diff options
Diffstat (limited to 'kernel/user_namespace.c')
| -rw-r--r-- | kernel/user_namespace.c | 1408 |
1 files changed, 1408 insertions, 0 deletions
diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c new file mode 100644 index 000000000..54211dbd5 --- /dev/null +++ b/kernel/user_namespace.c @@ -0,0 +1,1408 @@ +// SPDX-License-Identifier: GPL-2.0-only + +#include <linux/export.h> +#include <linux/nsproxy.h> +#include <linux/slab.h> +#include <linux/sched/signal.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/security.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> +#include <linux/bsearch.h> +#include <linux/sort.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 free_user_ns(struct work_struct *work); + +static struct ucounts *inc_user_namespaces(struct user_namespace *ns, kuid_t uid) +{ + return inc_ucount(ns, uid, UCOUNT_USER_NAMESPACES); +} + +static void dec_user_namespaces(struct ucounts *ucounts) +{ + return dec_ucount(ucounts, UCOUNT_USER_NAMESPACES); +} + +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_ambient = CAP_EMPTY_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; +} + +static unsigned long enforced_nproc_rlimit(void) +{ + unsigned long limit = RLIM_INFINITY; + + /* Is RLIMIT_NPROC currently enforced? */ + if (!uid_eq(current_uid(), GLOBAL_ROOT_UID) || + (current_user_ns() != &init_user_ns)) + limit = rlimit(RLIMIT_NPROC); + + return limit; +} + +/* + * 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; + struct ucounts *ucounts; + int ret, i; + + ret = -ENOSPC; + if (parent_ns->level > 32) + goto fail; + + ucounts = inc_user_namespaces(parent_ns, owner); + if (!ucounts) + goto fail; + + /* + * Verify that we can not violate the policy of which files + * may be accessed that is specified by the root directory, + * by verifying that the root directory is at the root of the + * mount namespace which allows all files to be accessed. + */ + ret = -EPERM; + if (current_chrooted()) + goto fail_dec; + + /* 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. + */ + ret = -EPERM; + if (!kuid_has_mapping(parent_ns, owner) || + !kgid_has_mapping(parent_ns, group)) + goto fail_dec; + + ret = security_create_user_ns(new); + if (ret < 0) + goto fail_dec; + + ret = -ENOMEM; + ns = kmem_cache_zalloc(user_ns_cachep, GFP_KERNEL); + if (!ns) + goto fail_dec; + + ns->parent_could_setfcap = cap_raised(new->cap_effective, CAP_SETFCAP); + ret = ns_alloc_inum(&ns->ns); + if (ret) + goto fail_free; + ns->ns.ops = &userns_operations; + + refcount_set(&ns->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; + INIT_WORK(&ns->work, free_user_ns); + for (i = 0; i < UCOUNT_COUNTS; i++) { + ns->ucount_max[i] = INT_MAX; + } + set_userns_rlimit_max(ns, UCOUNT_RLIMIT_NPROC, enforced_nproc_rlimit()); + set_userns_rlimit_max(ns, UCOUNT_RLIMIT_MSGQUEUE, rlimit(RLIMIT_MSGQUEUE)); + set_userns_rlimit_max(ns, UCOUNT_RLIMIT_SIGPENDING, rlimit(RLIMIT_SIGPENDING)); + set_userns_rlimit_max(ns, UCOUNT_RLIMIT_MEMLOCK, rlimit(RLIMIT_MEMLOCK)); + ns->ucounts = ucounts; + + /* Inherit USERNS_SETGROUPS_ALLOWED from our parent */ + mutex_lock(&userns_state_mutex); + ns->flags = parent_ns->flags; + mutex_unlock(&userns_state_mutex); + +#ifdef CONFIG_KEYS + INIT_LIST_HEAD(&ns->keyring_name_list); + init_rwsem(&ns->keyring_sem); +#endif + ret = -ENOMEM; + if (!setup_userns_sysctls(ns)) + goto fail_keyring; + + set_cred_user_ns(new, ns); + return 0; +fail_keyring: +#ifdef CONFIG_PERSISTENT_KEYRINGS + key_put(ns->persistent_keyring_register); +#endif + ns_free_inum(&ns->ns); +fail_free: + kmem_cache_free(user_ns_cachep, ns); +fail_dec: + dec_user_namespaces(ucounts); +fail: + return ret; +} + +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; +} + +static void free_user_ns(struct work_struct *work) +{ + struct user_namespace *parent, *ns = + container_of(work, struct user_namespace, work); + + do { + struct ucounts *ucounts = ns->ucounts; + parent = ns->parent; + if (ns->gid_map.nr_extents > UID_GID_MAP_MAX_BASE_EXTENTS) { + kfree(ns->gid_map.forward); + kfree(ns->gid_map.reverse); + } + if (ns->uid_map.nr_extents > UID_GID_MAP_MAX_BASE_EXTENTS) { + kfree(ns->uid_map.forward); + kfree(ns->uid_map.reverse); + } + if (ns->projid_map.nr_extents > UID_GID_MAP_MAX_BASE_EXTENTS) { + kfree(ns->projid_map.forward); + kfree(ns->projid_map.reverse); + } + retire_userns_sysctls(ns); + key_free_user_ns(ns); + ns_free_inum(&ns->ns); + kmem_cache_free(user_ns_cachep, ns); + dec_user_namespaces(ucounts); + ns = parent; + } while (refcount_dec_and_test(&parent->ns.count)); +} + +void __put_user_ns(struct user_namespace *ns) +{ + schedule_work(&ns->work); +} +EXPORT_SYMBOL(__put_user_ns); + +/** + * idmap_key struct holds the information necessary to find an idmapping in a + * sorted idmap array. It is passed to cmp_map_id() as first argument. + */ +struct idmap_key { + bool map_up; /* true -> id from kid; false -> kid from id */ + u32 id; /* id to find */ + u32 count; /* == 0 unless used with map_id_range_down() */ +}; + +/** + * cmp_map_id - Function to be passed to bsearch() to find the requested + * idmapping. Expects struct idmap_key to be passed via @k. + */ +static int cmp_map_id(const void *k, const void *e) +{ + u32 first, last, id2; + const struct idmap_key *key = k; + const struct uid_gid_extent *el = e; + + id2 = key->id + key->count - 1; + + /* handle map_id_{down,up}() */ + if (key->map_up) + first = el->lower_first; + else + first = el->first; + + last = first + el->count - 1; + + if (key->id >= first && key->id <= last && + (id2 >= first && id2 <= last)) + return 0; + + if (key->id < first || id2 < first) + return -1; + + return 1; +} + +/** + * map_id_range_down_max - Find idmap via binary search in ordered idmap array. + * Can only be called if number of mappings exceeds UID_GID_MAP_MAX_BASE_EXTENTS. + */ +static struct uid_gid_extent * +map_id_range_down_max(unsigned extents, struct uid_gid_map *map, u32 id, u32 count) +{ + struct idmap_key key; + + key.map_up = false; + key.count = count; + key.id = id; + + return bsearch(&key, map->forward, extents, + sizeof(struct uid_gid_extent), cmp_map_id); +} + +/** + * map_id_range_down_base - Find idmap via binary search in static extent array. + * Can only be called if number of mappings is equal or less than + * UID_GID_MAP_MAX_BASE_EXTENTS. + */ +static struct uid_gid_extent * +map_id_range_down_base(unsigned extents, struct uid_gid_map *map, u32 id, u32 count) +{ + unsigned idx; + u32 first, last, id2; + + id2 = id + count - 1; + + /* Find the matching extent */ + 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)) + return &map->extent[idx]; + } + return NULL; +} + +static u32 map_id_range_down(struct uid_gid_map *map, u32 id, u32 count) +{ + struct uid_gid_extent *extent; + unsigned extents = map->nr_extents; + smp_rmb(); + + if (extents <= UID_GID_MAP_MAX_BASE_EXTENTS) + extent = map_id_range_down_base(extents, map, id, count); + else + extent = map_id_range_down_max(extents, map, id, count); + + /* Map the id or note failure */ + if (extent) + id = (id - extent->first) + extent->lower_first; + else + id = (u32) -1; + + return id; +} + +static u32 map_id_down(struct uid_gid_map *map, u32 id) +{ + return