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-rw-r--r--src/basic/mount-util.c533
1 files changed, 533 insertions, 0 deletions
diff --git a/src/basic/mount-util.c b/src/basic/mount-util.c
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--- /dev/null
+++ b/src/basic/mount-util.c
@@ -0,0 +1,533 @@
+/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
+
+/***
+ This file is part of systemd.
+
+ Copyright 2010 Lennart Poettering
+
+ systemd is free software; you can redistribute it and/or modify it
+ under the terms of the GNU Lesser General Public License as published by
+ the Free Software Foundation; either version 2.1 of the License, or
+ (at your option) any later version.
+
+ systemd is distributed in the hope that it will be useful, but
+ WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public License
+ along with systemd; If not, see <http://www.gnu.org/licenses/>.
+***/
+
+#include <errno.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/mount.h>
+#include <sys/stat.h>
+#include <sys/statvfs.h>
+#include <unistd.h>
+
+#include "alloc-util.h"
+#include "escape.h"
+#include "fd-util.h"
+#include "fileio.h"
+#include "hashmap.h"
+#include "mount-util.h"
+#include "parse-util.h"
+#include "path-util.h"
+#include "set.h"
+#include "stdio-util.h"
+#include "string-util.h"
+
+static int fd_fdinfo_mnt_id(int fd, const char *filename, int flags, int *mnt_id) {
+ char path[strlen("/proc/self/fdinfo/") + DECIMAL_STR_MAX(int)];
+ _cleanup_free_ char *fdinfo = NULL;
+ _cleanup_close_ int subfd = -1;
+ char *p;
+ int r;
+
+ if ((flags & AT_EMPTY_PATH) && isempty(filename))
+ xsprintf(path, "/proc/self/fdinfo/%i", fd);
+ else {
+ subfd = openat(fd, filename, O_RDONLY|O_CLOEXEC|O_NOCTTY|O_PATH);
+ if (subfd < 0)
+ return -errno;
+
+ xsprintf(path, "/proc/self/fdinfo/%i", subfd);
+ }
+
+ r = read_full_file(path, &fdinfo, NULL);
+ if (r == -ENOENT) /* The fdinfo directory is a relatively new addition */
+ return -EOPNOTSUPP;
+ if (r < 0)
+ return -errno;
+
+ p = startswith(fdinfo, "mnt_id:");
+ if (!p) {
+ p = strstr(fdinfo, "\nmnt_id:");
+ if (!p) /* The mnt_id field is a relatively new addition */
+ return -EOPNOTSUPP;
+
+ p += 8;
+ }
+
+ p += strspn(p, WHITESPACE);
+ p[strcspn(p, WHITESPACE)] = 0;
+
+ return safe_atoi(p, mnt_id);
+}
+
+
+int fd_is_mount_point(int fd, const char *filename, int flags) {
+ union file_handle_union h = FILE_HANDLE_INIT, h_parent = FILE_HANDLE_INIT;
+ int mount_id = -1, mount_id_parent = -1;
+ bool nosupp = false, check_st_dev = true;
+ struct stat a, b;
+ int r;
+
+ assert(fd >= 0);
+ assert(filename);
+
+ /* First we will try the name_to_handle_at() syscall, which
+ * tells us the mount id and an opaque file "handle". It is
+ * not supported everywhere though (kernel compile-time
+ * option, not all file systems are hooked up). If it works
+ * the mount id is usually good enough to tell us whether
+ * something is a mount point.
+ *
+ * If that didn't work we will try to read the mount id from
+ * /proc/self/fdinfo/<fd>. This is almost as good as
+ * name_to_handle_at(), however, does not return the
+ * opaque file handle. The opaque file handle is pretty useful
+ * to detect the root directory, which we should always
+ * consider a mount point. Hence we use this only as
+ * fallback. Exporting the mnt_id in fdinfo is a pretty recent
+ * kernel addition.
