2 * This program is free software; you can redistribute it and/or
3 * modify it under the terms of the GNU General Public License as
4 * published by the Free Software Foundation, version 2 of the
8 #include <linux/export.h>
9 #include <linux/nsproxy.h>
10 #include <linux/slab.h>
11 #include <linux/user_namespace.h>
12 #include <linux/proc_fs.h>
13 #include <linux/highuid.h>
14 #include <linux/cred.h>
15 #include <linux/securebits.h>
16 #include <linux/keyctl.h>
17 #include <linux/key-type.h>
18 #include <keys/user-type.h>
19 #include <linux/seq_file.h>
21 #include <linux/uaccess.h>
22 #include <linux/ctype.h>
23 #include <linux/projid.h>
25 static struct kmem_cache *user_ns_cachep __read_mostly;
27 static bool new_idmap_permitted(struct user_namespace *ns, int cap_setid,
28 struct uid_gid_map *map);
30 static void set_cred_user_ns(struct cred *cred, struct user_namespace *user_ns)
32 /* Start with the same capabilities as init but useless for doing
33 * anything as the capabilities are bound to the new user namespace.
35 cred->securebits = SECUREBITS_DEFAULT;
36 cred->cap_inheritable = CAP_EMPTY_SET;
37 cred->cap_permitted = CAP_FULL_SET;
38 cred->cap_effective = CAP_FULL_SET;
39 cred->cap_bset = CAP_FULL_SET;
41 key_put(cred->request_key_auth);
42 cred->request_key_auth = NULL;
44 /* tgcred will be cleared in our caller bc CLONE_THREAD won't be set */
45 cred->user_ns = user_ns;
49 * Create a new user namespace, deriving the creator from the user in the
50 * passed credentials, and replacing that user with the new root user for the
53 * This is called by copy_creds(), which will finish setting the target task's
56 int create_user_ns(struct cred *new)
58 struct user_namespace *ns, *parent_ns = new->user_ns;
59 kuid_t owner = new->euid;
60 kgid_t group = new->egid;
62 /* The creator needs a mapping in the parent user namespace
63 * or else we won't be able to reasonably tell userspace who
64 * created a user_namespace.
66 if (!kuid_has_mapping(parent_ns, owner) ||
67 !kgid_has_mapping(parent_ns, group))
70 ns = kmem_cache_zalloc(user_ns_cachep, GFP_KERNEL);
75 /* Leave the new->user_ns reference with the new user namespace. */
76 ns->parent = parent_ns;
80 set_cred_user_ns(new, ns);
85 int unshare_userns(unsigned long unshare_flags, struct cred **new_cred)
89 if (!(unshare_flags & CLONE_NEWUSER))
92 cred = prepare_creds();
97 return create_user_ns(cred);
100 void free_user_ns(struct kref *kref)
102 struct user_namespace *parent, *ns =
103 container_of(kref, struct user_namespace, kref);
106 kmem_cache_free(user_ns_cachep, ns);
109 EXPORT_SYMBOL(free_user_ns);
111 static u32 map_id_range_down(struct uid_gid_map *map, u32 id, u32 count)
113 unsigned idx, extents;
114 u32 first, last, id2;
116 id2 = id + count - 1;
118 /* Find the matching extent */
119 extents = map->nr_extents;
120 smp_read_barrier_depends();
121 for (idx = 0; idx < extents; idx++) {
122 first = map->extent[idx].first;
123 last = first + map->extent[idx].count - 1;
124 if (id >= first && id <= last &&
125 (id2 >= first && id2 <= last))
128 /* Map the id or note failure */
130 id = (id - first) + map->extent[idx].lower_first;
137 static u32 map_id_down(struct uid_gid_map *map, u32 id)
139 unsigned idx, extents;
142 /* Find the matching extent */
143 extents = map->nr_extents;
144 smp_read_barrier_depends();
145 for (idx = 0; idx < extents; idx++) {
146 first = map->extent[idx].first;
147 last = first + map->extent[idx].count - 1;
148 if (id >= first && id <= last)
151 /* Map the id or note failure */
153 id = (id - first) + map->extent[idx].lower_first;
160 static u32 map_id_up(struct uid_gid_map *map, u32 id)
162 unsigned idx, extents;
165 /* Find the matching extent */
166 extents = map->nr_extents;
167 smp_read_barrier_depends();
168 for (idx = 0; idx < extents; idx++) {
169 first = map->extent[idx].lower_first;
170 last = first + map->extent[idx].count - 1;
171 if (id >= first && id <= last)
174 /* Map the id or note failure */
176 id = (id - first) + map->extent[idx].first;
184 * make_kuid - Map a user-namespace uid pair into a kuid.
