
+ } else {
+ set_root(nd);
+ path_get(&nd->root);
+ }
+ nd->path = nd->root;
+ } else if (dfd == AT_FDCWD) {
+ if (flags & LOOKUP_RCU) {
+ struct fs_struct *fs = current->fs;
+ unsigned seq;
+
+ rcu_read_lock();
+
+ do {
+ seq = read_seqcount_begin(&fs->seq);
+ nd->path = fs->pwd;
+ nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq);
+ } while (read_seqcount_retry(&fs->seq, seq));
+ } else {
+ get_fs_pwd(current->fs, &nd->path);
+ }
+ } else {
+ /* Caller must check execute permissions on the starting path component */
+ struct fd f = fdget_raw(dfd);
+ struct dentry *dentry;
+
+ if (!f.file)
+ return -EBADF;
+
+ dentry = f.file->f_path.dentry;
+
+ if (*s) {
+ if (!d_can_lookup(dentry)) {
+ fdput(f);
+ return -ENOTDIR;
+ }
+ }
+
+ nd->path = f.file->f_path;
+ if (flags & LOOKUP_RCU) {
+ if (f.flags & FDPUT_FPUT)
+ nd->base = f.file;
+ nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq);
+ rcu_read_lock();
+ } else {
+ path_get(&nd->path);
+ fdput(f);
+ }
+ }
+
+ nd->inode = nd->path.dentry->d_inode;
+ if (!(flags & LOOKUP_RCU))
+ goto done;
+ if (likely(!read_seqcount_retry(&nd->path.dentry->d_seq, nd->seq)))
+ goto done;
+ if (!(nd->flags & LOOKUP_ROOT))
+ nd->root.mnt = NULL;
+ rcu_read_unlock();
+ return -ECHILD;
+done:
+ current->total_link_count = 0;
+ return link_path_walk(s, nd);
+}
+
+static void path_cleanup(struct nameidata *nd)
+{
+ if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT)) {
+ path_put(&nd->root);
+ nd->root.mnt = NULL;
+ }
+ if (unlikely(nd->base))
+ fput(nd->base);
+}
+
+static inline int lookup_last(struct nameidata *nd, struct path *path)
+{
+ if (nd->last_type == LAST_NORM && nd->last.name[nd->last.len])
+ nd->flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
+
+ nd->flags &= ~LOOKUP_PARENT;
+ return walk_component(nd, path, nd->flags & LOOKUP_FOLLOW);
+}
+
+/* Returns 0 and nd will be valid on success; Retuns error, otherwise. */
+static int path_lookupat(int dfd, const struct filename *name,
+ unsigned int flags, struct nameidata *nd)
+{
+ struct path path;
+ int err;
+
+ /*
+ * Path walking is largely split up into 2 different synchronisation
+ * schemes, rcu-walk and ref-walk (explained in
+ * Documentation/filesystems/path-lookup.txt). These share much of the
+ * path walk code, but some things particularly setup, cleanup, and
+ * following mounts are sufficiently divergent that functions are
+ * duplicated. Typically there is a function foo(), and its RCU
+ * analogue, foo_rcu().
+ *
+ * -ECHILD is the error number of choice (just to avoid clashes) that
+ * is returned if some aspect of an rcu-walk fails. Such an error must
+ * be handled by restarting a traditional ref-walk (which will always
+ * be able to complete).
+ */
+ err = path_init(dfd, name, flags, nd);
+ if (!err && !(flags & LOOKUP_PARENT)) {
+ err = lookup_last(nd, &path);
+ while (err > 0) {
+ void *cookie;
+ struct path link = path;
+ err = may_follow_link(&link, nd);
+ if (unlikely(err))
+ break;
+ nd->flags |= LOOKUP_PARENT;
+ err = follow_link(&link, nd, &cookie);
+ if (err)
+ break;
+ err = lookup_last(nd, &path);
+ put_link(nd, &link, cookie);
+ }
+ }
+
+ if (!err)
+ err = complete_walk(nd);
+
+ if (!err && nd->flags & LOOKUP_DIRECTORY) {
+ if (!d_can_lookup(nd->path.dentry)) {
+ path_put(&nd->path);
+ err = -ENOTDIR;
+ }
+ }
+
+ path_cleanup(nd);
+ return err;
+}
+
+static int filename_lookup(int dfd, struct filename *name,
+ unsigned int flags, struct nameidata *nd)
+{
+ int retval = path_lookupat(dfd, name, flags | LOOKUP_RCU, nd);
+ if (unlikely(retval == -ECHILD))
+ retval = path_lookupat(dfd, name, flags, nd);
+ if (unlikely(retval == -ESTALE))
+ retval = path_lookupat(dfd, name, flags | LOOKUP_REVAL, nd);
+
+ if (likely(!retval))
+ audit_inode(name, nd->path.dentry, flags & LOOKUP_PARENT);
+ return retval;
+}
+
+/* does lookup, returns the object with parent locked */
+struct dentry *kern_path_locked(const char *name, struct path *path)
+{
+ struct filename *filename = getname_kernel(name);
+ struct nameidata nd;
+ struct dentry *d;
+ int err;
+
+ if (IS_ERR(filename))
+ return ERR_CAST(filename);
+
+ err = filename_lookup(AT_FDCWD, filename, LOOKUP_PARENT, &nd);
+ if (err) {
+ d = ERR_PTR(err);
+ goto out;
+ }
+ if (nd.last_type != LAST_NORM) {
+ path_put(&nd.path);
+ d = ERR_PTR(-EINVAL);
+ goto out;
+ }
+ mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
+ d = __lookup_hash(&nd.last, nd.path.dentry, 0);
+ if (IS_ERR(d)) {
+ mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
+ path_put(&nd.path);
+ goto out;
+ }
+ *path = nd.path;
+out:
+ putname(filename);
+ return d;
+}
+
+int kern_path(const char *name, unsigned int flags, struct path *path)
+{
+ struct nameidata nd;
+ struct filename *filename = getname_kernel(name);
+ int res = PTR_ERR(filename);
+
+ if (!IS_ERR(filename)) {
+ res = filename_lookup(AT_FDCWD, filename, flags, &nd);
+ putname(filename);
+ if (!res)
+ *path = nd.path;
+ }
+ return res;
+}
+EXPORT_SYMBOL(kern_path);
+
+/**
+ * vfs_path_lookup - lookup a file path relative to a dentry-vfsmount pair
+ * @dentry: pointer to dentry of the base directory
+ * @mnt: pointer to vfs mount of the base directory
+ * @name: pointer to file name
+ * @flags: lookup flags
+ * @path: pointer to struct path to fill
+ */
+int vfs_path_lookup(struct dentry *dentry, struct vfsmount *mnt,
+ const char *name, unsigned int flags,
+ struct path *path)
+{
+ struct filename *filename = getname_kernel(name);
+ int err = PTR_ERR(filename);
+
+ BUG_ON(flags & LOOKUP_PARENT);
+
+ /* the first argument of filename_lookup() is ignored with LOOKUP_ROOT */
+ if (!IS_ERR(filename)) {
+ struct nameidata nd;
+ nd.root.dentry = dentry;
+ nd.root.mnt = mnt;
+ err = filename_lookup(AT_FDCWD, filename,
+ flags | LOOKUP_ROOT, &nd);
+ if (!err)
+ *path = nd.path;
+ putname(filename);
+ }
+ return err;
+}
+EXPORT_SYMBOL(vfs_path_lookup);
+
+/*
+ * Restricted form of lookup. Doesn't follow links, single-component only,
+ * needs parent already locked. Doesn't follow mounts.
+ * SMP-safe.
+ */
+static struct dentry *lookup_hash(struct nameidata *nd)
+{
+ return __lookup_hash(&nd->last, nd->path.dentry, nd->flags);
+}
+
+/**
+ * lookup_one_len - filesystem helper to lookup single pathname component
+ * @name: pathname component to lookup
+ * @base: base directory to lookup from
+ * @len: maximum length @len should be interpreted to
+ *
+ * Note that this routine is purely a helper for filesystem usage and should
+ * not be called by generic code.
+ */
+struct dentry *lookup_one_len(const char *name, struct dentry *base, int len)
+{
+ struct qstr this;
+ unsigned int c;
+ int err;
+
+ WARN_ON_ONCE(!mutex_is_locked(&base->d_inode->i_mutex));
+
+ this.name = name;
+ this.len = len;
+ this.hash = full_name_hash(name, len);
+ if (!len)
+ return ERR_PTR(-EACCES);
+
+ if (unlikely(name[0] == '.')) {
+ if (len < 2 || (len == 2 && name[1] == '.'))
+ return ERR_PTR(-EACCES);
+ }
+
+ while (len--) {
+ c = *(const unsigned char *)name++;
+ if (c == '/' || c == '\0')
+ return ERR_PTR(-EACCES);
+ }
+ /*
+ * See if the low-level filesystem might want
+ * to use its own hash..
+ */
+ if (base->d_flags & DCACHE_OP_HASH) {
+ int err = base->d_op->d_hash(base, &this);
+ if (err < 0)
+ return ERR_PTR(err);
+ }
+
+ err = inode_permission(base->d_inode, MAY_EXEC);
+ if (err)
+ return ERR_PTR(err);
+
+ return __lookup_hash(&this, base, 0);
+}
+EXPORT_SYMBOL(lookup_one_len);
+
+int user_path_at_empty(int dfd, const char __user *name, unsigned flags,
+ struct path *path, int *empty)
+{
+ struct nameidata nd;
+ struct filename *tmp = getname_flags(name, flags, empty);
+ int err = PTR_ERR(tmp);
+ if (!IS_ERR(tmp)) {
+
+ BUG_ON(flags & LOOKUP_PARENT);
+
+ err = filename_lookup(dfd, tmp, flags, &nd);
+ putname(tmp);
+ if (!err)
+ *path = nd.path;
+ }
+ return err;
+}
+
+int user_path_at(int dfd, const char __user *name, unsigned flags,
+ struct path *path)
+{
+ return user_path_at_empty(dfd, name, flags, path, NULL);
+}
+EXPORT_SYMBOL(user_path_at);
+
+/*
+ * NB: most callers don't do anything directly with the reference to the
+ * to struct filename, but the nd->last pointer points into the name string
+ * allocated by getname. So we must hold the reference to it until all
+ * path-walking is complete.
+ */
+static struct filename *
+user_path_parent(int dfd, const char __user *path, struct nameidata *nd,
+ unsigned int flags)
+{
+ struct filename *s = getname(path);
+ int error;
+
+ /* only LOOKUP_REVAL is allowed in extra flags */
+ flags &= LOOKUP_REVAL;
+
+ if (IS_ERR(s))
+ return s;
+
+ error = filename_lookup(dfd, s, flags | LOOKUP_PARENT, nd);
+ if (error) {
+ putname(s);
+ return ERR_PTR(error);
+ }
+
+ return s;
+}
+
+/**
+ * mountpoint_last - look up last component for umount
+ * @nd: pathwalk nameidata - currently pointing at parent directory of "last"
+ * @path: pointer to container for result
+ *
+ * This is a special lookup_last function just for umount. In this case, we
+ * need to resolve the path without doing any revalidation.