+ *
+ * As last fallback we do traditional fstat() based st_dev
+ * comparisons. This is how things were traditionally done,
+ * but unionfs breaks breaks this since it exposes file
+ * systems with a variety of st_dev reported. Also, btrfs
+ * subvolumes have different st_dev, even though they aren't
+ * real mounts of their own. */
+
+ r = name_to_handle_at(fd, filename, &h.handle, &mount_id, flags);
+ if (r < 0) {
+ if (errno == ENOSYS)
+ /* This kernel does not support name_to_handle_at()
+ * fall back to simpler logic. */
+ goto fallback_fdinfo;
+ else if (errno == EOPNOTSUPP)
+ /* This kernel or file system does not support
+ * name_to_handle_at(), hence let's see if the
+ * upper fs supports it (in which case it is a
+ * mount point), otherwise fallback to the
+ * traditional stat() logic */
+ nosupp = true;
+ else
+ return -errno;
+ }
+
+ r = name_to_handle_at(fd, "", &h_parent.handle, &mount_id_parent, AT_EMPTY_PATH);
+ if (r < 0) {
+ if (errno == EOPNOTSUPP) {
+ if (nosupp)
+ /* Neither parent nor child do name_to_handle_at()?
+ We have no choice but to fall back. */
+ goto fallback_fdinfo;
+ else
+ /* The parent can't do name_to_handle_at() but the
+ * directory we are interested in can?
+ * If so, it must be a mount point. */
+ return 1;
+ } else
+ return -errno;
+ }
+
+ /* The parent can do name_to_handle_at() but the
+ * directory we are interested in can't? If so, it
+ * must be a mount point. */
+ if (nosupp)
+ return 1;
+
+ /* If the file handle for the directory we are
+ * interested in and its parent are identical, we
+ * assume this is the root directory, which is a mount
+ * point. */
+
+ if (h.handle.handle_bytes == h_parent.handle.handle_bytes &&
+ h.handle.handle_type == h_parent.handle.handle_type &&
+ memcmp(h.handle.f_handle, h_parent.handle.f_handle, h.handle.handle_bytes) == 0)
+ return 1;
+
+ return mount_id != mount_id_parent;
+
+fallback_fdinfo:
+ r = fd_fdinfo_mnt_id(fd, filename, flags, &mount_id);
+ if (r == -EOPNOTSUPP)
+ goto fallback_fstat;
+ if (r < 0)
+ return r;
+
+ r = fd_fdinfo_mnt_id(fd, "", AT_EMPTY_PATH, &mount_id_parent);
+ if (r < 0)
+ return r;
+
+ if (mount_id != mount_id_parent)
+ return 1;
+
+ /* Hmm, so, the mount ids are the same. This leaves one
+ * special case though for the root file system. For that,
+ * let's see if the parent directory has the same inode as we
+ * are interested in. Hence, let's also do fstat() checks now,
+ * too, but avoid the st_dev comparisons, since they aren't
+ * that useful on unionfs mounts. */
+ check_st_dev = false;
+
+fallback_fstat:
+ /* yay for fstatat() taking a different set of flags than the other
+ * _at() above */
+ if (flags & AT_SYMLINK_FOLLOW)
+ flags &= ~AT_SYMLINK_FOLLOW;
+ else
+ flags |= AT_SYMLINK_NOFOLLOW;
+ if (fstatat(fd, filename, &a, flags) < 0)
+ return -errno;
+
+ if (fstatat(fd, "", &b, AT_EMPTY_PATH) < 0)
+ return -errno;
+
+ /* A directory with same device and inode as its parent? Must
+ * be the root directory */
+ if (a.st_dev == b.st_dev &&
+ a.st_ino == b.st_ino)
+ return 1;
+
+ return check_st_dev && (a.st_dev != b.st_dev);
+}
+
+/* flags can be AT_SYMLINK_FOLLOW or 0 */
+int path_is_mount_point(const char *t, int flags) {
+ _cleanup_close_ int fd = -1;
+ _cleanup_free_ char *canonical = NULL, *parent = NULL;
+
+ assert(t);
+
+ if (path_equal(t, "/"))
+ return 1;
+
+ /* we need to resolve symlinks manually, we can't just rely on
+ * fd_is_mount_point() to do that for us; if we have a structure like