185 * @ns: User namespace that the uid is in
186 * @uid: User identifier
188 * Maps a user-namespace uid pair into a kernel internal kuid,
189 * and returns that kuid.
191 * When there is no mapping defined for the user-namespace uid
192 * pair INVALID_UID is returned. Callers are expected to test
193 * for and handle handle INVALID_UID being returned. INVALID_UID
194 * may be tested for using uid_valid().
196 kuid_t make_kuid(struct user_namespace *ns, uid_t uid)
198 /* Map the uid to a global kernel uid */
199 return KUIDT_INIT(map_id_down(&ns->uid_map, uid));
201 EXPORT_SYMBOL(make_kuid);
204 * from_kuid - Create a uid from a kuid user-namespace pair.
205 * @targ: The user namespace we want a uid in.
206 * @kuid: The kernel internal uid to start with.
208 * Map @kuid into the user-namespace specified by @targ and
209 * return the resulting uid.
211 * There is always a mapping into the initial user_namespace.
213 * If @kuid has no mapping in @targ (uid_t)-1 is returned.
215 uid_t from_kuid(struct user_namespace *targ, kuid_t kuid)
217 /* Map the uid from a global kernel uid */
218 return map_id_up(&targ->uid_map, __kuid_val(kuid));
220 EXPORT_SYMBOL(from_kuid);
223 * from_kuid_munged - Create a uid from a kuid user-namespace pair.
224 * @targ: The user namespace we want a uid in.
225 * @kuid: The kernel internal uid to start with.
227 * Map @kuid into the user-namespace specified by @targ and
228 * return the resulting uid.
230 * There is always a mapping into the initial user_namespace.
232 * Unlike from_kuid from_kuid_munged never fails and always
233 * returns a valid uid. This makes from_kuid_munged appropriate
234 * for use in syscalls like stat and getuid where failing the
235 * system call and failing to provide a valid uid are not an
238 * If @kuid has no mapping in @targ overflowuid is returned.
240 uid_t from_kuid_munged(struct user_namespace *targ, kuid_t kuid)
243 uid = from_kuid(targ, kuid);
245 if (uid == (uid_t) -1)
249 EXPORT_SYMBOL(from_kuid_munged);
252 * make_kgid - Map a user-namespace gid pair into a kgid.
253 * @ns: User namespace that the gid is in
254 * @uid: group identifier
256 * Maps a user-namespace gid pair into a kernel internal kgid,
257 * and returns that kgid.
259 * When there is no mapping defined for the user-namespace gid
260 * pair INVALID_GID is returned. Callers are expected to test
261 * for and handle INVALID_GID being returned. INVALID_GID may be
262 * tested for using gid_valid().
264 kgid_t make_kgid(struct user_namespace *ns, gid_t gid)
266 /* Map the gid to a global kernel gid */
267 return KGIDT_INIT(map_id_down(&ns->gid_map, gid));
269 EXPORT_SYMBOL(make_kgid);
272 * from_kgid - Create a gid from a kgid user-namespace pair.
273 * @targ: The user namespace we want a gid in.
274 * @kgid: The kernel internal gid to start with.
276 * Map @kgid into the user-namespace specified by @targ and
277 * return the resulting gid.
279 * There is always a mapping into the initial user_namespace.
281 * If @kgid has no mapping in @targ (gid_t)-1 is returned.
283 gid_t from_kgid(struct user_namespace *targ, kgid_t kgid)
285 /* Map the gid from a global kernel gid */
286 return map_id_up(&targ->gid_map, __kgid_val(kgid));
288 EXPORT_SYMBOL(from_kgid);
291 * from_kgid_munged - Create a gid from a kgid user-namespace pair.
292 * @targ: The user namespace we want a gid in.
293 * @kgid: The kernel internal gid to start with.
295 * Map @kgid into the user-namespace specified by @targ and
296 * return the resulting gid.
298 * There is always a mapping into the initial user_namespace.
300 * Unlike from_kgid from_kgid_munged never fails and always
301 * returns a valid gid. This makes from_kgid_munged appropriate
302 * for use in syscalls like stat and getgid where failing the
303 * system call and failing to provide a valid gid are not options.