+ *
+ * The nameidata should be the result of doing a LOOKUP_PARENT pathwalk. Since
+ * mountpoints are always pinned in the dcache, their ancestors are too. Thus,
+ * in almost all cases, this lookup will be served out of the dcache. The only
+ * cases where it won't are if nd->last refers to a symlink or the path is
+ * bogus and it doesn't exist.
+ *
+ * Returns:
+ * -error: if there was an error during lookup. This includes -ENOENT if the
+ * lookup found a negative dentry. The nd->path reference will also be
+ * put in this case.
+ *
+ * 0: if we successfully resolved nd->path and found it to not to be a
+ * symlink that needs to be followed. "path" will also be populated.
+ * The nd->path reference will also be put.
+ *
+ * 1: if we successfully resolved nd->last and found it to be a symlink
+ * that needs to be followed. "path" will be populated with the path
+ * to the link, and nd->path will *not* be put.
+ */
+static int
+mountpoint_last(struct nameidata *nd, struct path *path)
+{
+ int error = 0;
+ struct dentry *dentry;
+ struct dentry *dir = nd->path.dentry;
+
+ /* If we're in rcuwalk, drop out of it to handle last component */
+ if (nd->flags & LOOKUP_RCU) {
+ if (unlazy_walk(nd, NULL)) {
+ error = -ECHILD;
+ goto out;
+ }
+ }
+
+ nd->flags &= ~LOOKUP_PARENT;
+
+ if (unlikely(nd->last_type != LAST_NORM)) {
+ error = handle_dots(nd, nd->last_type);
+ if (error)
+ goto out;
+ dentry = dget(nd->path.dentry);
+ goto done;
+ }
+
+ mutex_lock(&dir->d_inode->i_mutex);
+ dentry = d_lookup(dir, &nd->last);
+ if (!dentry) {
+ /*
+ * No cached dentry. Mounted dentries are pinned in the cache,
+ * so that means that this dentry is probably a symlink or the
+ * path doesn't actually point to a mounted dentry.
+ */
+ dentry = d_alloc(dir, &nd->last);
+ if (!dentry) {
+ error = -ENOMEM;
+ mutex_unlock(&dir->d_inode->i_mutex);
+ goto out;
+ }
+ dentry = lookup_real(dir->d_inode, dentry, nd->flags);
+ error = PTR_ERR(dentry);
+ if (IS_ERR(dentry)) {
+ mutex_unlock(&dir->d_inode->i_mutex);
+ goto out;
+ }
+ }
+ mutex_unlock(&dir->d_inode->i_mutex);
+
+done:
+ if (d_is_negative(dentry)) {
+ error = -ENOENT;
+ dput(dentry);
+ goto out;
+ }
+ path->dentry = dentry;
+ path->mnt = nd->path.mnt;
+ if (should_follow_link(dentry, nd->flags & LOOKUP_FOLLOW))
+ return 1;
+ mntget(path->mnt);
+ follow_mount(path);
+ error = 0;
+out:
+ terminate_walk(nd);
+ return error;
+}
+
+/**
+ * path_mountpoint - look up a path to be umounted
+ * @dfd: directory file descriptor to start walk from
+ * @name: full pathname to walk
+ * @path: pointer to container for result
+ * @flags: lookup flags
+ *
+ * Look up the given name, but don't attempt to revalidate the last component.
+ * Returns 0 and "path" will be valid on success; Returns error otherwise.
+ */
+static int
+path_mountpoint(int dfd, const struct filename *name, struct path *path,
+ unsigned int flags)
+{
+ struct nameidata nd;
+ int err;
+
+ err = path_init(dfd, name, flags, &nd);
+ if (unlikely(err))
+ goto out;
+
+ err = mountpoint_last(&nd, path);
+ while (err > 0) {
+ void *cookie;
+ struct path link = *path;
+ err = may_follow_link(&link, &nd);
+ if (unlikely(err))
+ break;
+ nd.flags |= LOOKUP_PARENT;
+ err = follow_link(&link, &nd, &cookie);
+ if (err)
+ break;
+ err = mountpoint_last(&nd, path);
+ put_link(&nd, &link, cookie);
+ }
+out:
+ path_cleanup(&nd);
+ return err;
+}
+
+static int
+filename_mountpoint(int dfd, struct filename *name, struct path *path,
+ unsigned int flags)
+{
+ int error;
+ if (IS_ERR(name))
+ return PTR_ERR(name);
+ error = path_mountpoint(dfd, name, path, flags | LOOKUP_RCU);
+ if (unlikely(error == -ECHILD))
+ error = path_mountpoint(dfd, name, path, flags);
+ if (unlikely(error == -ESTALE))
+ error = path_mountpoint(dfd, name, path, flags | LOOKUP_REVAL);
+ if (likely(!error))
+ audit_inode(name, path->dentry, 0);
+ putname(name);
+ return error;
+}
+
+/**
+ * user_path_mountpoint_at - lookup a path from userland in order to umount it
+ * @dfd: directory file descriptor
+ * @name: pathname from userland
+ * @flags: lookup flags
+ * @path: pointer to container to hold result
+ *
+ * A umount is a special case for path walking. We're not actually interested
+ * in the inode in this situation, and ESTALE errors can be a problem. We
+ * simply want track down the dentry and vfsmount attached at the mountpoint
+ * and avoid revalidating the last component.
+ *
+ * Returns 0 and populates "path" on success.
+ */
+int
+user_path_mountpoint_at(int dfd, const char __user *name, unsigned int flags,
+ struct path *path)
+{
+ return filename_mountpoint(dfd, getname(name), path, flags);
+}
+
+int
+kern_path_mountpoint(int dfd, const char *name, struct path *path,
+ unsigned int flags)
+{
+ return filename_mountpoint(dfd, getname_kernel(name), path, flags);
+}
+EXPORT_SYMBOL(kern_path_mountpoint);
+
+int __check_sticky(struct inode *dir, struct inode *inode)
+{
+ kuid_t fsuid = current_fsuid();
+
+ if (uid_eq(inode->i_uid, fsuid))
+ return 0;
+ if (uid_eq(dir->i_uid, fsuid))
+ return 0;
+ return !capable_wrt_inode_uidgid(inode, CAP_FOWNER);
+}
+EXPORT_SYMBOL(__check_sticky);
+
+/*
+ * Check whether we can remove a link victim from directory dir, check
+ * whether the type of victim is right.
+ * 1. We can't do it if dir is read-only (done in permission())
+ * 2. We should have write and exec permissions on dir
+ * 3. We can't remove anything from append-only dir
+ * 4. We can't do anything with immutable dir (done in permission())
+ * 5. If the sticky bit on dir is set we should either
+ * a. be owner of dir, or
+ * b. be owner of victim, or
+ * c. have CAP_FOWNER capability
+ * 6. If the victim is append-only or immutable we can't do antyhing with
+ * links pointing to it.
+ * 7. If we were asked to remove a directory and victim isn't one - ENOTDIR.
+ * 8. If we were asked to remove a non-directory and victim isn't one - EISDIR.
+ * 9. We can't remove a root or mountpoint.
+ * 10. We don't allow removal of NFS sillyrenamed files; it's handled by
+ * nfs_async_unlink().
+ */
+static int may_delete(struct inode *dir, struct dentry *victim, bool isdir)
+{
+ struct inode *inode = victim->d_inode;
+ int error;
+
+ if (d_is_negative(victim))
+ return -ENOENT;
+ BUG_ON(!inode);
+
+ BUG_ON(victim->d_parent->d_inode != dir);
+ audit_inode_child(dir, victim, AUDIT_TYPE_CHILD_DELETE);
+
+ error = inode_permission(dir, MAY_WRITE | MAY_EXEC);
+ if (error)
+ return error;
+ if (IS_APPEND(dir))
+ return -EPERM;
+
+ if (check_sticky(dir, inode) || IS_APPEND(inode) ||
+ IS_IMMUTABLE(inode) || IS_SWAPFILE(inode))
+ return -EPERM;
+ if (isdir) {
+ if (!d_is_dir(victim))
+ return -ENOTDIR;
+ if (IS_ROOT(victim))
+ return -EBUSY;
+ } else if (d_is_dir(victim))
+ return -EISDIR;
+ if (IS_DEADDIR(dir))
+ return -ENOENT;
+ if (victim->d_flags & DCACHE_NFSFS_RENAMED)
+ return -EBUSY;
+ return 0;
+}
+
+/* Check whether we can create an object with dentry child in directory
+ * dir.
+ * 1. We can't do it if child already exists (open has special treatment for
+ * this case, but since we are inlined it's OK)
+ * 2. We can't do it if dir is read-only (done in permission())
+ * 3. We should have write and exec permissions on dir
+ * 4. We can't do it if dir is immutable (done in permission())
+ */
+static inline int may_create(struct inode *dir, struct dentry *child)
+{
+ audit_inode_child(dir, child, AUDIT_TYPE_CHILD_CREATE);
+ if (child->d_inode)
+ return -EEXIST;
+ if (IS_DEADDIR(dir))
+ return -ENOENT;
+ return inode_permission(dir, MAY_WRITE | MAY_EXEC);
+}
+
+/*
+ * p1 and p2 should be directories on the same fs.
+ */
+struct dentry *lock_rename(struct dentry *p1, struct dentry *p2)
+{
+ struct dentry *p;
+
+ if (p1 == p2) {
+ mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT);
+ return NULL;
+ }
+
+ mutex_lock(&p1->d_inode->i_sb->s_vfs_rename_mutex);
+
+ p = d_ancestor(p2, p1);
+ if (p) {
+ mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_PARENT);
+ mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_CHILD);
+ return p;
+ }
+
+ p = d_ancestor(p1, p2);
+ if (p) {
+ mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT);
+ mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_CHILD);
+ return p;
+ }
+
+ mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT);
+ mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_PARENT2);
+ return NULL;
+}
+EXPORT_SYMBOL(lock_rename);
+
+void unlock_rename(struct dentry *p1, struct dentry *p2)
+{
+ mutex_unlock(&p1->d_inode->i_mutex);
+ if (p1 != p2) {
+ mutex_unlock(&p2->d_inode->i_mutex);
+ mutex_unlock(&p1->d_inode->i_sb->s_vfs_rename_mutex);
+ }
+}
+EXPORT_SYMBOL(unlock_rename);
+
+int vfs_create(struct inode *dir, struct dentry *dentry, umode_t mode,
+ bool want_excl)
+{
+ int error = may_create(dir, dentry);
+ if (error)
+ return error;
+
+ if (!dir->i_op->create)
+ return -EACCES; /* shouldn't it be ENOSYS? */
+ mode &= S_IALLUGO;
+ mode |= S_IFREG;
+ error = security_inode_create(dir, dentry, mode);
+ if (error)
+ return error;
+ error = dir->i_op->create(dir, dentry, mode, want_excl);
+ if (!error)
+ fsnotify_create(dir, dentry);
+ return error;
+}
+EXPORT_SYMBOL(vfs_create);
+
+static int may_open(struct path *path, int acc_mode, int flag)
+{
+ struct dentry *dentry = path->dentry;
+ struct inode *inode = dentry->d_inode;
+ int error;
+
+ /* O_PATH? */
+ if (!acc_mode)
+ return 0;
+
+ if (!inode)
+ return -ENOENT;
+
+ switch (inode->i_mode & S_IFMT) {
+ case S_IFLNK:
+ return -ELOOP;
+ case S_IFDIR:
+ if (acc_mode & MAY_WRITE)
+ return -EISDIR;
+ break;
+ case S_IFBLK:
+ case S_IFCHR:
+ if (path->mnt->mnt_flags & MNT_NODEV)
+ return -EACCES;
+ /*FALLTHRU*/
+ case S_IFIFO:
+ case S_IFSOCK:
+ flag &= ~O_TRUNC;
+ break;
+ }
+
+ error = inode_permission(inode, acc_mode);
+ if (error)
+ return error;
+
+ /*
+ * An append-only file must be opened in append mode for writing.