+ * /bin -> /usr/bin/ and /usr is a mount point, then the parent that we
+ * look at needs to be /usr, not /. */
+ if (flags & AT_SYMLINK_FOLLOW) {
+ canonical = canonicalize_file_name(t);
+ if (!canonical)
+ return -errno;
+
+ t = canonical;
+ }
+
+ parent = dirname_malloc(t);
+ if (!parent)
+ return -ENOMEM;
+
+ fd = openat(AT_FDCWD, parent, O_RDONLY|O_NONBLOCK|O_DIRECTORY|O_CLOEXEC|O_PATH);
+ if (fd < 0)
+ return -errno;
+
+ return fd_is_mount_point(fd, basename(t), flags);
+}
+
+int umount_recursive(const char *prefix, int flags) {
+ bool again;
+ int n = 0, r;
+
+ /* Try to umount everything recursively below a
+ * directory. Also, take care of stacked mounts, and keep
+ * unmounting them until they are gone. */
+
+ do {
+ _cleanup_fclose_ FILE *proc_self_mountinfo = NULL;
+
+ again = false;
+ r = 0;
+
+ proc_self_mountinfo = fopen("/proc/self/mountinfo", "re");
+ if (!proc_self_mountinfo)
+ return -errno;
+
+ for (;;) {
+ _cleanup_free_ char *path = NULL, *p = NULL;
+ int k;
+
+ k = fscanf(proc_self_mountinfo,
+ "%*s " /* (1) mount id */
+ "%*s " /* (2) parent id */
+ "%*s " /* (3) major:minor */
+ "%*s " /* (4) root */
+ "%ms " /* (5) mount point */
+ "%*s" /* (6) mount options */
+ "%*[^-]" /* (7) optional fields */
+ "- " /* (8) separator */
+ "%*s " /* (9) file system type */
+ "%*s" /* (10) mount source */
+ "%*s" /* (11) mount options 2 */
+ "%*[^\n]", /* some rubbish at the end */
+ &path);
+ if (k != 1) {
+ if (k == EOF)
+ break;
+
+ continue;
+ }
+
+ r = cunescape(path, UNESCAPE_RELAX, &p);
+ if (r < 0)
+ return r;
+
+ if (!path_startswith(p, prefix))
+ continue;
+
+ if (umount2(p, flags) < 0) {
+ r = -errno;
+ continue;
+ }
+
+ again = true;
+ n++;
+
+ break;
+ }
+
+ } while (again);
+
+ return r ? r : n;
+}
+
+static int get_mount_flags(const char *path, unsigned long *flags) {
+ struct statvfs buf;
+
+ if (statvfs(path, &buf) < 0)
+ return -errno;
+ *flags = buf.f_flag;
+ return 0;
+}
+
+int bind_remount_recursive(const char *prefix, bool ro) {
+ _cleanup_set_free_free_ Set *done = NULL;
+ _cleanup_free_ char *cleaned = NULL;
+ int r;
+
+ /* Recursively remount a directory (and all its submounts)
+ * read-only or read-write. If the directory is already
+ * mounted, we reuse the mount and simply mark it
+ * MS_BIND|MS_RDONLY (or remove the MS_RDONLY for read-write
+ * operation). If it isn't we first make it one. Afterwards we
+ * apply MS_BIND|MS_RDONLY (or remove MS_RDONLY) to all
+ * submounts we can access, too. When mounts are stacked on
+ * the same mount point we only care for each individual
+ * "top-level" mount on each point, as we cannot
+ * influence/access the underlying mounts anyway. We do not
+ * have any effect on future submounts that might get
+ * propagated, they migt be writable. This includes future
+ * submounts that have been triggered via autofs. */
+
+ cleaned = strdup(prefix);
+ if (!cleaned)
+ return -ENOMEM;
+
+ path_kill_slashes(cleaned);
+
+ done = set_new(&string_hash_ops);
+ if (!done)
+ return -ENOMEM;
+
+ for (;;) {
+ _cleanup_fclose_ FILE *proc_self_mountinfo = NULL;
+ _cleanup_set_free_free_ Set *todo = NULL;
+ bool top_autofs = false;
+ char *x;
+ unsigned long orig_flags;
+
+ todo = set_new(&string_hash_ops);
+ if (!todo)
+ return -ENOMEM;
+
+ proc_self_mountinfo = fopen("/proc/self/mountinfo", "re");
+ if (!proc_self_mountinfo)
+ return -errno;
+
+ for (;;) {
+ _cleanup_free_ char *path = NULL, *p = NULL, *type = NULL;