305 * If @kgid has no mapping in @targ overflowgid is returned.
307 gid_t from_kgid_munged(struct user_namespace *targ, kgid_t kgid)
310 gid = from_kgid(targ, kgid);
312 if (gid == (gid_t) -1)
316 EXPORT_SYMBOL(from_kgid_munged);
319 * make_kprojid - Map a user-namespace projid pair into a kprojid.
320 * @ns: User namespace that the projid is in
321 * @projid: Project identifier
323 * Maps a user-namespace uid pair into a kernel internal kuid,
324 * and returns that kuid.
326 * When there is no mapping defined for the user-namespace projid
327 * pair INVALID_PROJID is returned. Callers are expected to test
328 * for and handle handle INVALID_PROJID being returned. INVALID_PROJID
329 * may be tested for using projid_valid().
331 kprojid_t make_kprojid(struct user_namespace *ns, projid_t projid)
333 /* Map the uid to a global kernel uid */
334 return KPROJIDT_INIT(map_id_down(&ns->projid_map, projid));
336 EXPORT_SYMBOL(make_kprojid);
339 * from_kprojid - Create a projid from a kprojid user-namespace pair.
340 * @targ: The user namespace we want a projid in.
341 * @kprojid: The kernel internal project identifier to start with.
343 * Map @kprojid into the user-namespace specified by @targ and
344 * return the resulting projid.
346 * There is always a mapping into the initial user_namespace.
348 * If @kprojid has no mapping in @targ (projid_t)-1 is returned.
350 projid_t from_kprojid(struct user_namespace *targ, kprojid_t kprojid)
352 /* Map the uid from a global kernel uid */
353 return map_id_up(&targ->projid_map, __kprojid_val(kprojid));
355 EXPORT_SYMBOL(from_kprojid);
358 * from_kprojid_munged - Create a projiid from a kprojid user-namespace pair.
359 * @targ: The user namespace we want a projid in.
360 * @kprojid: The kernel internal projid to start with.
362 * Map @kprojid into the user-namespace specified by @targ and
363 * return the resulting projid.
365 * There is always a mapping into the initial user_namespace.
367 * Unlike from_kprojid from_kprojid_munged never fails and always
368 * returns a valid projid. This makes from_kprojid_munged
369 * appropriate for use in syscalls like stat and where
370 * failing the system call and failing to provide a valid projid are
373 * If @kprojid has no mapping in @targ OVERFLOW_PROJID is returned.
375 projid_t from_kprojid_munged(struct user_namespace *targ, kprojid_t kprojid)
378 projid = from_kprojid(targ, kprojid);
380 if (projid == (projid_t) -1)
381 projid = OVERFLOW_PROJID;
384 EXPORT_SYMBOL(from_kprojid_munged);
387 static int uid_m_show(struct seq_file *seq, void *v)
389 struct user_namespace *ns = seq->private;
390 struct uid_gid_extent *extent = v;
391 struct user_namespace *lower_ns;
394 lower_ns = current_user_ns();
395 if ((lower_ns == ns) && lower_ns->parent)
396 lower_ns = lower_ns->parent;
398 lower = from_kuid(lower_ns, KUIDT_INIT(extent->lower_first));
400 seq_printf(seq, "%10u %10u %10u\n",
408 static int gid_m_show(struct seq_file *seq, void *v)
410 struct user_namespace *ns = seq->private;
411 struct uid_gid_extent *extent = v;
412 struct user_namespace *lower_ns;
415 lower_ns = current_user_ns();
416 if ((lower_ns == ns) && lower_ns->parent)
417 lower_ns = lower_ns->parent;
419 lower = from_kgid(lower_ns, KGIDT_INIT(extent->lower_first));
421 seq_printf(seq, "%10u %10u %10u\n",
429 static int projid_m_show(struct seq_file *seq, void *v)
431 struct user_namespace *ns = seq->private;
432 struct uid_gid_extent *extent = v;
433 struct user_namespace *lower_ns;
436 lower_ns = seq_user_ns(seq);
437 if ((lower_ns == ns) && lower_ns->parent)
438 lower_ns = lower_ns->parent;
440 lower = from_kprojid(lower_ns, KPROJIDT_INIT(extent->lower_first));
442 seq_printf(seq, "%10u %10u %10u\n",
450 static void *m_start(struct seq_file *seq, loff_t *ppos, struct uid_gid_map *map)
452 struct uid_gid_extent *extent = NULL;
455 if (pos < map->nr_extents)
456 extent = &map->extent[pos];
461 static void *uid_m_start(struct seq_file *seq, loff_t *ppos)
463 struct user_namespace *ns = seq->private;
465 return m_start(seq, ppos, &ns->uid_map);