+ */
+ if (IS_APPEND(inode)) {
+ if ((flag & O_ACCMODE) != O_RDONLY && !(flag & O_APPEND))
+ return -EPERM;
+ if (flag & O_TRUNC)
+ return -EPERM;
+ }
+
+ /* O_NOATIME can only be set by the owner or superuser */
+ if (flag & O_NOATIME && !inode_owner_or_capable(inode))
+ return -EPERM;
+
+ return 0;
+}
+
+static int handle_truncate(struct file *filp)
+{
+ struct path *path = &filp->f_path;
+ struct inode *inode = path->dentry->d_inode;
+ int error = get_write_access(inode);
+ if (error)
+ return error;
+ /*
+ * Refuse to truncate files with mandatory locks held on them.
+ */
+ error = locks_verify_locked(filp);
+ if (!error)
+ error = security_path_truncate(path);
+ if (!error) {
+ error = do_truncate(path->dentry, 0,
+ ATTR_MTIME|ATTR_CTIME|ATTR_OPEN,
+ filp);
+ }
+ put_write_access(inode);
+ return error;
+}
+
+static inline int open_to_namei_flags(int flag)
+{
+ if ((flag & O_ACCMODE) == 3)
+ flag--;
+ return flag;
+}
+
+static int may_o_create(struct path *dir, struct dentry *dentry, umode_t mode)
+{
+ int error = security_path_mknod(dir, dentry, mode, 0);
+ if (error)
+ return error;
+
+ error = inode_permission(dir->dentry->d_inode, MAY_WRITE | MAY_EXEC);
+ if (error)
+ return error;
+
+ return security_inode_create(dir->dentry->d_inode, dentry, mode);
+}
+
+/*
+ * Attempt to atomically look up, create and open a file from a negative
+ * dentry.
+ *
+ * Returns 0 if successful. The file will have been created and attached to
+ * @file by the filesystem calling finish_open().
+ *
+ * Returns 1 if the file was looked up only or didn't need creating. The
+ * caller will need to perform the open themselves. @path will have been
+ * updated to point to the new dentry. This may be negative.
+ *
+ * Returns an error code otherwise.
+ */
+static int atomic_open(struct nameidata *nd, struct dentry *dentry,
+ struct path *path, struct file *file,
+ const struct open_flags *op,
+ bool got_write, bool need_lookup,
+ int *opened)
+{
+ struct inode *dir = nd->path.dentry->d_inode;
+ unsigned open_flag = open_to_namei_flags(op->open_flag);
+ umode_t mode;
+ int error;
+ int acc_mode;
+ int create_error = 0;
+ struct dentry *const DENTRY_NOT_SET = (void *) -1UL;
+ bool excl;
+
+ BUG_ON(dentry->d_inode);
+
+ /* Don't create child dentry for a dead directory. */
+ if (unlikely(IS_DEADDIR(dir))) {
+ error = -ENOENT;
+ goto out;
+ }
+
+ mode = op->mode;
+ if ((open_flag & O_CREAT) && !IS_POSIXACL(dir))
+ mode &= ~current_umask();
+
+ excl = (open_flag & (O_EXCL | O_CREAT)) == (O_EXCL | O_CREAT);
+ if (excl)
+ open_flag &= ~O_TRUNC;
+
+ /*
+ * Checking write permission is tricky, bacuse we don't know if we are
+ * going to actually need it: O_CREAT opens should work as long as the
+ * file exists. But checking existence breaks atomicity. The trick is
+ * to check access and if not granted clear O_CREAT from the flags.
+ *
+ * Another problem is returing the "right" error value (e.g. for an
+ * O_EXCL open we want to return EEXIST not EROFS).
+ */
+ if (((open_flag & (O_CREAT | O_TRUNC)) ||
+ (open_flag & O_ACCMODE) != O_RDONLY) && unlikely(!got_write)) {
+ if (!(open_flag & O_CREAT)) {
+ /*
+ * No O_CREATE -> atomicity not a requirement -> fall
+ * back to lookup + open
+ */
+ goto no_open;
+ } else if (open_flag & (O_EXCL | O_TRUNC)) {
+ /* Fall back and fail with the right error */
+ create_error = -EROFS;
+ goto no_open;
+ } else {
+ /* No side effects, safe to clear O_CREAT */
+ create_error = -EROFS;
+ open_flag &= ~O_CREAT;
+ }
+ }
+
+ if (open_flag & O_CREAT) {
+ error = may_o_create(&nd->path, dentry, mode);
+ if (error) {
+ create_error = error;
+ if (open_flag & O_EXCL)
+ goto no_open;
+ open_flag &= ~O_CREAT;
+ }
+ }
+
+ if (nd->flags & LOOKUP_DIRECTORY)
+ open_flag |= O_DIRECTORY;
+
+ file->f_path.dentry = DENTRY_NOT_SET;
+ file->f_path.mnt = nd->path.mnt;
+ error = dir->i_op->atomic_open(dir, dentry, file, open_flag, mode,
+ opened);
+ if (error < 0) {
+ if (create_error && error == -ENOENT)
+ error = create_error;
+ goto out;
+ }
+
+ if (error) { /* returned 1, that is */
+ if (WARN_ON(file->f_path.dentry == DENTRY_NOT_SET)) {
+ error = -EIO;
+ goto out;
+ }
+ if (file->f_path.dentry) {
+ dput(dentry);
+ dentry = file->f_path.dentry;
+ }
+ if (*opened & FILE_CREATED)
+ fsnotify_create(dir, dentry);
+ if (!dentry->d_inode) {
+ WARN_ON(*opened & FILE_CREATED);
+ if (create_error) {
+ error = create_error;
+ goto out;
+ }
+ } else {
+ if (excl && !(*opened & FILE_CREATED)) {
+ error = -EEXIST;
+ goto out;
+ }
+ }
+ goto looked_up;
+ }
+
+ /*
+ * We didn't have the inode before the open, so check open permission
+ * here.
+ */
+ acc_mode = op->acc_mode;
+ if (*opened & FILE_CREATED) {
+ WARN_ON(!(open_flag & O_CREAT));
+ fsnotify_create(dir, dentry);
+ acc_mode = MAY_OPEN;
+ }
+ error = may_open(&file->f_path, acc_mode, open_flag);
+ if (error)
+ fput(file);
+
+out:
+ dput(dentry);
+ return error;
+
+no_open:
+ if (need_lookup) {
+ dentry = lookup_real(dir, dentry, nd->flags);
+ if (IS_ERR(dentry))
+ return PTR_ERR(dentry);
+
+ if (create_error) {
+ int open_flag = op->open_flag;
+
+ error = create_error;
+ if ((open_flag & O_EXCL)) {
+ if (!dentry->d_inode)
+ goto out;
+ } else if (!dentry->d_inode) {
+ goto out;
+ } else if ((open_flag & O_TRUNC) &&
+ d_is_reg(dentry)) {
+ goto out;
+ }
+ /* will fail later, go on to get the right error */
+ }
+ }
+looked_up:
+ path->dentry = dentry;
+ path->mnt = nd->path.mnt;
+ return 1;
+}
+
+/*
+ * Look up and maybe create and open the last component.
+ *
+ * Must be called with i_mutex held on parent.
+ *
+ * Returns 0 if the file was successfully atomically created (if necessary) and
+ * opened. In this case the file will be returned attached to @file.
+ *
+ * Returns 1 if the file was not completely opened at this time, though lookups
+ * and creations will have been performed and the dentry returned in @path will
+ * be positive upon return if O_CREAT was specified. If O_CREAT wasn't
+ * specified then a negative dentry may be returned.
+ *
+ * An error code is returned otherwise.
+ *
+ * FILE_CREATE will be set in @*opened if the dentry was created and will be
+ * cleared otherwise prior to returning.
+ */
+static int lookup_open(struct nameidata *nd, struct path *path,
+ struct file *file,
+ const struct open_flags *op,
+ bool got_write, int *opened)
+{
+ struct dentry *dir = nd->path.dentry;
+ struct inode *dir_inode = dir->d_inode;
+ struct dentry *dentry;
+ int error;
+ bool need_lookup;
+
+ *opened &= ~FILE_CREATED;
+ dentry = lookup_dcache(&nd->last, dir, nd->flags, &need_lookup);
+ if (IS_ERR(dentry))
+ return PTR_ERR(dentry);
+
+ /* Cached positive dentry: will open in f_op->open */
+ if (!need_lookup && dentry->d_inode)
+ goto out_no_open;
+
+ if ((nd->flags & LOOKUP_OPEN) && dir_inode->i_op->atomic_open) {
+ return atomic_open(nd, dentry, path, file, op, got_write,
+ need_lookup, opened);
+ }
+
+ if (need_lookup) {
+ BUG_ON(dentry->d_inode);
+
+ dentry = lookup_real(dir_inode, dentry, nd->flags);
+ if (IS_ERR(dentry))
+ return PTR_ERR(dentry);
+ }
+
+ /* Negative dentry, just create the file */
+ if (!dentry->d_inode && (op->open_flag & O_CREAT)) {
+ umode_t mode = op->mode;
+ if (!IS_POSIXACL(dir->d_inode))
+ mode &= ~current_umask();
+ /*
+ * This write is needed to ensure that a
+ * rw->ro transition does not occur between
+ * the time when the file is created and when
+ * a permanent write count is taken through
+ * the 'struct file' in finish_open().