+ int k;
+
+ k = fscanf(proc_self_mountinfo,
+ "%*s " /* (1) mount id */
+ "%*s " /* (2) parent id */
+ "%*s " /* (3) major:minor */
+ "%*s " /* (4) root */
+ "%ms " /* (5) mount point */
+ "%*s" /* (6) mount options (superblock) */
+ "%*[^-]" /* (7) optional fields */
+ "- " /* (8) separator */
+ "%ms " /* (9) file system type */
+ "%*s" /* (10) mount source */
+ "%*s" /* (11) mount options (bind mount) */
+ "%*[^\n]", /* some rubbish at the end */
+ &path,
+ &type);
+ if (k != 2) {
+ if (k == EOF)
+ break;
+
+ continue;
+ }
+
+ r = cunescape(path, UNESCAPE_RELAX, &p);
+ if (r < 0)
+ return r;
+
+ /* Let's ignore autofs mounts. If they aren't
+ * triggered yet, we want to avoid triggering
+ * them, as we don't make any guarantees for
+ * future submounts anyway. If they are
+ * already triggered, then we will find
+ * another entry for this. */
+ if (streq(type, "autofs")) {
+ top_autofs = top_autofs || path_equal(cleaned, p);
+ continue;
+ }
+
+ if (path_startswith(p, cleaned) &&
+ !set_contains(done, p)) {
+
+ r = set_consume(todo, p);
+ p = NULL;
+
+ if (r == -EEXIST)
+ continue;
+ if (r < 0)
+ return r;
+ }
+ }
+
+ /* If we have no submounts to process anymore and if
+ * the root is either already done, or an autofs, we
+ * are done */
+ if (set_isempty(todo) &&
+ (top_autofs || set_contains(done, cleaned)))
+ return 0;
+
+ if (!set_contains(done, cleaned) &&
+ !set_contains(todo, cleaned)) {
+ /* The prefix directory itself is not yet a
+ * mount, make it one. */
+ if (mount(cleaned, cleaned, NULL, MS_BIND|MS_REC, NULL) < 0)
+ return -errno;
+
+ orig_flags = 0;
+ (void) get_mount_flags(cleaned, &orig_flags);
+ orig_flags &= ~MS_RDONLY;
+
+ if (mount(NULL, prefix, NULL, orig_flags|MS_BIND|MS_REMOUNT|(ro ? MS_RDONLY : 0), NULL) < 0)
+ return -errno;
+
+ x = strdup(cleaned);
+ if (!x)
+ return -ENOMEM;
+
+ r = set_consume(done, x);
+ if (r < 0)
+ return r;
+ }
+
+ while ((x = set_steal_first(todo))) {
+
+ r = set_consume(done, x);
+ if (r == -EEXIST || r == 0)
+ continue;
+ if (r < 0)
+ return r;
+
+ /* Try to reuse the original flag set, but
+ * don't care for errors, in case of
+ * obstructed mounts */
+ orig_flags = 0;
+ (void) get_mount_flags(x, &orig_flags);
+ orig_flags &= ~MS_RDONLY;
+
+ if (mount(NULL, x, NULL, orig_flags|MS_BIND|MS_REMOUNT|(ro ? MS_RDONLY : 0), NULL) < 0) {
+
+ /* Deal with mount points that are
+ * obstructed by a later mount */
+
+ if (errno != ENOENT)
+ return -errno;
+ }
+
+ }
+ }
+}
+
+int mount_move_root(const char *path) {
+ assert(path);
+
+ if (chdir(path) < 0)
+ return -errno;
+
+ if (mount(path, "/", NULL, MS_MOVE, NULL) < 0)
+ return -errno;
+
+ if (chroot(".") < 0)
+ return -errno;
+
+ if (chdir("/") < 0)
+ return -errno;
+
+ return 0;
+}
+
+bool fstype_is_network(const char *fstype) {
+ static const char table[] =
+ "afs\0"
+ "cifs\0"
+ "smbfs\0"
+ "sshfs\0"
+ "ncpfs\0"
+ "ncp\0"
+ "nfs\0"
+ "nfs4\0"
+ "gfs\0"
+ "gfs2\0"
+ "glusterfs\0";
+
+ const char *x;
+
+ x = startswith(fstype, "fuse.");
+ if (x)
+ fstype = x;
+
+ return nulstr_contains(table, fstype);
+}
+
+int repeat_unmount(const char *path, int flags) {
+ bool done = false;
+
+ assert(path);
+
+ /* If there are multiple mounts on a mount point, this
+ * removes them all */
+
+ for (;;) {
+ if (umount2(path, flags) < 0) {
+
+ if (errno == EINVAL)
+ return done;
+
+ return -errno;
+ }
+
+ done = true;
+ }
+}
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