map_id_range_down(map, id, 1); +} + +/** + * map_id_up_base - Find idmap via binary search in static extent array. + * Can only be called if number of mappings is equal or less than + * UID_GID_MAP_MAX_BASE_EXTENTS. + */ +static struct uid_gid_extent * +map_id_up_base(unsigned extents, struct uid_gid_map *map, u32 id) +{ + unsigned idx; + u32 first, last; + + /* Find the matching extent */ + for (idx = 0; idx < extents; idx++) { + first = map->extent[idx].lower_first; + last = first + map->extent[idx].count - 1; + if (id >= first && id <= last) + return &map->extent[idx]; + } + return NULL; +} + +/** + * map_id_up_max - Find idmap via binary search in ordered idmap array. + * Can only be called if number of mappings exceeds UID_GID_MAP_MAX_BASE_EXTENTS. + */ +static struct uid_gid_extent * +map_id_up_max(unsigned extents, struct uid_gid_map *map, u32 id) +{ + struct idmap_key key; + + key.map_up = true; + key.count = 1; + key.id = id; + + return bsearch(&key, map->reverse, extents, + sizeof(struct uid_gid_extent), cmp_map_id); +} + +static u32 map_id_up(struct uid_gid_map *map, u32 id) +{ + struct uid_gid_extent *extent; + unsigned extents = map->nr_extents; + smp_rmb(); + + if (extents <= UID_GID_MAP_MAX_BASE_EXTENTS) + extent = map_id_up_base(extents, map, id); + else + extent = map_id_up_max(extents, map, id); + + /* Map the id or note failure */ + if (extent) + id = (id - extent->lower_first) + extent->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 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) +{ + loff_t pos = *ppos; + unsigned extents = map->nr_extents; + smp_rmb(); + + if (pos >= extents) + return NULL; + + if (extents <= UID_GID_MAP_MAX_BASE_EXTENTS) + return &map->extent[pos]; + + return &map->forward[pos]; +} + +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; + + if (new_map->nr_extents <= UID_GID_MAP_MAX_BASE_EXTENTS) + prev = &new_map->extent[idx]; + else + prev = &new_map->forward[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; +} + +/** + * insert_extent - Safely insert a new idmap extent into struct uid_gid_map. + * Takes care to allocate a 4K block of memory if the number of mappings exceeds + * UID_GID_MAP_MAX_BASE_EXTENTS. + */ +static int insert_extent(struct uid_gid_map *map, struct uid_gid_extent *extent) +{ + struct uid_gid_extent *dest; + + if (map->nr_extents == UID_GID_MAP_MAX_BASE_EXTENTS) { + struct uid_gid_extent *forward; + + /* Allocate memory for 340 mappings. */ + forward = kmalloc_array(UID_GID_MAP_MAX_EXTENTS, + sizeof(struct uid_gid_extent), + GFP_KERNEL); + if (!forward) + return -ENOMEM; + + /* Copy over memory. Only set up memory for the forward pointer. + * Defer the memory setup for the reverse pointer. + */ + memcpy(forward, map->extent, + map->nr_extents * sizeof(map->extent[0])); + + map->forward = forward; + map->reverse = NULL; + } + + if (map->nr_extents < UID_GID_MAP_MAX_BASE_EXTENTS) + dest = &map->extent[map->nr_extents]; + else + dest = &map->forward[map->nr_extents]; + + *dest = *extent; + map->nr_extents++; + return 0; +} + +/* cmp function to sort() forward mappings */ +static int cmp_extents_forward(const void *a, const void *b) +{ + const struct uid_gid_extent *e1 = a; + const struct uid_gid_extent *e2 = b; + + if (e1->first < e2->first) + return -1; + + if (e1->first > e2->first) + return 1; + + return 0; +} + +/* cmp function to sort() reverse mappings */ +static int cmp_extents_reverse(const void *a, const void *b) +{ + const struct uid_gid_extent *e1 = a; + const struct uid_gid_extent *e2 = b; + + if (e1->lower_first < e2->lower_first) + return -1; + + if (e1->lower_first > e2->lower_first) + return 1; + + return 0; +} + +/** + * sort_idmaps - Sorts an array of idmap entries. + * Can only be called if number of mappings exceeds UID_GID_MAP_MAX_BASE_EXTENTS. + */ +static int sort_idmaps(struct uid_gid_map *map) +{ + if (map->nr_extents <= UID_GID_MAP_MAX_BASE_EXTENTS) + return 0; + + /* Sort forward array. */ + sort(map->forward, map->nr_extents, sizeof(struct uid_gid_extent), + cmp_extents_forward, NULL); + + /* Only copy the memory from forward we actually need. */ + map->reverse = kmemdup(map->forward, + map->nr_extents * sizeof(struct uid_gid_extent), + GFP_KERNEL); + if (!map->reverse) + return -ENOMEM; + + /* Sort reverse array. */ + sort(map->reverse, map->nr_extents, sizeof(struct uid_gid_extent), + cmp_extents_reverse, NULL); + + return 0; +} + +/** + * verify_root_map() - check the uid 0 mapping + * @file: idmapping file + * @map_ns: user namespace of the target process + * @new_map: requested idmap + * + * If a process requests mapping parent uid 0 into the new ns, verify that the + * process writing the map had the CAP_SETFCAP capability as the target process + * will be able to write fscaps that are valid in ancestor user namespaces. + * + * Return: true if the mapping is allowed, false if not. + */ +static bool verify_root_map(const struct file *file, + struct user_namespace *map_ns, + struct uid_gid_map *new_map) +{ + int idx; + const struct user_namespace *file_ns = file->f_cred->user_ns; + struct uid_gid_extent *extent0 = NULL; + + for (idx = 0; idx < new_map->nr_extents; idx++) { + if (new_map->nr_extents <= UID_GID_MAP_MAX_BASE_EXTENTS) + extent0 = &new_map->extent[idx]; + else + extent0 = &new_map->forward[idx]; + if (extent0->lower_first == 0) + break; + + extent0 = NULL; + } + + if (!extent0) + return true; + + if (map_ns == file_ns) { + /* The process unshared its ns and is writing to its own + * /proc/self/uid_map. User already has full capabilites in + * the new namespace. Verify that the parent had CAP_SETFCAP + * when it unshared. + * */ + if (!file_ns->parent_could_setfcap) + return false; + } else { + /* Process p1 is writing to uid_map of p2, who is in a child + * user namespace to p1's. Verify that the opener of the map + * file has CAP_SETFCAP against the parent of the new map + * namespace */ + if (!file_ns_capable(file, map_ns->parent, CAP_SETFCAP)) + return false; + } + + return true; +} + +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 *map_ns = seq->private; + struct uid_gid_map new_map; + unsigned idx; + struct uid_gid_extent extent; + char *kbuf = NULL, *pos, *next_line; + ssize_t ret; + + /* Only allow < page size writes at the beginning of the file */ + if ((*ppos != 0) || (count >= PAGE_SIZE)) + return -EINVAL; + + /* Slurp in the user data */ + kbuf = memdup_user_nul(buf, count); + if (IS_ERR(kbuf)) + return PTR_ERR(kbuf); + + /* + * 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); + + memset(&new_map, 0, sizeof(struct uid_gid_map)); + + 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, map_ns, CAP_SYS_ADMIN)) + goto out; + + /* Parse the user data */ + ret = -EINVAL; + pos = kbuf; + for (; pos; pos = next_line) { + + /* 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; + + if ((new_map.nr_extents + 1) == UID_GID_MAP_MAX_EXTENTS && + (next_line != NULL)) + goto out; + + ret = insert_extent(&new_map, &extent); + if (ret < 0) + goto out; + ret = -EINVAL; + } + /* Be very certain 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, map_ns, cap_setid, &new_map)) + goto out; + + ret = -EPERM; + /* Map the lower ids from the parent