+ */
+ if (!got_write) {
+ error = -EROFS;
+ goto out_dput;
+ }
+ *opened |= FILE_CREATED;
+ error = security_path_mknod(&nd->path, dentry, mode, 0);
+ if (error)
+ goto out_dput;
+ error = vfs_create(dir->d_inode, dentry, mode,
+ nd->flags & LOOKUP_EXCL);
+ if (error)
+ goto out_dput;
+ }
+out_no_open:
+ path->dentry = dentry;
+ path->mnt = nd->path.mnt;
+ return 1;
+
+out_dput:
+ dput(dentry);
+ return error;
+}
+
+/*
+ * Handle the last step of open()
+ */
+static int do_last(struct nameidata *nd, struct path *path,
+ struct file *file, const struct open_flags *op,
+ int *opened, struct filename *name)
+{
+ struct dentry *dir = nd->path.dentry;
+ int open_flag = op->open_flag;
+ bool will_truncate = (open_flag & O_TRUNC) != 0;
+ bool got_write = false;
+ int acc_mode = op->acc_mode;
+ struct inode *inode;
+ bool symlink_ok = false;
+ struct path save_parent = { .dentry = NULL, .mnt = NULL };
+ bool retried = false;
+ int error;
+
+ nd->flags &= ~LOOKUP_PARENT;
+ nd->flags |= op->intent;
+
+ if (nd->last_type != LAST_NORM) {
+ error = handle_dots(nd, nd->last_type);
+ if (error)
+ return error;
+ goto finish_open;
+ }
+
+ if (!(open_flag & O_CREAT)) {
+ if (nd->last.name[nd->last.len])
+ nd->flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
+ if (open_flag & O_PATH && !(nd->flags & LOOKUP_FOLLOW))
+ symlink_ok = true;
+ /* we _can_ be in RCU mode here */
+ error = lookup_fast(nd, path, &inode);
+ if (likely(!error))
+ goto finish_lookup;
+
+ if (error < 0)
+ goto out;
+
+ BUG_ON(nd->inode != dir->d_inode);
+ } else {
+ /* create side of things */
+ /*
+ * This will *only* deal with leaving RCU mode - LOOKUP_JUMPED
+ * has been cleared when we got to the last component we are
+ * about to look up
+ */
+ error = complete_walk(nd);
+ if (error)
+ return error;
+
+ audit_inode(name, dir, LOOKUP_PARENT);
+ error = -EISDIR;
+ /* trailing slashes? */
+ if (nd->last.name[nd->last.len])
+ goto out;
+ }
+
+retry_lookup:
+ if (op->open_flag & (O_CREAT | O_TRUNC | O_WRONLY | O_RDWR)) {
+ error = mnt_want_write(nd->path.mnt);
+ if (!error)
+ got_write = true;
+ /*
+ * do _not_ fail yet - we might not need that or fail with
+ * a different error; let lookup_open() decide; we'll be
+ * dropping this one anyway.
+ */
+ }
+ mutex_lock(&dir->d_inode->i_mutex);
+ error = lookup_open(nd, path, file, op, got_write, opened);
+ mutex_unlock(&dir->d_inode->i_mutex);
+
+ if (error <= 0) {
+ if (error)
+ goto out;
+
+ if ((*opened & FILE_CREATED) ||
+ !S_ISREG(file_inode(file)->i_mode))
+ will_truncate = false;
+
+ audit_inode(name, file->f_path.dentry, 0);
+ goto opened;
+ }
+
+ if (*opened & FILE_CREATED) {
+ /* Don't check for write permission, don't truncate */
+ open_flag &= ~O_TRUNC;
+ will_truncate = false;
+ acc_mode = MAY_OPEN;
+ path_to_nameidata(path, nd);
+ goto finish_open_created;
+ }
+
+ /*
+ * create/update audit record if it already exists.
+ */
+ if (d_is_positive(path->dentry))
+ audit_inode(name, path->dentry, 0);
+
+ /*
+ * If atomic_open() acquired write access it is dropped now due to
+ * possible mount and symlink following (this might be optimized away if
+ * necessary...)
+ */
+ if (got_write) {
+ mnt_drop_write(nd->path.mnt);
+ got_write = false;
+ }
+
+ error = -EEXIST;
+ if ((open_flag & (O_EXCL | O_CREAT)) == (O_EXCL | O_CREAT))
+ goto exit_dput;
+
+ error = follow_managed(path, nd->flags);
+ if (error < 0)
+ goto exit_dput;
+
+ if (error)
+ nd->flags |= LOOKUP_JUMPED;
+
+ BUG_ON(nd->flags & LOOKUP_RCU);
+ inode = path->dentry->d_inode;
+ error = -ENOENT;
+ if (d_is_negative(path->dentry)) {
+ path_to_nameidata(path, nd);
+ goto out;
+ }
+finish_lookup:
+ /* we _can_ be in RCU mode here */
+ if (should_follow_link(path->dentry, !symlink_ok)) {
+ if (nd->flags & LOOKUP_RCU) {
+ if (unlikely(nd->path.mnt != path->mnt ||
+ unlazy_walk(nd, path->dentry))) {
+ error = -ECHILD;
+ goto out;
+ }
+ }
+ BUG_ON(inode != path->dentry->d_inode);
+ return 1;
+ }
+
+ if ((nd->flags & LOOKUP_RCU) || nd->path.mnt != path->mnt) {
+ path_to_nameidata(path, nd);
+ } else {
+ save_parent.dentry = nd->path.dentry;
+ save_parent.mnt = mntget(path->mnt);
+ nd->path.dentry = path->dentry;
+
+ }
+ nd->inode = inode;
+ /* Why this, you ask? _Now_ we might have grown LOOKUP_JUMPED... */
+finish_open:
+ error = complete_walk(nd);
+ if (error) {
+ path_put(&save_parent);
+ return error;
+ }
+ audit_inode(name, nd->path.dentry, 0);
+ error = -EISDIR;
+ if ((open_flag & O_CREAT) && d_is_dir(nd->path.dentry))
+ goto out;
+ error = -ENOTDIR;
+ if ((nd->flags & LOOKUP_DIRECTORY) && !d_can_lookup(nd->path.dentry))
+ goto out;
+ if (!d_is_reg(nd->path.dentry))
+ will_truncate = false;
+
+ if (will_truncate) {
+ error = mnt_want_write(nd->path.mnt);
+ if (error)
+ goto out;
+ got_write = true;
+ }
+finish_open_created:
+ error = may_open(&nd->path, acc_mode, open_flag);
+ if (error)
+ goto out;
+
+ BUG_ON(*opened & FILE_OPENED); /* once it's opened, it's opened */
+ error = vfs_open(&nd->path, file, current_cred());
+ if (!error) {
+ *opened |= FILE_OPENED;
+ } else {
+ if (error == -EOPENSTALE)
+ goto stale_open;
+ goto out;
+ }
+opened:
+ error = open_check_o_direct(file);
+ if (error)
+ goto exit_fput;
+ error = ima_file_check(file, op->acc_mode, *opened);
+ if (error)
+ goto exit_fput;
+
+ if (will_truncate) {
+ error = handle_truncate(file);
+ if (error)
+ goto exit_fput;
+ }
+out:
+ if (got_write)
+ mnt_drop_write(nd->path.mnt);
+ path_put(&save_parent);
+ terminate_walk(nd);
+ return error;
+
+exit_dput:
+ path_put_conditional(path, nd);
+ goto out;
+exit_fput:
+ fput(file);
+ goto out;
+
+stale_open:
+ /* If no saved parent or already retried then can't retry */
+ if (!save_parent.dentry || retried)
+ goto out;
+
+ BUG_ON(save_parent.dentry != dir);
+ path_put(&nd->path);
+ nd->path = save_parent;
+ nd->inode = dir->d_inode;
+ save_parent.mnt = NULL;
+ save_parent.dentry = NULL;
+ if (got_write) {
+ mnt_drop_write(nd->path.mnt);
+ got_write = false;
+ }
+ retried = true;
+ goto retry_lookup;
+}
+
+static int do_tmpfile(int dfd, struct filename *pathname,
+ struct nameidata *nd, int flags,
+ const struct open_flags *op,
+ struct file *file, int *opened)
+{
+ static const struct qstr name = QSTR_INIT("/", 1);
+ struct dentry *dentry, *child;
+ struct inode *dir;
+ int error = path_lookupat(dfd, pathname,
+ flags | LOOKUP_DIRECTORY, nd);
+ if (unlikely(error))
+ return error;
+ error = mnt_want_write(nd->path.mnt);
+ if (unlikely(error))
+ goto out;
+ /* we want directory to be writable */
+ error = inode_permission(nd->inode, MAY_WRITE | MAY_EXEC);
+ if (error)
+ goto out2;
+ dentry = nd->path.dentry;
+ dir = dentry->d_inode;
+ if (!dir->i_op->tmpfile) {
+ error = -EOPNOTSUPP;
+ goto out2;
+ }
+ child = d_alloc(dentry, &name);
+ if (unlikely(!child)) {
+ error = -ENOMEM;
+ goto out2;
+ }
+ nd->flags &= ~LOOKUP_DIRECTORY;
+ nd->flags |= op->intent;
+ dput(nd->path.dentry);
+ nd->path.dentry = child;
+ error = dir->i_op->tmpfile(dir, nd->path.dentry, op->mode);
+ if (error)
+ goto out2;
+ audit_inode(pathname, nd->path.dentry, 0);
+ /* Don't check for other permissions, the inode was just created */
+ error = may_open(&nd->path, MAY_OPEN, op->open_flag);
+ if (error)
+ goto out2;
+ file->f_path.mnt = nd->path.mnt;
+ error = finish_open(file, nd->path.dentry, NULL, opened);
+ if (error)
+ goto out2;
+ error = open_check_o_direct(file);
+ if (error) {
+ fput(file);
+ } else if (!(op->open_flag & O_EXCL)) {
+ struct inode *inode = file_inode(file);
+ spin_lock(&inode->i_lock);
+ inode->i_state |= I_LINKABLE;
+ spin_unlock(&inode->i_lock);
+ }
+out2:
+ mnt_drop_write(nd->path.mnt);
+out:
+ path_put(&nd->path);
+ return error;
+}
+
+static struct file *path_openat(int dfd, struct filename *pathname,
+ struct nameidata *nd, const struct open_flags *op, int flags)
+{
+ struct file *file;
+ struct path path;
+ int opened = 0;
+ int error;
+
+ file = get_empty_filp();
+ if (IS_ERR(file))
+ return file;
+
+ file->f_flags = op->open_flag;
+
+ if (unlikely(file->f_flags & __O_TMPFILE)) {
+ error = do_tmpfile(dfd, pathname, nd, flags, op, file, &opened);
+ goto out2;
+ }
+
+ error = path_init(dfd, pathname, flags, nd);
+ if (unlikely(error))
+ goto out;
+
+ error = do_last(nd, &path, file, op, &opened, pathname);
+ while (unlikely(error > 0)) { /* trailing symlink */
+ struct path link = path;
+ void *cookie;
+ if (!(nd->flags & LOOKUP_FOLLOW)) {
+ path_put_conditional(&path, nd);
+ path_put(&nd->path);
+ error = -ELOOP;
+ break;
+ }
+ error = may_follow_link(&link, nd);
+ if (unlikely(error))
+ break;
+ nd->flags |= LOOKUP_PARENT;
+ nd->flags &= ~(LOOKUP_OPEN|LOOKUP_CREATE|LOOKUP_EXCL);
+ error = follow_link(&link, nd, &cookie);
+ if (unlikely(error))
+ break;
+ error = do_last(nd, &path, file, op, &opened, pathname);
+ put_link(nd, &link, cookie);
+ }
+out:
+ path_cleanup(nd);
+out2:
+ if (!(opened & FILE_OPENED)) {
+ BUG_ON(!error);
+ put_filp(file);
+ }
+ if (unlikely(error)) {
+ if (error == -EOPENSTALE) {
+ if (flags & LOOKUP_RCU)
+ error = -ECHILD;
+ else
+ error = -ESTALE;
+ }
+ file = ERR_PTR(error);
+ }
+ return file;
+}
+
+struct file *do_filp_open(int dfd, struct filename *pathname,
+ const struct open_flags *op)
+{
+ struct nameidata nd;
+ int flags = op->lookup_flags;
+ struct file *filp;
+
+ filp = path_openat(dfd, pathname, &nd, op, flags | LOOKUP_RCU);
+ if (unlikely(filp == ERR_PTR(-ECHILD)))
+ filp = path_openat(dfd, pathname, &nd, op, flags);
+ if (unlikely(filp == ERR_PTR(-ESTALE)))
+ filp = path_openat(dfd, pathname, &nd, op, flags | LOOKUP_REVAL);
+ return filp;
+}
+
+struct file *do_file_open_root(struct dentry *dentry, struct vfsmount *mnt,
+ const char *name, const struct open_flags *op)
+{
+ struct nameidata nd;
+ struct file *file;
+ struct filename *filename;
+ int flags = op->lookup_flags | LOOKUP_ROOT;
+
+ nd.root.mnt = mnt;
+ nd.root.dentry = dentry;
+
+ if (d_is_symlink(dentry) && op->intent & LOOKUP_OPEN)
+ return ERR_PTR(-ELOOP);
+
+ filename = getname_kernel(name);
+ if (unlikely(IS_ERR(filename)))
+ return ERR_CAST(filename);
+
+ file = path_openat(-1, filename, &nd, op, flags | LOOKUP_RCU);
+ if (unlikely(file == ERR_PTR(-ECHILD)))
+ file = path_openat(-1, filename, &nd, op, flags);
+ if (unlikely(file == ERR_PTR(-ESTALE)))
+ file = path_openat(-1, filename, &nd, op, flags | LOOKUP_REVAL);
+ putname(filename);
+ return file;
+}
+
+static struct dentry *filename_create(int dfd, struct filename *name,
+ struct path *path, unsigned int lookup_flags)
+{
+ struct dentry *dentry = ERR_PTR(-EEXIST);
+ struct nameidata nd;
+ int err2;
+ int error;
+ bool is_dir = (lookup_flags & LOOKUP_DIRECTORY);
+
+ /*
+ * Note that only LOOKUP_REVAL and LOOKUP_DIRECTORY matter here. Any
+ * other flags passed in are ignored!