468 static void *gid_m_start(struct seq_file *seq, loff_t *ppos)
470 struct user_namespace *ns = seq->private;
472 return m_start(seq, ppos, &ns->gid_map);
475 static void *projid_m_start(struct seq_file *seq, loff_t *ppos)
477 struct user_namespace *ns = seq->private;
479 return m_start(seq, ppos, &ns->projid_map);
482 static void *m_next(struct seq_file *seq, void *v, loff_t *pos)
485 return seq->op->start(seq, pos);
488 static void m_stop(struct seq_file *seq, void *v)
493 struct seq_operations proc_uid_seq_operations = {
494 .start = uid_m_start,
500 struct seq_operations proc_gid_seq_operations = {
501 .start = gid_m_start,
507 struct seq_operations proc_projid_seq_operations = {
508 .start = projid_m_start,
511 .show = projid_m_show,
514 static DEFINE_MUTEX(id_map_mutex);
516 static ssize_t map_write(struct file *file, const char __user *buf,
517 size_t count, loff_t *ppos,
519 struct uid_gid_map *map,
520 struct uid_gid_map *parent_map)
522 struct seq_file *seq = file->private_data;
523 struct user_namespace *ns = seq->private;
524 struct uid_gid_map new_map;
526 struct uid_gid_extent *extent, *last = NULL;
527 unsigned long page = 0;
528 char *kbuf, *pos, *next_line;
529 ssize_t ret = -EINVAL;
532 * The id_map_mutex serializes all writes to any given map.
534 * Any map is only ever written once.
536 * An id map fits within 1 cache line on most architectures.
538 * On read nothing needs to be done unless you are on an
539 * architecture with a crazy cache coherency model like alpha.
541 * There is a one time data dependency between reading the
542 * count of the extents and the values of the extents. The
543 * desired behavior is to see the values of the extents that
544 * were written before the count of the extents.
546 * To achieve this smp_wmb() is used on guarantee the write
547 * order and smp_read_barrier_depends() is guaranteed that we
548 * don't have crazy architectures returning stale data.
551 mutex_lock(&id_map_mutex);
554 /* Only allow one successful write to the map */
555 if (map->nr_extents != 0)
558 /* Require the appropriate privilege CAP_SETUID or CAP_SETGID
559 * over the user namespace in order to set the id mapping.
561 if (cap_valid(cap_setid) && !ns_capable(ns, cap_setid))
566 page = __get_free_page(GFP_TEMPORARY);
567 kbuf = (char *) page;
571 /* Only allow <= page size writes at the beginning of the file */
573 if ((*ppos != 0) || (count >= PAGE_SIZE))
576 /* Slurp in the user data */
578 if (copy_from_user(kbuf, buf, count))
582 /* Parse the user data */
585 new_map.nr_extents = 0;
586 for (;pos; pos = next_line) {
587 extent = &new_map.extent[new_map.nr_extents];
589 /* Find the end of line and ensure I don't look past it */
590 next_line = strchr(pos, '\n');
594 if (*next_line == '\0')
598 pos = skip_spaces(pos);
599 extent->first = simple_strtoul(pos, &pos, 10);
603 pos = skip_spaces(pos);
604 extent->lower_first = simple_strtoul(pos, &pos, 10);
608 pos = skip_spaces(pos);
609 extent->count = simple_strtoul(pos, &pos, 10);
610 if (*pos && !isspace(*pos))
613 /* Verify there is not trailing junk on the line */
614 pos = skip_spaces(pos);
618 /* Verify we have been given valid starting values */
619 if ((extent->first == (u32) -1) ||
620 (extent->lower_first == (u32) -1 ))
623 /* Verify count is not zero and does not cause the extent to wrap */
624 if ((extent->first + extent->count) <= extent->first)
626 if ((extent->lower_first + extent->count) <= extent->lower_first)
629 /* For now only accept extents that are strictly in order */
631 (((last->first + last->count) > extent->first) ||
632 ((last->lower_first + last->count) > extent->lower_first)))
635 new_map.nr_extents++;
638 /* Fail if the file contains too many extents */
639 if ((new_map.nr_extents == UID_GID_MAP_MAX_EXTENTS) &&
643 /* Be very certaint the new map actually exists */
644 if (new_map.nr_extents == 0)
648 /* Validate the user is allowed to use user id's mapped to. */
649 if (!new_idmap_permitted(ns, cap_setid, &new_map))
652 /* Map the lower ids from the parent user namespace to the
653 * kernel global id space.