user namespace to the + * kernel global id space. + */ + for (idx = 0; idx < new_map.nr_extents; idx++) { + struct uid_gid_extent *e; + u32 lower_first; + + if (new_map.nr_extents <= UID_GID_MAP_MAX_BASE_EXTENTS) + e = &new_map.extent[idx]; + else + e = &new_map.forward[idx]; + + lower_first = map_id_range_down(parent_map, + e->lower_first, + e->count); + + /* Fail if we can not map the specified extent to + * the kernel global id space. + */ + if (lower_first == (u32) -1) + goto out; + + e->lower_first = lower_first; + } + + /* + * If we want to use binary search for lookup, this clones the extent + * array and sorts both copies. + */ + ret = sort_idmaps(&new_map); + if (ret < 0) + goto out; + + /* Install the map */ + if (new_map.nr_extents <= UID_GID_MAP_MAX_BASE_EXTENTS) { + memcpy(map->extent, new_map.extent, + new_map.nr_extents * sizeof(new_map.extent[0])); + } else { + map->forward = new_map.forward; + map->reverse = new_map.reverse; + } + smp_wmb(); + map->nr_extents = new_map.nr_extents; + + *ppos = count; + ret = count; +out: + if (ret < 0 && new_map.nr_extents > UID_GID_MAP_MAX_BASE_EXTENTS) { + kfree(new_map.forward); + kfree(new_map.reverse); + map->forward = NULL; + map->reverse = NULL; + map->nr_extents = 0; + } + + mutex_unlock(&userns_state_mutex); + kfree(kbuf); + 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; + + if (cap_setid == CAP_SETUID && !verify_root_map(file, ns, new_map)) + return false; + + /* 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 has the appropriate 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 = READ_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; +} + +/* + * Returns true if @child is the same namespace or a descendant of + * @ancestor. + */ +bool in_userns(const struct user_namespace *ancestor, + const struct user_namespace *child) +{ + const struct user_namespace *ns; + for (ns = child; ns->level > ancestor->level; ns = ns->parent) + ; + return (ns == ancestor); +} + +bool current_in_userns(const struct user_namespace *target_ns) +{ + return in_userns(target_ns, current_user_ns()); +} +EXPORT_SYMBOL(current_in_userns); + +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 nsset *nsset, 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; + + /* Tasks that share a thread group must share a user namespace */ + if (!thread_group_empty(current)) + return -EINVAL; + + if (current->fs->users != 1) + return -EINVAL; + + if (!ns_capable(user_ns, CAP_SYS_ADMIN)) + return -EPERM; + + cred = nsset_cred(nsset); + if (!cred) + return -EINVAL; + + put_user_ns(cred->user_ns); + set_cred_user_ns(cred, get_user_ns(user_ns)); + + if (set_cred_ucounts(cred) < 0) + return -EINVAL; + + return 0; +} + +struct ns_common *ns_get_owner(struct ns_common *ns) +{ + struct user_namespace *my_user_ns = current_user_ns(); + struct user_namespace *owner, *p; + + /* See if the owner is in the current user namespace */ + owner = p = ns->ops->owner(ns); + for (;;) { + if (!p) + return ERR_PTR(-EPERM); + if (p == my_user_ns) + break; + p = p->parent; + } + + return &get_user_ns(owner)->ns; +} + +static struct user_namespace *userns_owner(struct ns_common *ns) +{ + return to_user_ns(ns)->parent; +} + +const struct proc_ns_operations userns_operations = { + .name = "user", + .type = CLONE_NEWUSER, + .get = userns_get, + .put = userns_put, + .install = userns_install, + .owner = userns_owner, + .get_parent = ns_get_owner, +}; + +static __init int user_namespaces_init(void) +{ + user_ns_cachep = KMEM_CACHE(user_namespace, SLAB_PANIC | SLAB_ACCOUNT); + return 0; +} +subsys_initcall(user_namespaces_init); |