+ */
+ lookup_flags &= LOOKUP_REVAL;
+
+ error = filename_lookup(dfd, name, LOOKUP_PARENT|lookup_flags, &nd);
+ if (error)
+ return ERR_PTR(error);
+
+ /*
+ * Yucky last component or no last component at all?
+ * (foo/., foo/.., /////)
+ */
+ if (nd.last_type != LAST_NORM)
+ goto out;
+ nd.flags &= ~LOOKUP_PARENT;
+ nd.flags |= LOOKUP_CREATE | LOOKUP_EXCL;
+
+ /* don't fail immediately if it's r/o, at least try to report other errors */
+ err2 = mnt_want_write(nd.path.mnt);
+ /*
+ * Do the final lookup.
+ */
+ mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
+ dentry = lookup_hash(&nd);
+ if (IS_ERR(dentry))
+ goto unlock;
+
+ error = -EEXIST;
+ if (d_is_positive(dentry))
+ goto fail;
+
+ /*
+ * Special case - lookup gave negative, but... we had foo/bar/
+ * From the vfs_mknod() POV we just have a negative dentry -
+ * all is fine. Let's be bastards - you had / on the end, you've
+ * been asking for (non-existent) directory. -ENOENT for you.
+ */
+ if (unlikely(!is_dir && nd.last.name[nd.last.len])) {
+ error = -ENOENT;
+ goto fail;
+ }
+ if (unlikely(err2)) {
+ error = err2;
+ goto fail;
+ }
+ *path = nd.path;
+ return dentry;
+fail:
+ dput(dentry);
+ dentry = ERR_PTR(error);
+unlock:
+ mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
+ if (!err2)
+ mnt_drop_write(nd.path.mnt);
+out:
+ path_put(&nd.path);
+ return dentry;
+}
+
+struct dentry *kern_path_create(int dfd, const char *pathname,
+ struct path *path, unsigned int lookup_flags)
+{
+ struct filename *filename = getname_kernel(pathname);
+ struct dentry *res;
+
+ if (IS_ERR(filename))
+ return ERR_CAST(filename);
+ res = filename_create(dfd, filename, path, lookup_flags);
+ putname(filename);
+ return res;
+}
+EXPORT_SYMBOL(kern_path_create);
+
+void done_path_create(struct path *path, struct dentry *dentry)
+{
+ dput(dentry);
+ mutex_unlock(&path->dentry->d_inode->i_mutex);
+ mnt_drop_write(path->mnt);
+ path_put(path);
+}
+EXPORT_SYMBOL(done_path_create);
+
+struct dentry *user_path_create(int dfd, const char __user *pathname,
+ struct path *path, unsigned int lookup_flags)
+{
+ struct filename *tmp = getname(pathname);
+ struct dentry *res;
+ if (IS_ERR(tmp))
+ return ERR_CAST(tmp);
+ res = filename_create(dfd, tmp, path, lookup_flags);
+ putname(tmp);
+ return res;
+}
+EXPORT_SYMBOL(user_path_create);
+
+int vfs_mknod(struct inode *dir, struct dentry *dentry, umode_t mode, dev_t dev)
+{
+ int error = may_create(dir, dentry);
+
+ if (error)
+ return error;
+
+ if ((S_ISCHR(mode) || S_ISBLK(mode)) && !capable(CAP_MKNOD))
+ return -EPERM;
+
+ if (!dir->i_op->mknod)
+ return -EPERM;
+
+ error = devcgroup_inode_mknod(mode, dev);
+ if (error)
+ return error;
+
+ error = security_inode_mknod(dir, dentry, mode, dev);
+ if (error)
+ return error;
+
+ error = dir->i_op->mknod(dir, dentry, mode, dev);
+ if (!error)
+ fsnotify_create(dir, dentry);
+ return error;
+}
+EXPORT_SYMBOL(vfs_mknod);
+
+static int may_mknod(umode_t mode)
+{
+ switch (mode & S_IFMT) {
+ case S_IFREG:
+ case S_IFCHR:
+ case S_IFBLK:
+ case S_IFIFO:
+ case S_IFSOCK:
+ case 0: /* zero mode translates to S_IFREG */
+ return 0;
+ case S_IFDIR:
+ return -EPERM;
+ default:
+ return -EINVAL;
+ }
+}
+
+SYSCALL_DEFINE4(mknodat, int, dfd, const char __user *, filename, umode_t, mode,
+ unsigned, dev)
+{
+ struct dentry *dentry;
+ struct path path;
+ int error;
+ unsigned int lookup_flags = 0;
+
+ error = may_mknod(mode);
+ if (error)
+ return error;
+retry:
+ dentry = user_path_create(dfd, filename, &path, lookup_flags);
+ if (IS_ERR(dentry))
+ return PTR_ERR(dentry);
+
+ if (!IS_POSIXACL(path.dentry->d_inode))
+ mode &= ~current_umask();
+ error = security_path_mknod(&path, dentry, mode, dev);
+ if (error)
+ goto out;
+ switch (mode & S_IFMT) {
+ case 0: case S_IFREG:
+ error = vfs_create(path.dentry->d_inode,dentry,mode,true);
+ break;
+ case S_IFCHR: case S_IFBLK:
+ error = vfs_mknod(path.dentry->d_inode,dentry,mode,
+ new_decode_dev(dev));
+ break;
+ case S_IFIFO: case S_IFSOCK:
+ error = vfs_mknod(path.dentry->d_inode,dentry,mode,0);
+ break;
+ }
+out:
+ done_path_create(&path, dentry);
+ if (retry_estale(error, lookup_flags)) {
+ lookup_flags |= LOOKUP_REVAL;
+ goto retry;
+ }
+ return error;
+}
+
+SYSCALL_DEFINE3(mknod, const char __user *, filename, umode_t, mode, unsigned, dev)
+{
+ return sys_mknodat(AT_FDCWD, filename, mode, dev);
+}
+
+int vfs_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
+{
+ int error = may_create(dir, dentry);
+ unsigned max_links = dir->i_sb->s_max_links;
+
+ if (error)
+ return error;
+
+ if (!dir->i_op->mkdir)
+ return -EPERM;
+
+ mode &= (S_IRWXUGO|S_ISVTX);
+ error = security_inode_mkdir(dir, dentry, mode);
+ if (error)
+ return error;
+
+ if (max_links && dir->i_nlink >= max_links)
+ return -EMLINK;
+
+ error = dir->i_op->mkdir(dir, dentry, mode);
+ if (!error)
+ fsnotify_mkdir(dir, dentry);
+ return error;
+}
+EXPORT_SYMBOL(vfs_mkdir);
+
+SYSCALL_DEFINE3(mkdirat, int, dfd, const char __user *, pathname, umode_t, mode)
+{
+ struct dentry *dentry;
+ struct path path;
+ int error;
+ unsigned int lookup_flags = LOOKUP_DIRECTORY;
+
+retry:
+ dentry = user_path_create(dfd, pathname, &path, lookup_flags);
+ if (IS_ERR(dentry))
+ return PTR_ERR(dentry);
+
+ if (!IS_POSIXACL(path.dentry->d_inode))
+ mode &= ~current_umask();
+ error = security_path_mkdir(&path, dentry, mode);
+ if (!error)
+ error = vfs_mkdir(path.dentry->d_inode, dentry, mode);
+ done_path_create(&path, dentry);
+ if (retry_estale(error, lookup_flags)) {
+ lookup_flags |= LOOKUP_REVAL;
+ goto retry;
+ }
+ return error;
+}
+
+SYSCALL_DEFINE2(mkdir, const char __user *, pathname, umode_t, mode)
+{
+ return sys_mkdirat(AT_FDCWD, pathname, mode);
+}
+
+/*
+ * The dentry_unhash() helper will try to drop the dentry early: we
+ * should have a usage count of 1 if we're the only user of this
+ * dentry, and if that is true (possibly after pruning the dcache),
+ * then we drop the dentry now.