655 for (idx = 0; idx < new_map.nr_extents; idx++) {
657 extent = &new_map.extent[idx];
659 lower_first = map_id_range_down(parent_map,
663 /* Fail if we can not map the specified extent to
664 * the kernel global id space.
666 if (lower_first == (u32) -1)
669 extent->lower_first = lower_first;
672 /* Install the map */
673 memcpy(map->extent, new_map.extent,
674 new_map.nr_extents*sizeof(new_map.extent[0]));
676 map->nr_extents = new_map.nr_extents;
681 mutex_unlock(&id_map_mutex);
687 ssize_t proc_uid_map_write(struct file *file, const char __user *buf, size_t size, loff_t *ppos)
689 struct seq_file *seq = file->private_data;
690 struct user_namespace *ns = seq->private;
695 return map_write(file, buf, size, ppos, CAP_SETUID,
696 &ns->uid_map, &ns->parent->uid_map);
699 ssize_t proc_gid_map_write(struct file *file, const char __user *buf, size_t size, loff_t *ppos)
701 struct seq_file *seq = file->private_data;
702 struct user_namespace *ns = seq->private;
707 return map_write(file, buf, size, ppos, CAP_SETGID,
708 &ns->gid_map, &ns->parent->gid_map);
711 ssize_t proc_projid_map_write(struct file *file, const char __user *buf, size_t size, loff_t *ppos)
713 struct seq_file *seq = file->private_data;
714 struct user_namespace *ns = seq->private;
715 struct user_namespace *seq_ns = seq_user_ns(seq);
720 if ((seq_ns != ns) && (seq_ns != ns->parent))
723 /* Anyone can set any valid project id no capability needed */
724 return map_write(file, buf, size, ppos, -1,
725 &ns->projid_map, &ns->parent->projid_map);
728 static bool new_idmap_permitted(struct user_namespace *ns, int cap_setid,
729 struct uid_gid_map *new_map)
731 /* Allow mapping to your own filesystem ids */
732 if ((new_map->nr_extents == 1) && (new_map->extent[0].count == 1)) {
733 u32 id = new_map->extent[0].lower_first;
734 if (cap_setid == CAP_SETUID) {
735 kuid_t uid = make_kuid(ns->parent, id);
736 if (uid_eq(uid, current_fsuid()))
739 else if (cap_setid == CAP_SETGID) {
740 kgid_t gid = make_kgid(ns->parent, id);
741 if (gid_eq(gid, current_fsgid()))
746 /* Allow anyone to set a mapping that doesn't require privilege */
747 if (!cap_valid(cap_setid))
750 /* Allow the specified ids if we have the appropriate capability
751 * (CAP_SETUID or CAP_SETGID) over the parent user namespace.
753 if (ns_capable(ns->parent, cap_setid))
759 static void *userns_get(struct task_struct *task)
761 struct user_namespace *user_ns;
764 user_ns = get_user_ns(__task_cred(task)->user_ns);
770 static void userns_put(void *ns)
775 static int userns_install(struct nsproxy *nsproxy, void *ns)
777 struct user_namespace *user_ns = ns;
780 /* Don't allow gaining capabilities by reentering
781 * the same user namespace.
783 if (user_ns == current_user_ns())
786 /* Threaded many not enter a different user namespace */
787 if (atomic_read(¤t->mm->mm_users) > 1)
790 if (!ns_capable(user_ns, CAP_SYS_ADMIN))
793 cred = prepare_creds();
797 put_user_ns(cred->user_ns);
798 set_cred_user_ns(cred, get_user_ns(user_ns));
800 return commit_creds(cred);
803 const struct proc_ns_operations userns_operations = {
805 .type = CLONE_NEWUSER,
808 .install = userns_install,
811 static __init int user_namespaces_init(void)
813 user_ns_cachep = KMEM_CACHE(user_namespace, SLAB_PANIC);
816 module_init(user_namespaces_init);