diff options
Diffstat (limited to 'kernel/user_namespace.c')
| -rw-r--r-- | kernel/user_namespace.c | 1012 |
1 files changed, 1012 insertions, 0 deletions
diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c new file mode 100644 index 000000000..4109f8320 --- /dev/null +++ b/kernel/user_namespace.c @@ -0,0 +1,1012 @@ +/* + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public License as + * published by the Free Software Foundation, version 2 of the + * License. + */ + +#include <linux/export.h> +#include <linux/nsproxy.h> +#include <linux/slab.h> +#include <linux/user_namespace.h> +#include <linux/proc_ns.h> +#include <linux/highuid.h> +#include <linux/cred.h> +#include <linux/securebits.h> +#include <linux/keyctl.h> +#include <linux/key-type.h> +#include <keys/user-type.h> +#include <linux/seq_file.h> +#include <linux/fs.h> +#include <linux/uaccess.h> +#include <linux/ctype.h> +#include <linux/projid.h> +#include <linux/fs_struct.h> + +static struct kmem_cache *user_ns_cachep __read_mostly; +static DEFINE_MUTEX(userns_state_mutex); + +static bool new_idmap_permitted(const struct file *file, + struct user_namespace *ns, int cap_setid, + struct uid_gid_map *map); + +static void set_cred_user_ns(struct cred *cred, struct user_namespace *user_ns) +{ + /* Start with the same capabilities as init but useless for doing + * anything as the capabilities are bound to the new user namespace. + */ + cred->securebits = SECUREBITS_DEFAULT; + cred->cap_inheritable = CAP_EMPTY_SET; + cred->cap_permitted = CAP_FULL_SET; + cred->cap_effective = CAP_FULL_SET; + cred->cap_bset = CAP_FULL_SET; +#ifdef CONFIG_KEYS + key_put(cred->request_key_auth); + cred->request_key_auth = NULL; +#endif + /* tgcred will be cleared in our caller bc CLONE_THREAD won't be set */ + cred->user_ns = user_ns; +} + +/* + * Create a new user namespace, deriving the creator from the user in the + * passed credentials, and replacing that user with the new root user for the + * new namespace. + * + * This is called by copy_creds(), which will finish setting the target task's + * credentials. + */ +int create_user_ns(struct cred *new) +{ + struct user_namespace *ns, *parent_ns = new->user_ns; + kuid_t owner = new->euid; + kgid_t group = new->egid; + int ret; + + if (parent_ns->level > 32) + return -EUSERS; + + /* + * Verify that we can not violate the policy of which files + * may be accessed that is specified by the root directory, + * by verifing that the root directory is at the root of the + * mount namespace which allows all files to be accessed. + */ + if (current_chrooted()) + return -EPERM; + + /* The creator needs a mapping in the parent user namespace + * or else we won't be able to reasonably tell userspace who + * created a user_namespace. + */ + if (!kuid_has_mapping(parent_ns, owner) || + !kgid_has_mapping(parent_ns, group)) + return -EPERM; + + ns = kmem_cache_zalloc(user_ns_cachep, GFP_KERNEL); + if (!ns) + return -ENOMEM; + + ret = ns_alloc_inum(&ns->ns); + if (ret) { + kmem_cache_free(user_ns_cachep, ns); + return ret; + } + ns->ns.ops = &userns_operations; + + atomic_set(&ns->count, 1); + /* Leave the new->user_ns reference with the new user namespace. */ + ns->parent = parent_ns; + ns->level = parent_ns->level + 1; + ns->owner = owner; + ns->group = group; + + /* Inherit USERNS_SETGROUPS_ALLOWED from our parent */ + mutex_lock(&userns_state_mutex); + ns->flags = parent_ns->flags; + mutex_unlock(&userns_state_mutex); + + set_cred_user_ns(new, ns); + +#ifdef CONFIG_PERSISTENT_KEYRINGS + init_rwsem(&ns->persistent_keyring_register_sem); +#endif + return 0; +} + +int unshare_userns(unsigned long unshare_flags, struct cred **new_cred) +{ + struct cred *cred; + int err = -ENOMEM; + + if (!