+ *
+ * A low-level filesystem can, if it choses, legally
+ * do a
+ *
+ * if (!d_unhashed(dentry))
+ * return -EBUSY;
+ *
+ * if it cannot handle the case of removing a directory
+ * that is still in use by something else..
+ */
+void dentry_unhash(struct dentry *dentry)
+{
+ shrink_dcache_parent(dentry);
+ spin_lock(&dentry->d_lock);
+ if (dentry->d_lockref.count == 1)
+ __d_drop(dentry);
+ spin_unlock(&dentry->d_lock);
+}
+EXPORT_SYMBOL(dentry_unhash);
+
+int vfs_rmdir(struct inode *dir, struct dentry *dentry)
+{
+ int error = may_delete(dir, dentry, 1);
+
+ if (error)
+ return error;
+
+ if (!dir->i_op->rmdir)
+ return -EPERM;
+
+ dget(dentry);
+ mutex_lock(&dentry->d_inode->i_mutex);
+
+ error = -EBUSY;
+ if (is_local_mountpoint(dentry))
+ goto out;
+
+ error = security_inode_rmdir(dir, dentry);
+ if (error)
+ goto out;
+
+ shrink_dcache_parent(dentry);
+ error = dir->i_op->rmdir(dir, dentry);
+ if (error)
+ goto out;
+
+ dentry->d_inode->i_flags |= S_DEAD;
+ dont_mount(dentry);
+ detach_mounts(dentry);
+
+out:
+ mutex_unlock(&dentry->d_inode->i_mutex);
+ dput(dentry);
+ if (!error)
+ d_delete(dentry);
+ return error;
+}
+EXPORT_SYMBOL(vfs_rmdir);
+
+static long do_rmdir(int dfd, const char __user *pathname)
+{
+ int error = 0;
+ struct filename *name;
+ struct dentry *dentry;
+ struct nameidata nd;
+ unsigned int lookup_flags = 0;
+retry:
+ name = user_path_parent(dfd, pathname, &nd, lookup_flags);
+ if (IS_ERR(name))
+ return PTR_ERR(name);
+
+ switch(nd.last_type) {
+ case LAST_DOTDOT:
+ error = -ENOTEMPTY;
+ goto exit1;
+ case LAST_DOT:
+ error = -EINVAL;
+ goto exit1;
+ case LAST_ROOT:
+ error = -EBUSY;
+ goto exit1;
+ }
+
+ nd.flags &= ~LOOKUP_PARENT;
+ error = mnt_want_write(nd.path.mnt);
+ if (error)
+ goto exit1;
+
+ mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
+ dentry = lookup_hash(&nd);
+ error = PTR_ERR(dentry);
+ if (IS_ERR(dentry))
+ goto exit2;
+ if (!dentry->d_inode) {
+ error = -ENOENT;
+ goto exit3;
+ }
+ error = security_path_rmdir(&nd.path, dentry);
+ if (error)
+ goto exit3;
+ error = vfs_rmdir(nd.path.dentry->d_inode, dentry);
+exit3:
+ dput(dentry);
+exit2:
+ mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
+ mnt_drop_write(nd.path.mnt);
+exit1:
+ path_put(&nd.path);
+ putname(name);
+ if (retry_estale(error, lookup_flags)) {
+ lookup_flags |= LOOKUP_REVAL;
+ goto retry;
+ }
+ return error;
+}
+
+SYSCALL_DEFINE1(rmdir, const char __user *, pathname)
+{
+ return do_rmdir(AT_FDCWD, pathname);
+}
+
+/**
+ * vfs_unlink - unlink a filesystem object
+ * @dir: parent directory
+ * @dentry: victim
+ * @delegated_inode: returns victim inode, if the inode is delegated.
+ *
+ * The caller must hold dir->i_mutex.
+ *
+ * If vfs_unlink discovers a delegation, it will return -EWOULDBLOCK and
+ * return a reference to the inode in delegated_inode. The caller
+ * should then break the delegation on that inode and retry. Because
+ * breaking a delegation may take a long time, the caller should drop
+ * dir->i_mutex before doing so.
+ *
+ * Alternatively, a caller may pass NULL for delegated_inode. This may
+ * be appropriate for callers that expect the underlying filesystem not
+ * to be NFS exported.
+ */
+int vfs_unlink(struct inode *dir, struct dentry *dentry, struct inode **delegated_inode)
+{
+ struct inode *target = dentry->d_inode;
+ int error = may_delete(dir, dentry, 0);
+
+ if (error)
+ return error;
+
+ if (!dir->i_op->unlink)
+ return -EPERM;
+
+ mutex_lock(&target->i_mutex);
+ if (is_local_mountpoint(dentry))
+ error = -EBUSY;
+ else {
+ error = security_inode_unlink(dir, dentry);
+ if (!error) {
+ error = try_break_deleg(target, delegated_inode);
+ if (error)
+ goto out;
+ error = dir->i_op->unlink(dir, dentry);
+ if (!error) {
+ dont_mount(dentry);
+ detach_mounts(dentry);
+ }
+ }
+ }
+out:
+ mutex_unlock(&target->i_mutex);
+
+ /* We don't d_delete() NFS sillyrenamed files--they still exist. */
+ if (!error && !(dentry->d_flags & DCACHE_NFSFS_RENAMED)) {
+ fsnotify_link_count(target);
+ d_delete(dentry);
+ }
+
+ return error;
+}
+EXPORT_SYMBOL(vfs_unlink);
+
+/*
+ * Make sure that the actual truncation of the file will occur outside its
+ * directory's i_mutex. Truncate can take a long time if there is a lot of
+ * writeout happening, and we don't want to prevent access to the directory
+ * while waiting on the I/O.
+ */
+static long do_unlinkat(int dfd, const char __user *pathname)
+{
+ int error;
+ struct filename *name;
+ struct dentry *dentry;
+ struct nameidata nd;
+ struct inode *inode = NULL;
+ struct inode *delegated_inode = NULL;
+ unsigned int lookup_flags = 0;
+retry:
+ name = user_path_parent(dfd, pathname, &nd, lookup_flags);
+ if (IS_ERR(name))
+ return PTR_ERR(name);
+
+ error = -EISDIR;
+ if (nd.last_type != LAST_NORM)
+ goto exit1;
+
+ nd.flags &= ~LOOKUP_PARENT;
+ error = mnt_want_write(nd.path.mnt);
+ if (error)
+ goto exit1;
+retry_deleg:
+ mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
+ dentry = lookup_hash(&nd);
+ error = PTR_ERR(dentry);
+ if (!IS_ERR(dentry)) {
+ /* Why not before? Because we want correct error value */
+ if (nd.last.name[nd.last.len])
+ goto slashes;
+ inode = dentry->d_inode;
+ if (d_is_negative(dentry))
+ goto slashes;
+ ihold(inode);
+ error = security_path_unlink(&nd.path, dentry);
+ if (error)
+ goto exit2;
+ error = vfs_unlink(nd.path.dentry->d_inode, dentry, &delegated_inode);
+exit2:
+ dput(dentry);
+ }
+ mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
+ if (inode)
+ iput(inode); /* truncate the inode here */
+ inode = NULL;
+ if (delegated_inode) {
+ error = break_deleg_wait(&delegated_inode);
+ if (!error)
+ goto retry_deleg;
+ }
+ mnt_drop_write(nd.path.mnt);
+exit1:
+ path_put(&nd.path);
+ putname(name);
+ if (retry_estale(error, lookup_flags)) {
+ lookup_flags |= LOOKUP_REVAL;
+ inode = NULL;
+ goto retry;
+ }
+ return error;
+
+slashes:
+ if (d_is_negative(dentry))
+ error = -ENOENT;
+ else if (d_is_dir(dentry))
+ error = -EISDIR;
+ else
+ error = -ENOTDIR;
+ goto exit2;
+}
+
+SYSCALL_DEFINE3(unlinkat, int, dfd, const char __user *, pathname, int, flag)
+{
+ if ((flag & ~AT_REMOVEDIR) != 0)
+ return -EINVAL;
+
+ if (flag & AT_REMOVEDIR)
+ return do_rmdir(dfd, pathname);
+
+ return do_unlinkat(dfd, pathname);
+}
+
+SYSCALL_DEFINE1(unlink, const char __user *, pathname)
+{
+ return do_unlinkat(AT_FDCWD, pathname);
+}
+
+int vfs_symlink(struct inode *dir, struct dentry *dentry, const char *oldname)
+{
+ int error = may_create(dir, dentry);
+
+ if (error)
+ return error;
+
+ if (!dir->i_op->symlink)
+ return -EPERM;
+
+ error = security_inode_symlink(dir, dentry, oldname);
+ if (error)
+ return error;
+
+ error = dir->i_op->symlink(dir, dentry, oldname);
+ if (!error)
+ fsnotify_create(dir, dentry);
+ return error;
+}
+EXPORT_SYMBOL(vfs_symlink);
+
+SYSCALL_DEFINE3(symlinkat, const char __user *, oldname,
+ int, newdfd, const char __user *, newname)
+{
+ int error;
+ struct filename *from;
+ struct dentry *dentry;
+ struct path path;
+ unsigned int lookup_flags = 0;
+
+ from = getname(oldname);
+ if (IS_ERR(from))
+ return PTR_ERR(from);
+retry:
+ dentry = user_path_create(newdfd, newname, &path, lookup_flags);
+ error = PTR_ERR(dentry);
+ if (IS_ERR(dentry))
+ goto out_putname;
+
+ error = security_path_symlink(&path, dentry, from->name);
+ if (!error)
+ error = vfs_symlink(path.dentry->d_inode, dentry, from->name);
+ done_path_create(&path, dentry);
+ if (retry_estale(error, lookup_flags)) {
+ lookup_flags |= LOOKUP_REVAL;
+ goto retry;
+ }
+out_putname:
+ putname(from);
+ return error;
+}
+
+SYSCALL_DEFINE2(symlink, const char __user *, oldname, const char __user *, newname)
+{
+ return sys_symlinkat(oldname, AT_FDCWD, newname);
+}
+
+/**
+ * vfs_link - create a new link
+ * @old_dentry: object to be linked
+ * @dir: new parent
+ * @new_dentry: where to create the new link
+ * @delegated_inode: returns inode needing a delegation break
+ *
+ * The caller must hold dir->i_mutex
+ *
+ * If vfs_link discovers a delegation on the to-be-linked file in need
+ * of breaking, it will return -EWOULDBLOCK and return a reference to the
+ * inode in delegated_inode. The caller should then break the delegation
+ * and retry. Because breaking a delegation may take a long time, the
+ * caller should drop the i_mutex before doing so.
+ *
+ * Alternatively, a caller may pass NULL for delegated_inode. This may
+ * be appropriate for callers that expect the underlying filesystem not
+ * to be NFS exported.