(unshare_flags & CLONE_NEWUSER)) + return 0; + + cred = prepare_creds(); + if (cred) { + err = create_user_ns(cred); + if (err) + put_cred(cred); + else + *new_cred = cred; + } + + return err; +} + +void free_user_ns(struct user_namespace *ns) +{ + struct user_namespace *parent; + + do { + parent = ns->parent; +#ifdef CONFIG_PERSISTENT_KEYRINGS + key_put(ns->persistent_keyring_register); +#endif + ns_free_inum(&ns->ns); + kmem_cache_free(user_ns_cachep, ns); + ns = parent; + } while (atomic_dec_and_test(&parent->count)); +} +EXPORT_SYMBOL(free_user_ns); + +static u32 map_id_range_down(struct uid_gid_map *map, u32 id, u32 count) +{ + unsigned idx, extents; + u32 first, last, id2; + + id2 = id + count - 1; + + /* Find the matching extent */ + extents = map->nr_extents; + smp_rmb(); + for (idx = 0; idx < extents; idx++) { + first = map->extent[idx].first; + last = first + map->extent[idx].count - 1; + if (id >= first && id <= last && + (id2 >= first && id2 <= last)) + break; + } + /* Map the id or note failure */ + if (idx < extents) + id = (id - first) + map->extent[idx].lower_first; + else + id = (u32) -1; + + return id; +} + +static u32 map_id_down(struct uid_gid_map *map, u32 id) +{ + unsigned idx, extents; + u32 first, last; + + /* Find the matching extent */ + extents = map->nr_extents; + smp_rmb(); + for (idx = 0; idx < extents; idx++) { + first = map->extent[idx].first; + last = first + map->extent[idx].count - 1; + if (id >= first && id <= last) + break; + } + /* Map the id or note failure */ + if (idx < extents) + id = (id - first) + map->extent[idx].lower_first; + else + id = (u32) -1; + + return id; +} + +static u32 map_id_up(struct uid_gid_map *map, u32 id) +{ + unsigned idx, extents; + u32 first, last; + + /* Find the matching extent */ + extents = map->nr_extents; + smp_rmb(); + for (idx = 0; idx < extents; idx++) { + first = map->extent[idx].lower_first; + last = first + map->extent[idx].count - 1; + if (id >= first && id <= last) + break; + } + /* Map the id or note failure */ + if (idx < extents) + id = (id - first) + map->extent[idx].first; + else + id = (u32) -1; + + return id; +} + +/** + * make_kuid - Map a user-namespace uid pair into a kuid. + * @ns: User namespace that the uid is in + * @uid: User identifier + * + * Maps a user-namespace uid pair into a kernel internal kuid, + * and returns that kuid. + * + * When there is no mapping defined for the user-namespace uid + * pair INVALID_UID is returned. Callers are expected to test + * for and handle INVALID_UID being returned. INVALID_UID + * may be tested for using uid_valid(). + */ +kuid_t make_kuid(struct user_namespace *ns, uid_t uid) +{ + /* Map the uid to a global kernel uid */ + return KUIDT_INIT(map_id_down(&ns->uid_map, uid)); +} +EXPORT_SYMBOL(make_kuid); + +/** + * from_kuid - Create a uid from a kuid user-namespace pair. + * @targ: The user namespace we want a uid in. + * @kuid: The kernel internal uid to start with. + * + * Map @kuid into the user-namespace specified by @targ and + * return the resulting uid. + * + * There is always a mapping into the initial user_namespace. + * + * If @kuid has no mapping in @targ (uid_t)-1 is returned. + */ +uid_t from_kuid(struct user_namespace *targ, kuid_t kuid) +{ + /* Map the uid from a global kernel uid */ + return map_id_up(&targ->uid_map, __kuid_val(kuid)); +} +EXPORT_SYMBOL(from_kuid); + +/** + * from_kuid_munged - Create a uid from a kuid user-namespace pair. + * @targ: The user namespace we want a uid in. + * @kuid: The kernel internal uid to start with. + * + * Map @kuid into the user-namespace specified by @targ and + * return the resulting uid. + * + * There is always a mapping into the initial user_namespace. + * + * Unlike from_kuid from_kuid_munged never fails and always + * returns a valid uid. This makes from_kuid_munged appropriate + * for use in syscalls like stat and getuid where failing the + * system call and failing to provide a valid uid are not an + * options. + * + * If @kuid has no mapping in @targ overflowuid is returned. + */ +uid_t from_kuid_munged(struct user_namespace *targ, kuid_t kuid) +{ + uid_t uid; + uid = from_kuid(targ, kuid); + + if (uid == (uid_t) -1) + uid = overflowuid; + return uid; +} +EXPORT_SYMBOL(from_kuid_munged); + +/** + * make_kgid - Map a user-namespace gid pair into a kgid. + * @ns: User namespace that the gid is in + * @gid: group identifier + * + * Maps a user-namespace gid pair into a kernel internal kgid, + * and returns that kgid. + * + * When there is no mapping defined for the user-namespace gid + * pair INVALID_GID is returned. Callers are expected to test + * for and handle INVALID_GID being returned. INVALID_GID may be + * tested for using gid_valid(). + */ +kgid_t make_kgid(struct user_namespace *ns, gid_t gid) +{ + /* Map the gid to a global kernel gid */ + return KGIDT_INIT(map_id_down(&ns->gid_map, gid)); +} +EXPORT_SYMBOL(make_kgid); + +/** + * from_kgid - Create a gid from a kgid user-namespace pair. + * @targ: The user namespace we want a gid in. + * @kgid: The kernel internal gid to start with. + * + * Map @kgid into the user-namespace specified by @targ and + * return the resulting gid. + * + * There is always a mapping into the initial user_namespace. + * + * If @kgid has no mapping in @targ (gid_t)-1 is returned. + */ +gid_t from_kgid(struct user_namespace *targ, kgid_t kgid) +{ + /* Map the gid from a global kernel gid */ + return map_id_up(&targ->gid_map, __kgid_val(kgid)); +} +EXPORT_SYMBOL(from_kgid); + +/** + * from_kgid_munged - Create a gid from a kgid user-namespace pair. + * @targ: The user namespace we want a gid in. + * @kgid: The kernel internal gid to start with. + * + * Map @kgid into the user-namespace specified by @targ and + * return the resulting gid. + * + * There is always a mapping into the initial user_namespace. + * + * Unlike from_kgid from_kgid_munged never fails and always + * returns a valid gid. This makes from_kgid_munged appropriate + * for use in syscalls like stat and getgid where failing the + * system call and failing to provide a valid gid are not options. + * + * If @kgid has no mapping in @targ overflowgid is returned. + */ +gid_t from_kgid_munged(struct user_namespace *targ, kgid_t kgid) +{ + gid_t gid; + gid = from_kgid(targ, kgid); + + if (gid == (gid_t) -1) + gid = overflowgid; + return gid; +} +EXPORT_SYMBOL(from_kgid_munged); + +/** + * make_kprojid - Map a user-namespace projid pair into a kprojid. + * @ns: User namespace that the projid is in + * @projid: Project identifier + * + * Maps a user-namespace uid pair into a kernel internal kuid, + * and returns that kuid. + * + * When there is no mapping defined for the user-namespace projid + * pair INVALID_PROJID is returned. Callers are expected to test + * for and handle handle INVALID_PROJID being returned. INVALID_PROJID + * may be tested for using projid_valid(). + */ +kprojid_t make_kprojid(struct user_namespace *ns, projid_t projid) +{ + /* Map the uid to a global kernel uid */ + return KPROJIDT_INIT(map_id_down(&ns->projid_map, projid)); +} +EXPORT_SYMBOL(make_kprojid); + +/** + * from_kprojid - Create a projid from a kprojid user-namespace pair. + * @targ: The user namespace we want a projid in. + * @kprojid: The kernel internal project identifier to start with. + * + * Map @kprojid into the user-namespace specified by @targ and + * return the resulting projid. + * + * There is always a mapping into the initial user_namespace. + * + * If @kprojid has no mapping in @targ (projid_t)-1 is returned. + */ +projid_t from_kprojid(struct user_namespace *targ, kprojid_t kprojid) +{ + /* Map the uid from a global kernel uid */ + return map_id_up(&targ->projid_map, __kprojid_val(kprojid)); +} +EXPORT_SYMBOL(from_kprojid); + +/** + * from_kprojid_munged - Create a projiid from a kprojid user-namespace pair. + * @targ: The user namespace we want a projid in. + * @kprojid: The kernel internal projid to start with. + * + * Map @kprojid into the user-namespace specified by @targ and + * return the resulting projid. + * + * There is always a mapping into the initial user_namespace. + * + * Unlike from_kprojid from_kprojid_munged never fails and always + * returns a valid projid. This makes from_kprojid_munged + * appropriate for use in syscalls like stat and where + * failing the system call and failing to provide a valid projid are + * not an options. + * + * If @kprojid has no mapping in @targ OVERFLOW_PROJID is returned. + */ +projid_t from_kprojid_munged(struct user_namespace *targ, kprojid_t kprojid) +{ + projid_t projid; + projid = from_kprojid(targ, kprojid); + + if (projid == (projid_t) -1) + projid = OVERFLOW_PROJID; + return projid; +} +EXPORT_SYMBOL(from_kprojid_munged); + + +static int uid_m_show(struct seq_file *seq, void *v) +{ + struct user_namespace *ns = seq->private; + struct uid_gid_extent *extent = v; + struct user_namespace *lower_ns; + uid_t lower; + + lower_ns = seq_user_ns(seq); + if ((lower_ns == ns) && lower_ns->parent) + lower_ns = lower_ns->parent; + + lower = from_kuid(lower_ns, KUIDT_INIT(extent->lower_first)); + + seq_printf(seq, "%10u %10u %10u\n", + extent->first, + lower, + extent->count); + + return 0; +} + +static int gid_m_show(struct seq_file *seq, void *v) +{ + struct user_namespace *ns = seq->private; + struct uid_gid_extent *extent = v; + struct user_namespace *lower_ns; + gid_t lower; + + lower_ns = seq_user_ns(seq); + if ((lower_ns == ns) && lower_ns->parent) + lower_ns = lower_ns->parent; + + lower = from_kgid(lower_ns, KGIDT_INIT(extent->lower_first)); + + seq_printf(seq, "%10u %10u %10u\n", + extent->first, + lower, + extent->count); + + return 0; +} + +static int projid_m_show(struct seq_file *seq, void *v) +{ + struct user_namespace *ns = seq->private; + struct uid_gid_extent *extent = v; + struct user_namespace *lower_ns; + projid_t lower; + + lower_ns = seq_user_ns(seq); + if ((lower_ns == ns) && lower_ns->parent) + lower_ns = lower_ns->parent; + + lower = from_kprojid(lower_ns, KPROJIDT_INIT(extent->lower_first)); + + seq_printf(seq, "%10u %10u %10u\n", + extent->first, + lower, + extent->count); + + return 0; +} + +static void *m_start(struct seq_file *seq, loff_t *ppos, + struct uid_gid_map *map) +{ + struct uid_gid_extent *extent = NULL; + loff_t pos = *ppos; + + if (pos < map->nr_extents) + extent = &map->extent[pos]; + + return extent; +} + +static void *uid_m_start(struct seq_file *seq, loff_t *ppos) +{ + struct user_namespace *ns = seq->private; + + return m_start(seq, ppos, &ns->uid_map); +} + +static void *gid_m_start(struct seq_file *seq, loff_t *ppos) +{ + struct user_namespace *ns = seq->private; + + return m_start(seq, ppos, &ns->gid_map); +} + +static void *projid_m_start(struct seq_file *seq, loff_t *ppos) +{ + struct user_namespace *ns = seq->private; + + return m_start(seq, ppos, &ns->projid_map); +} + +static void *m_next(struct seq_file *seq, void *v, loff_t *pos) +{ + (*pos)++; + return seq->op->start(seq, pos); +} + +static void m_stop(struct seq_file *seq, void *v) +{ + return; +} + +const struct seq_operations proc_uid_seq_operations = { + .start = uid_m_start, + .stop = m_stop, + .next = m_next, + .show = uid_m_show, +}; + +const struct seq_operations proc_gid_seq_operations = { + .start = gid_m_start, + .stop = m_stop, + .next = m_next, + .show = gid_m_show, +}; + +const struct seq_operations proc_projid_seq_operations = { + .start = projid_m_start, + .stop = m_stop, + .next = m_next, + .show = projid_m_show, +}; + +static bool mappings_overlap(struct uid_gid_map *new_map, + struct uid_gid_extent *extent) +{ + u32 upper_first, lower_first, upper_last, lower_last; + unsigned idx; + + upper_first = extent->first; + lower_first = extent->lower_first; + upper_last = upper_first + extent->count - 1; + lower_last = lower_first + extent->count - 1; + + for (idx = 0; idx < new_map->nr_extents; idx++) { + u32 prev_upper_first, prev_lower_first; + u32 prev_upper_last, prev_lower_last; + struct uid_gid_extent *prev; + + prev = &new_map->extent[idx]; + + prev_upper_first = prev->first; + prev_lower_first = prev->lower_first; + prev_upper_last = prev_upper_first + prev->count - 1; + prev_lower_last = prev_lower_first + prev->count - 1; + + /* Does the upper range intersect a previous extent? */ + if ((prev_upper_first <= upper_last) && + (prev_upper_last >= upper_first)) + return true; + + /* Does the lower range intersect a previous extent? */ + if ((prev_lower_first <= lower_last) && + (prev_lower_last >= lower_first)) + return true; + } + return false; +} + +static ssize_t map_write(struct file *file, const char __user *buf, + size_t count, loff_t *ppos, + int cap_setid, + struct uid_gid_map *map, + struct uid_gid_map *parent_map) +{ + struct seq_file *seq = file->private_data; + struct user_namespace *ns = seq->private; + struct uid_gid_map new_map; + unsigned idx; + struct uid_gid_extent *extent = NULL; + unsigned long page = 0; + char *kbuf, *pos, *next_line; + ssize_t ret = -EINVAL; + + /* + * The userns_state_mutex serializes all writes to any given map. + * + * Any map is only ever written once. + * + * An id map fits within 1 cache line on most architectures. + * + * On read nothing needs to be done unless you are on an + * architecture with a crazy cache coherency model like alpha. + * + * There is a one time data dependency between reading the + * count of the extents and the values of the extents. The + * desired behavior is to see the values of the extents that + * were written before the count of the extents. + * + * To achieve this smp_wmb() is used on guarantee the write + * order and smp_rmb() is guaranteed that we don't have crazy + * architectures returning stale data. + */ + mutex_lock(&userns_state_mutex); + + ret = -EPERM; + /* Only allow one successful write to the map */ + if (map->nr_extents != 0) + goto out; + + /* + * Adjusting namespace settings requires capabilities on the target. + */ + if (cap_valid(cap_setid) && !file_ns_capable(file, ns, CAP_SYS_ADMIN)) + goto out; + + /* Get a buffer */ + ret = -ENOMEM; + page = __get_free_page(GFP_TEMPORARY); + kbuf = (char *) page; + if (!page) + goto out; + + /* Only allow < page size writes at the beginning of the file */ + ret = -EINVAL; + if ((*ppos != 0) || (count >= PAGE_SIZE)) + goto out; + + /* Slurp in the user data */ + ret = -EFAULT; + if (copy_from_user(kbuf, buf, count)) + goto out; + kbuf[count] = '\0'; + + /* Parse the user data */ + ret = -EINVAL; + pos = kbuf; + new_map.nr_extents = 0; + for (; pos; pos = next_line) { + extent = &new_map.extent[new_map.nr_extents]; + + /* Find the end of line and ensure I don't look past it */ + next_line = strchr(pos, '\n'); + if (next_line) { + *next_line = '\0'; + next_line++; + if (*next_line == '\0') + next_line = NULL; + } + + pos = skip_spaces(pos); + extent->first = simple_strtoul(pos, &pos, 10); + if (!isspace(*pos)) + goto out; + + pos = skip_spaces(pos); + extent->lower_first = simple_strtoul(pos, &pos, 10); + if (!isspace(*pos)) + goto out; + + pos = skip_spaces(pos); + extent->count = simple_strtoul(pos, &pos, 10); + if (*pos && !isspace(*pos)) + goto out; + + /* Verify there is not trailing junk on the line */ + pos = skip_spaces(pos); + if (*pos != '\0') + goto out; + + /* Verify we have been given valid starting values */ + if ((extent->first == (u32) -1) || + (extent->lower_first == (u32) -1)) + goto out; + + /* Verify count is not zero and does not cause the + * extent to wrap + */ + if ((extent->first + extent->count) <= extent->first) + goto out; + if ((extent->lower_first + extent->count) <= + extent->lower_first) + goto out; + + /* Do the ranges in extent overlap any previous extents? */ + if (mappings_overlap(&new_map, extent)) + goto out; + + new_map.nr_extents++; + + /* Fail if the file contains too many extents */ + if ((new_map.nr_extents == UID_GID_MAP_MAX_EXTENTS) && + (next_line != NULL)) + goto out; + } + /* Be very certaint the new map actually exists */ + if (new_map.nr_extents == 0) + goto out; + + ret = -EPERM; + /* Validate the user is allowed to use user id's mapped to. */ + if (!new_idmap_permitted(file, ns, cap_setid, &new_map)) + goto out; + + /* Map the lower ids from the parent user namespace to the + * kernel global id space. + */ + for (idx = 0; idx < new_map.nr_extents; idx++) { + u32 lower_first; + extent = &new_map.extent[idx]; + + lower_first = map_id_range_down(parent_map, + extent->lower_first, + extent->count); + + /* Fail if we can not map the specified extent to + * the kernel global id space. + */ + if (lower_first == (u32) -1) + goto out; + + extent->lower_first = lower_first; + } + + /* Install the map */ + memcpy(map->extent, new_map.extent, + new_map.nr_extents*sizeof(new_map.extent[0])); + smp_wmb(); + map->nr_extents = new_map.nr_extents; + + *ppos = count; + ret = count; +out: + mutex_unlock(&userns_state_mutex); + if (page) + free_page(page); + return ret; +} + +ssize_t proc_uid_map_write(struct file *file, const char __user *buf, + size_t size, loff_t *ppos) +{ + struct seq_file *seq = file->private_data; + struct user_namespace *ns = seq->private; + struct user_namespace *seq_ns = seq_user_ns(seq); + + if (!ns->parent) + return -EPERM; + + if ((seq_ns != ns) && (seq_ns != ns->parent)) + return -EPERM; + + return map_write(file, buf, size, ppos, CAP_SETUID, + &ns->uid_map, &ns->parent->uid_map); +} + +ssize_t proc_gid_map_write(struct file *file, const char __user *buf, + size_t size, loff_t *ppos) +{ + struct seq_file *seq = file->private_data; + struct user_namespace *ns = seq->private; + struct user_namespace *seq_ns = seq_user_ns(seq); + + if (!ns->parent) + return -EPERM; + + if ((seq_ns != ns) && (seq_ns != ns->parent)) + return -EPERM; + + return map_write(file, buf, size, ppos, CAP_SETGID, + &ns->gid_map, &ns->parent->gid_map); +} + +ssize_t proc_projid_map_write(struct file *file, const char __user *buf, + size_t size, loff_t *ppos) +{ + struct seq_file *seq = file->private_data; + struct user_namespace *ns = seq->private; + struct user_namespace *seq_ns = seq_user_ns(seq); + + if (!ns->parent) + return -EPERM; + + if ((seq_ns != ns) && (seq_ns != ns->parent)) + return -EPERM; + + /* Anyone can set any valid project id no capability needed */ + return map_write(file, buf, size, ppos, -1, + &ns->projid_map, &ns->parent->projid_map); +} + +static bool new_idmap_permitted(const struct file *file, + struct user_namespace *ns, int cap_setid, + struct uid_gid_map *new_map) +{ + const struct cred *cred = file->f_cred; + /* Don't allow mappings that would allow anything that wouldn't + * be allowed without the establishment of unprivileged mappings. + */ + if ((new_map->nr_extents == 1) && (new_map->extent[0].count == 1) && + uid_eq(ns->owner, cred->euid)) { + u32 id = new_map->extent[0].lower_first; + if (cap_setid == CAP_SETUID) { + kuid_t uid = make_kuid(ns->parent, id); + if (uid_eq(uid, cred->euid)) + return true; + } else if (cap_setid == CAP_SETGID) { + kgid_t gid = make_kgid(ns->parent, id); + if (!