+ */
+int vfs_link(struct dentry *old_dentry, struct inode *dir, struct dentry *new_dentry, struct inode **delegated_inode)
+{
+ struct inode *inode = old_dentry->d_inode;
+ unsigned max_links = dir->i_sb->s_max_links;
+ int error;
+
+ if (!inode)
+ return -ENOENT;
+
+ error = may_create(dir, new_dentry);
+ if (error)
+ return error;
+
+ if (dir->i_sb != inode->i_sb)
+ return -EXDEV;
+
+ /*
+ * A link to an append-only or immutable file cannot be created.
+ */
+ if (IS_APPEND(inode) || IS_IMMUTABLE(inode))
+ return -EPERM;
+ if (!dir->i_op->link)
+ return -EPERM;
+ if (S_ISDIR(inode->i_mode))
+ return -EPERM;
+
+ error = security_inode_link(old_dentry, dir, new_dentry);
+ if (error)
+ return error;
+
+ mutex_lock(&inode->i_mutex);
+ /* Make sure we don't allow creating hardlink to an unlinked file */
+ if (inode->i_nlink == 0 && !(inode->i_state & I_LINKABLE))
+ error = -ENOENT;
+ else if (max_links && inode->i_nlink >= max_links)
+ error = -EMLINK;
+ else {
+ error = try_break_deleg(inode, delegated_inode);
+ if (!error)
+ error = dir->i_op->link(old_dentry, dir, new_dentry);
+ }
+
+ if (!error && (inode->i_state & I_LINKABLE)) {
+ spin_lock(&inode->i_lock);
+ inode->i_state &= ~I_LINKABLE;
+ spin_unlock(&inode->i_lock);
+ }
+ mutex_unlock(&inode->i_mutex);
+ if (!error)
+ fsnotify_link(dir, inode, new_dentry);
+ return error;
+}
+EXPORT_SYMBOL(vfs_link);
+
+/*
+ * Hardlinks are often used in delicate situations. We avoid
+ * security-related surprises by not following symlinks on the
+ * newname. --KAB
+ *
+ * We don't follow them on the oldname either to be compatible
+ * with linux 2.0, and to avoid hard-linking to directories
+ * and other special files. --ADM
+ */
+SYSCALL_DEFINE5(linkat, int, olddfd, const char __user *, oldname,
+ int, newdfd, const char __user *, newname, int, flags)
+{
+ struct dentry *new_dentry;
+ struct path old_path, new_path;
+ struct inode *delegated_inode = NULL;
+ int how = 0;
+ int error;
+
+ if ((flags & ~(AT_SYMLINK_FOLLOW | AT_EMPTY_PATH)) != 0)
+ return -EINVAL;
+ /*
+ * To use null names we require CAP_DAC_READ_SEARCH
+ * This ensures that not everyone will be able to create
+ * handlink using the passed filedescriptor.
+ */
+ if (flags & AT_EMPTY_PATH) {
+ if (!capable(CAP_DAC_READ_SEARCH))
+ return -ENOENT;
+ how = LOOKUP_EMPTY;
+ }
+
+ if (flags & AT_SYMLINK_FOLLOW)
+ how |= LOOKUP_FOLLOW;
+retry:
+ error = user_path_at(olddfd, oldname, how, &old_path);
+ if (error)
+ return error;
+
+ new_dentry = user_path_create(newdfd, newname, &new_path,
+ (how & LOOKUP_REVAL));
+ error = PTR_ERR(new_dentry);
+ if (IS_ERR(new_dentry))
+ goto out;
+
+ error = -EXDEV;
+ if (old_path.mnt != new_path.mnt)
+ goto out_dput;
+ error = may_linkat(&old_path);
+ if (unlikely(error))
+ goto out_dput;
+ error = security_path_link(old_path.dentry, &new_path, new_dentry);
+ if (error)
+ goto out_dput;
+ error = vfs_link(old_path.dentry, new_path.dentry->d_inode, new_dentry, &delegated_inode);
+out_dput:
+ done_path_create(&new_path, new_dentry);
+ if (delegated_inode) {
+ error = break_deleg_wait(&delegated_inode);
+ if (!error) {
+ path_put(&old_path);
+ goto retry;
+ }
+ }
+ if (retry_estale(error, how)) {
+ path_put(&old_path);
+ how |= LOOKUP_REVAL;
+ goto retry;
+ }
+out:
+ path_put(&old_path);
+
+ return error;
+}
+
+SYSCALL_DEFINE2(link, const char __user *, oldname, const char __user *, newname)
+{
+ return sys_linkat(AT_FDCWD, oldname, AT_FDCWD, newname, 0);
+}
+
+/**
+ * vfs_rename - rename a filesystem object
+ * @old_dir: parent of source
+ * @old_dentry: source
+ * @new_dir: parent of destination
+ * @new_dentry: destination
+ * @delegated_inode: returns an inode needing a delegation break
+ * @flags: rename flags
+ *
+ * The caller must hold multiple mutexes--see lock_rename()).
+ *
+ * If vfs_rename discovers a delegation in need of breaking at either
+ * the source or destination, it will return -EWOULDBLOCK and return a
+ * reference to the inode in delegated_inode. The caller should then
+ * break the delegation and retry. Because breaking a delegation may
+ * take a long time, the caller should drop all locks before doing
+ * so.
+ *
+ * Alternatively, a caller may pass NULL for delegated_inode. This may
+ * be appropriate for callers that expect the underlying filesystem not
+ * to be NFS exported.
+ *
+ * The worst of all namespace operations - renaming directory. "Perverted"
+ * doesn't even start to describe it. Somebody in UCB had a heck of a trip...
+ * Problems:
+ * a) we can get into loop creation.
+ * b) race potential - two innocent renames can create a loop together.
+ * That's where 4.4 screws up. Current fix: serialization on
+ * sb->s_vfs_rename_mutex. We might be more accurate, but that's another
+ * story.
+ * c) we have to lock _four_ objects - parents and victim (if it exists),
+ * and source (if it is not a directory).
+ * And that - after we got ->i_mutex on parents (until then we don't know
+ * whether the target exists). Solution: try to be smart with locking
+ * order for inodes. We rely on the fact that tree topology may change
+ * only under ->s_vfs_rename_mutex _and_ that parent of the object we
+ * move will be locked. Thus we can rank directories by the tree
+ * (ancestors first) and rank all non-directories after them.
+ * That works since everybody except rename does "lock parent, lookup,
+ * lock child" and rename is under ->s_vfs_rename_mutex.
+ * HOWEVER, it relies on the assumption that any object with ->lookup()
+ * has no more than 1 dentry. If "hybrid" objects will ever appear,
+ * we'd better make sure that there's no link(2) for them.
+ * d) conversion from fhandle to dentry may come in the wrong moment - when
+ * we are removing the target. Solution: we will have to grab ->i_mutex
+ * in the fhandle_to_dentry code. [FIXME - current nfsfh.c relies on
+ * ->i_mutex on parents, which works but leads to some truly excessive
+ * locking].
+ */
+int vfs_rename(struct inode *old_dir, struct dentry *old_dentry,
+ struct inode *new_dir, struct dentry *new_dentry,
+ struct inode **delegated_inode, unsigned int flags)
+{
+ int error;
+ bool is_dir = d_is_dir(old_dentry);
+ const unsigned char *old_name;
+ struct inode *source = old_dentry->d_inode;
+ struct inode *target = new_dentry->d_inode;
+ bool new_is_dir = false;
+ unsigned max_links = new_dir->i_sb->s_max_links;
+
+ if (source == target)
+ return 0;
+
+ error = may_delete(old_dir, old_dentry, is_dir);
+ if (error)
+ return error;
+
+ if (!target) {
+ error = may_create(new_dir, new_dentry);
+ } else {
+ new_is_dir = d_is_dir(new_dentry);
+
+ if (!(flags & RENAME_EXCHANGE))
+ error = may_delete(new_dir, new_dentry, is_dir);
+ else
+ error = may_delete(new_dir, new_dentry, new_is_dir);
+ }
+ if (error)
+ return error;
+
+ if (!old_dir->i_op->rename && !old_dir->i_op->rename2)
+ return -EPERM;
+
+ if (flags && !old_dir->i_op->rename2)
+ return -EINVAL;
+
+ /*
+ * If we are going to change the parent - check write permissions,
+ * we'll need to flip '..'.
+ */
+ if (new_dir != old_dir) {
+ if (is_dir) {
+ error = inode_permission(source, MAY_WRITE);
+ if (error)
+ return error;
+ }
+ if ((flags & RENAME_EXCHANGE) && new_is_dir) {
+ error = inode_permission(target, MAY_WRITE);
+ if (error)
+ return error;
+ }
+ }
+
+ error = security_inode_rename(old_dir, old_dentry, new_dir, new_dentry,
+ flags);
+ if (error)
+ return error;
+
+ old_name = fsnotify_oldname_init(old_dentry->d_name.name);
+ dget(new_dentry);
+ if (!is_dir || (flags & RENAME_EXCHANGE))
+ lock_two_nondirectories(source, target);
+ else if (target)
+ mutex_lock(&target->i_mutex);
+
+ error = -EBUSY;
+ if (is_local_mountpoint(old_dentry) || is_local_mountpoint(new_dentry))
+ goto out;
+
+ if (max_links && new_dir != old_dir) {
+ error = -EMLINK;
+ if (is_dir && !new_is_dir && new_dir->i_nlink >= max_links)
+ goto out;
+ if ((flags & RENAME_EXCHANGE) && !is_dir && new_is_dir &&
+ old_dir->i_nlink >= max_links)
+ goto out;
+ }
+ if (is_dir && !(flags & RENAME_EXCHANGE) && target)
+ shrink_dcache_parent(new_dentry);
+ if (!is_dir) {
+ error = try_break_deleg(source, delegated_inode);
+ if (error)
+ goto out;
+ }
+ if (target && !new_is_dir) {
+ error = try_break_deleg(target, delegated_inode);
+ if (error)
+ goto out;
+ }
+ if (!old_dir->i_op->rename2) {
+ error = old_dir->i_op->rename(old_dir, old_dentry,
+ new_dir, new_dentry);
+ } else {
+ WARN_ON(old_dir->i_op->rename != NULL);
+ error = old_dir->i_op->rename2(old_dir, old_dentry,
+ new_dir, new_dentry, flags);
+ }
+ if (error)
+ goto out;
+
+ if (!(flags & RENAME_EXCHANGE) && target) {
+ if (is_dir)
+ target->i_flags |= S_DEAD;
+ dont_mount(new_dentry);
+ detach_mounts(new_dentry);
+ }
+ if (!(old_dir->i_sb->s_type->fs_flags & FS_RENAME_DOES_D_MOVE)) {
+ if (!(flags & RENAME_EXCHANGE))
+ d_move(old_dentry, new_dentry);
+ else
+ d_exchange(old_dentry, new_dentry);
+ }
+out:
+ if (!is_dir || (flags & RENAME_EXCHANGE))
+ unlock_two_nondirectories(source, target);
+ else if (target)
+ mutex_unlock(&target->i_mutex);
+ dput(new_dentry);
+ if (!error) {
+ fsnotify_move(old_dir, new_dir, old_name, is_dir,
+ !(flags & RENAME_EXCHANGE) ? target : NULL, old_dentry);
+ if (flags & RENAME_EXCHANGE) {
+ fsnotify_move(new_dir, old_dir, old_dentry->d_name.name,
+ new_is_dir, NULL, new_dentry);
+ }
+ }
+ fsnotify_oldname_free(old_name);
+
+ return error;
+}
+EXPORT_SYMBOL(vfs_rename);
+
+SYSCALL_DEFINE5(renameat2, int, olddfd, const char __user *, oldname,
+ int, newdfd, const char __user *, newname, unsigned int, flags)
+{
+ struct dentry *old_dir, *new_dir;
+ struct dentry *old_dentry, *new_dentry;
+ struct dentry *trap;
+ struct nameidata oldnd, newnd;
+ struct inode *delegated_inode = NULL;
+ struct filename *from;
+ struct filename *to;
+ unsigned int lookup_flags = 0;
+ bool should_retry = false;
+ int error;
+
+ if (flags & ~(RENAME_NOREPLACE | RENAME_EXCHANGE | RENAME_WHITEOUT))
+ return -EINVAL;
+
+ if ((flags & (RENAME_NOREPLACE | RENAME_WHITEOUT)) &&
+ (flags & RENAME_EXCHANGE))
+ return -EINVAL;
+
+ if ((flags & RENAME_WHITEOUT) && !capable(CAP_MKNOD))
+ return -EPERM;
+
+retry:
+ from = user_path_parent(olddfd, oldname, &oldnd, lookup_flags);
+ if (IS_ERR(from)) {
+ error = PTR_ERR(from);
+ goto exit;
+ }
+
+ to = user_path_parent(newdfd, newname, &newnd, lookup_flags);
+ if (IS_ERR(to)) {
+ error = PTR_ERR(to);
+ goto exit1;
+ }
+
+ error = -EXDEV;
+ if (oldnd.path.mnt != newnd.path.mnt)
+ goto exit2;
+
+ old_dir = oldnd.path.dentry;
+ error = -EBUSY;
+ if (oldnd.last_type != LAST_NORM)
+ goto exit2;
+
+ new_dir = newnd.path.dentry;
+ if (flags & RENAME_NOREPLACE)
+ error = -EEXIST;
+ if (newnd.last_type != LAST_NORM)
+ goto exit2;
+
+ error = mnt_want_write(oldnd.path.mnt);
+ if (error)
+ goto exit2;
+
+ oldnd.flags &= ~LOOKUP_PARENT;
+ newnd.flags &= ~LOOKUP_PARENT;
+ if (!(flags & RENAME_EXCHANGE))
+ newnd.flags |= LOOKUP_RENAME_TARGET;
+
+retry_deleg:
+ trap = lock_rename(new_dir, old_dir);
+
+ old_dentry = lookup_hash(&oldnd);
+ error = PTR_ERR(old_dentry);
+ if (IS_ERR(old_dentry))
+ goto exit3;
+ /* source must exist */
+ error = -ENOENT;
+ if (d_is_negative(old_dentry))
+ goto exit4;
+ new_dentry = lookup_hash(&newnd);
+ error = PTR_ERR(new_dentry);
+ if (IS_ERR(new_dentry))
+ goto exit4;
+ error = -EEXIST;
+ if ((flags & RENAME_NOREPLACE) && d_is_positive(new_dentry))
+ goto exit5;
+ if (flags & RENAME_EXCHANGE) {
+ error = -ENOENT;
+ if (d_is_negative(new_dentry))
+ goto exit5;
+
+ if (!d_is_dir(new_dentry)) {
+ error = -ENOTDIR;
+ if (newnd.last.name[newnd.last.len])
+ goto exit5;
+ }
+ }
+ /* unless the source is a directory trailing slashes give -ENOTDIR */
+ if (!d_is_dir(old_dentry)) {
+ error = -ENOTDIR;
+ if (oldnd.last.name[oldnd.last.len])
+ goto exit5;
+ if (!(flags & RENAME_EXCHANGE) && newnd.last.name[newnd.last.len])
+ goto exit5;
+ }
+ /* source should not be ancestor of target */
+ error = -EINVAL;
+ if (old_dentry == trap)
+ goto exit5;
+ /* target should not be an ancestor of source */
+ if (!(flags & RENAME_EXCHANGE))
+ error = -ENOTEMPTY;
+ if (new_dentry == trap)
+ goto exit5;
+
+ error = security_path_rename(&oldnd.path, old_dentry,
+ &newnd.path, new_dentry, flags);
+ if (error)
+ goto exit5;
+ error = vfs_rename(old_dir->d_inode, old_dentry,
+ new_dir->d_inode, new_dentry,
+ &delegated_inode, flags);
+exit5:
+ dput(new_dentry);
+exit4:
+ dput(old_dentry);
+exit3:
+ unlock_rename(new_dir, old_dir);
+ if (delegated_inode) {
+ error = break_deleg_wait(&delegated_inode);
+ if (!error)
+ goto retry_deleg;
+ }
+ mnt_drop_write(oldnd.path.mnt);
+exit2:
+ if (retry_estale(error, lookup_flags))
+ should_retry = true;
+ path_put(&newnd.path);
+ putname(to);
+exit1:
+ path_put(&oldnd.path);
+ putname(from);
+ if (should_retry) {
+ should_retry = false;
+ lookup_flags |= LOOKUP_REVAL;
+ goto retry;
+ }
+exit:
+ return error;
+}
+
+SYSCALL_DEFINE4(renameat, int, olddfd, const char __user *, oldname,
+ int, newdfd, const char __user *, newname)
+{
+ return sys_renameat2(olddfd, oldname, newdfd, newname, 0);
+}
+
+SYSCALL_DEFINE2(rename, const char __user *, oldname, const char __user *, newname)
+{
+ return sys_renameat2(AT_FDCWD, oldname, AT_FDCWD, newname, 0);
+}
+
+int vfs_whiteout(struct inode *dir, struct dentry *dentry)
+{
+ int error = may_create(dir, dentry);
+ if (error)
+ return error;
+
+ if (!dir->i_op->mknod)
+ return -EPERM;
+
+ return dir->i_op->mknod(dir, dentry,
+ S_IFCHR | WHITEOUT_MODE, WHITEOUT_DEV);
+}
+EXPORT_SYMBOL(vfs_whiteout);
+
+int readlink_copy(char __user *buffer, int buflen, const char *link)
+{
+ int len = PTR_ERR(link);
+ if (IS_ERR(link))
+ goto out;
+
+ len = strlen(link);
+ if (len > (unsigned) buflen)
+ len = buflen;
+ if (copy_to_user(buffer, link, len))
+ len = -EFAULT;
+out:
+ return len;
+}
+EXPORT_SYMBOL(readlink_copy);
+
+/*
+ * A helper for ->readlink(). This should be used *ONLY* for symlinks that
+ * have ->follow_link() touching nd only in nd_set_link(). Using (or not
+ * using) it for any given inode is up to filesystem.
+ */
+int generic_readlink(struct dentry *dentry, char __user *buffer, int buflen)
+{
+ struct nameidata nd;
+ void *cookie;
+ int res;
+
+ nd.depth = 0;
+ cookie = dentry->d_inode->i_op->follow_link(dentry, &nd);
+ if (IS_ERR(cookie))
+ return PTR_ERR(cookie);
+
+ res = readlink_copy(buffer, buflen, nd_get_link(&nd));
+ if (dentry->d_inode->i_op->put_link)
+ dentry->d_inode->i_op->put_link(dentry, &nd, cookie);
+ return res;
+}
+EXPORT_SYMBOL(generic_readlink);
+
+/* get the link contents into pagecache */
+static char *page_getlink(struct dentry * dentry, struct page **ppage)
+{
+ char *kaddr;
+ struct page *page;
+ struct address_space *mapping = dentry->d_inode->i_mapping;
+ page = read_mapping_page(mapping, 0, NULL);
+ if (IS_ERR(page))
+ return (char*)page;
+ *ppage = page;
+ kaddr = kmap(page);
+ nd_terminate_link(kaddr, dentry->d_inode->i_size, PAGE_SIZE - 1);
+ return kaddr;
+}
+
+int page_readlink(struct dentry *dentry, char __user *buffer, int buflen)
+{
+ struct page *page = NULL;
+ int res = readlink_copy(buffer, buflen, page_getlink(dentry, &page));
+ if (page) {
+ kunmap(page);
+ page_cache_release(page);
+ }
+ return res;
+}
+EXPORT_SYMBOL(page_readlink);
+
+void *page_follow_link_light(struct dentry *dentry, struct nameidata *nd)
+{
+ struct page *page = NULL;
+ nd_set_link(nd, page_getlink(dentry, &page));
+ return page;
+}
+EXPORT_SYMBOL(page_follow_link_light);
+
+void page_put_link(struct dentry *dentry, struct nameidata *nd, void *cookie)
+{
+ struct page *page = cookie;
+
+ if (page) {
+ kunmap(page);
+ page_cache_release(page);
+ }
+}
+EXPORT_SYMBOL(page_put_link);
+
+/*
+ * The nofs argument instructs pagecache_write_begin to pass AOP_FLAG_NOFS
+ */
+int __page_symlink(struct inode *inode, const char *symname, int len, int nofs)
+{
+ struct address_space *mapping = inode->i_mapping;
+ struct page *page;
+ void *fsdata;
+ int err;
+ char *kaddr;
+ unsigned int flags = AOP_FLAG_UNINTERRUPTIBLE;
+ if (nofs)
+ flags |= AOP_FLAG_NOFS;
+
+retry:
+ err = pagecache_write_begin(NULL, mapping, 0, len-1,
+ flags, &page, &fsdata);
+ if (err)
+ goto fail;
+
+ kaddr = kmap_atomic(page);
+ memcpy(kaddr, symname, len-1);
+ kunmap_atomic(kaddr);
+
+ err = pagecache_write_end(NULL, mapping, 0, len-1, len-1,
+ page, fsdata);
+ if (err < 0)
+ goto fail;
+ if (err < len-1)
+ goto retry;
+
+ mark_inode_dirty(inode);
+ return 0;
+fail:
+ return err;
+}
+EXPORT_SYMBOL(__page_symlink);
+
+int page_symlink(struct inode *inode, const char *symname, int len)
+{
+ return __page_symlink(inode, symname, len,
+ !(mapping_gfp_mask(inode->i_mapping) & __GFP_FS));
+}
+EXPORT_SYMBOL(page_symlink);
+
+const struct inode_operations page_symlink_inode_operations = {
+ .readlink = generic_readlink,
+ .follow_link = page_follow_link_light,
+ .put_link = page_put_link,
+};
+EXPORT_SYMBOL(page_symlink_inode_operations);