(ns->flags & USERNS_SETGROUPS_ALLOWED) && + gid_eq(gid, cred->egid)) + return true; + } + } + + /* Allow anyone to set a mapping that doesn't require privilege */ + if (!cap_valid(cap_setid)) + return true; + + /* Allow the specified ids if we have the appropriate capability + * (CAP_SETUID or CAP_SETGID) over the parent user namespace. + * And the opener of the id file also had the approprpiate capability. + */ + if (ns_capable(ns->parent, cap_setid) && + file_ns_capable(file, ns->parent, cap_setid)) + return true; + + return false; +} + +int proc_setgroups_show(struct seq_file *seq, void *v) +{ + struct user_namespace *ns = seq->private; + unsigned long userns_flags = ACCESS_ONCE(ns->flags); + + seq_printf(seq, "%s\n", + (userns_flags & USERNS_SETGROUPS_ALLOWED) ? + "allow" : "deny"); + return 0; +} + +ssize_t proc_setgroups_write(struct file *file, const char __user *buf, + size_t count, loff_t *ppos) +{ + struct seq_file *seq = file->private_data; + struct user_namespace *ns = seq->private; + char kbuf[8], *pos; + bool setgroups_allowed; + ssize_t ret; + + /* Only allow a very narrow range of strings to be written */ + ret = -EINVAL; + if ((*ppos != 0) || (count >= sizeof(kbuf))) + goto out; + + /* What was written? */ + ret = -EFAULT; + if (copy_from_user(kbuf, buf, count)) + goto out; + kbuf[count] = '\0'; + pos = kbuf; + + /* What is being requested? */ + ret = -EINVAL; + if (strncmp(pos, "allow", 5) == 0) { + pos += 5; + setgroups_allowed = true; + } + else if (strncmp(pos, "deny", 4) == 0) { + pos += 4; + setgroups_allowed = false; + } + else + goto out; + + /* Verify there is not trailing junk on the line */ + pos = skip_spaces(pos); + if (*pos != '\0') + goto out; + + ret = -EPERM; + mutex_lock(&userns_state_mutex); + if (setgroups_allowed) { + /* Enabling setgroups after setgroups has been disabled + * is not allowed. + */ + if (!(ns->flags & USERNS_SETGROUPS_ALLOWED)) + goto out_unlock; + } else { + /* Permanently disabling setgroups after setgroups has + * been enabled by writing the gid_map is not allowed. + */ + if (ns->gid_map.nr_extents != 0) + goto out_unlock; + ns->flags &= ~USERNS_SETGROUPS_ALLOWED; + } + mutex_unlock(&userns_state_mutex); + + /* Report a successful write */ + *ppos = count; + ret = count; +out: + return ret; +out_unlock: + mutex_unlock(&userns_state_mutex); + goto out; +} + +bool userns_may_setgroups(const struct user_namespace *ns) +{ + bool allowed; + + mutex_lock(&userns_state_mutex); + /* It is not safe to use setgroups until a gid mapping in + * the user namespace has been established. + */ + allowed = ns->gid_map.nr_extents != 0; + /* Is setgroups allowed? */ + allowed = allowed && (ns->flags & USERNS_SETGROUPS_ALLOWED); + mutex_unlock(&userns_state_mutex); + + return allowed; +} + +static inline struct user_namespace *to_user_ns(struct ns_common *ns) +{ + return container_of(ns, struct user_namespace, ns); +} + +static struct ns_common *userns_get(struct task_struct *task) +{ + struct user_namespace *user_ns; + + rcu_read_lock(); + user_ns = get_user_ns(__task_cred(task)->user_ns); + rcu_read_unlock(); + + return user_ns ? &user_ns->ns : NULL; +} + +static void userns_put(struct ns_common *ns) +{ + put_user_ns(to_user_ns(ns)); +} + +static int userns_install(struct nsproxy *nsproxy, struct ns_common *ns) +{ + struct user_namespace *user_ns = to_user_ns(ns); + struct cred *cred; + + /* Don't allow gaining capabilities by reentering + * the same user namespace. + */ + if (user_ns == current_user_ns()) + return -EINVAL; + + /* Threaded processes may not enter a different user namespace */ + if (atomic_read(¤t->mm->mm_users) > 1) + return -EINVAL; + + if (current->fs->users != 1) + return -EINVAL; + + if (!ns_capable(user_ns, CAP_SYS_ADMIN)) + return -EPERM; + + cred = prepare_creds(); + if (!cred) + return -ENOMEM; + + put_user_ns(cred->user_ns); + set_cred_user_ns(cred, get_user_ns(user_ns)); + + return commit_creds(cred); +} + +const struct proc_ns_operations userns_operations = { + .name = "user", + .type = CLONE_NEWUSER, + .get = userns_get, + .put = userns_put, + .install = userns_install, +}; + +static __init int user_namespaces_init(void) +{ + user_ns_cachep = KMEM_CACHE(user_namespace, SLAB_PANIC); + return 0; +} +subsys_initcall(user_namespaces_init); |