1 // SPDX-License-Identifier: GPL-2.0-only
3 #include <linux/export.h>
4 #include <linux/nsproxy.h>
5 #include <linux/slab.h>
6 #include <linux/sched/signal.h>
7 #include <linux/user_namespace.h>
8 #include <linux/proc_ns.h>
9 #include <linux/highuid.h>
10 #include <linux/cred.h>
11 #include <linux/securebits.h>
12 #include <linux/security.h>
13 #include <linux/keyctl.h>
14 #include <linux/key-type.h>
15 #include <keys/user-type.h>
16 #include <linux/seq_file.h>
18 #include <linux/uaccess.h>
19 #include <linux/ctype.h>
20 #include <linux/projid.h>
21 #include <linux/fs_struct.h>
22 #include <linux/bsearch.h>
23 #include <linux/sort.h>
25 static struct kmem_cache *user_ns_cachep __ro_after_init;
26 static DEFINE_MUTEX(userns_state_mutex);
28 static bool new_idmap_permitted(const struct file *file,
29 struct user_namespace *ns, int cap_setid,
30 struct uid_gid_map *map);
31 static void free_user_ns(struct work_struct *work);
33 static struct ucounts *inc_user_namespaces(struct user_namespace *ns, kuid_t uid)
35 return inc_ucount(ns, uid, UCOUNT_USER_NAMESPACES);
38 static void dec_user_namespaces(struct ucounts *ucounts)
40 return dec_ucount(ucounts, UCOUNT_USER_NAMESPACES);
43 static void set_cred_user_ns(struct cred *cred, struct user_namespace *user_ns)
45 /* Start with the same capabilities as init but useless for doing
46 * anything as the capabilities are bound to the new user namespace.
48 cred->securebits = SECUREBITS_DEFAULT;
49 cred->cap_inheritable = CAP_EMPTY_SET;
50 cred->cap_permitted = CAP_FULL_SET;
51 cred->cap_effective = CAP_FULL_SET;
52 cred->cap_ambient = CAP_EMPTY_SET;
53 cred->cap_bset = CAP_FULL_SET;
55 key_put(cred->request_key_auth);
56 cred->request_key_auth = NULL;
58 /* tgcred will be cleared in our caller bc CLONE_THREAD won't be set */
59 cred->user_ns = user_ns;
62 static unsigned long enforced_nproc_rlimit(void)
64 unsigned long limit = RLIM_INFINITY;
66 /* Is RLIMIT_NPROC currently enforced? */
67 if (!uid_eq(current_uid(), GLOBAL_ROOT_UID) ||
68 (current_user_ns() != &init_user_ns))
69 limit = rlimit(RLIMIT_NPROC);
75 * Create a new user namespace, deriving the creator from the user in the
76 * passed credentials, and replacing that user with the new root user for the
79 * This is called by copy_creds(), which will finish setting the target task's
82 int create_user_ns(struct cred *new)
84 struct user_namespace *ns, *parent_ns = new->user_ns;
85 kuid_t owner = new->euid;
86 kgid_t group = new->egid;
87 struct ucounts *ucounts;
91 if (parent_ns->level > 32)
94 ucounts = inc_user_namespaces(parent_ns, owner);
99 * Verify that we can not violate the policy of which files
100 * may be accessed that is specified by the root directory,
101 * by verifying that the root directory is at the root of the
102 * mount namespace which allows all files to be accessed.
105 if (current_chrooted())
108 /* The creator needs a mapping in the parent user namespace
109 * or else we won't be able to reasonably tell userspace who
110 * created a user_namespace.
113 if (!kuid_has_mapping(parent_ns, owner) ||
114 !kgid_has_mapping(parent_ns, group))
117 ret = security_create_user_ns(new);
122 ns = kmem_cache_zalloc(user_ns_cachep, GFP_KERNEL);
126 ns->parent_could_setfcap = cap_raised(new->cap_effective, CAP_SETFCAP);
127 ret = ns_alloc_inum(&ns->ns);
130 ns->ns.ops = &userns_operations;
132 refcount_set(&ns->ns.count, 1);
133 /* Leave the new->user_ns reference with the new user namespace. */
134 ns->parent = parent_ns;
135 ns->level = parent_ns->level + 1;
138 INIT_WORK(&ns->work, free_user_ns);
139 for (i = 0; i < UCOUNT_COUNTS; i++) {
140 ns->ucount_max[i] = INT_MAX;
142 set_userns_rlimit_max(ns, UCOUNT_RLIMIT_NPROC, enforced_nproc_rlimit());
143 set_userns_rlimit_max(ns, UCOUNT_RLIMIT_MSGQUEUE, rlimit(RLIMIT_MSGQUEUE));
144 set_userns_rlimit_max(ns, UCOUNT_RLIMIT_SIGPENDING, rlimit(RLIMIT_SIGPENDING));
145 set_userns_rlimit_max(ns, UCOUNT_RLIMIT_MEMLOCK, rlimit(RLIMIT_MEMLOCK));
146 ns->ucounts = ucounts;
148 /* Inherit USERNS_SETGROUPS_ALLOWED from our parent */
149 mutex_lock(&userns_state_mutex);
150 ns->flags = parent_ns->flags;
151 mutex_unlock(&userns_state_mutex);
154 INIT_LIST_HEAD(&ns->keyring_name_list);
155 init_rwsem(&ns->keyring_sem);
158 if (!setup_userns_sysctls(ns))
161 set_cred_user_ns(new, ns);
164 #ifdef CONFIG_PERSISTENT_KEYRINGS
165 key_put(ns->persistent_keyring_register);
167 ns_free_inum(&ns->ns);
169 kmem_cache_free(user_ns_cachep, ns);
171 dec_user_namespaces(ucounts);
176 int unshare_userns(unsigned long unshare_flags, struct cred **new_cred)
181 if (!(unshare_flags & CLONE_NEWUSER))
184 cred = prepare_creds();
186 err = create_user_ns(cred);
196 static void free_user_ns(struct work_struct *work)
198 struct user_namespace *parent, *ns =
199 container_of(work, struct user_namespace, work);
202 struct ucounts *ucounts = ns->ucounts;
204 if (ns->gid_map.nr_extents > UID_GID_MAP_MAX_BASE_EXTENTS) {
205 kfree(ns->gid_map.forward);
206 kfree(ns->gid_map.reverse);
208 if (ns->uid_map.nr_extents > UID_GID_MAP_MAX_BASE_EXTENTS) {
209 kfree(ns->uid_map.forward);
210 kfree(ns->uid_map.reverse);
212 if (ns->projid_map.nr_extents > UID_GID_MAP_MAX_BASE_EXTENTS) {
213 kfree(ns->projid_map.forward);
214 kfree(ns->projid_map.reverse);
216 #if IS_ENABLED(CONFIG_BINFMT_MISC)
217 kfree(ns->binfmt_misc);
219 retire_userns_sysctls(ns);
220 key_free_user_ns(ns);
221 ns_free_inum(&ns->ns);
222 kmem_cache_free(user_ns_cachep, ns);
223 dec_user_namespaces(ucounts);
225 } while (refcount_dec_and_test(&parent->ns.count));
228 void __put_user_ns(struct user_namespace *ns)
230 schedule_work(&ns->work);
232 EXPORT_SYMBOL(__put_user_ns);
235 * struct idmap_key - holds the information necessary to find an idmapping in a
236 * sorted idmap array. It is passed to cmp_map_id() as first argument.
239 bool map_up; /* true -> id from kid; false -> kid from id */
240 u32 id; /* id to find */
241 u32 count; /* == 0 unless used with map_id_range_down() */
245 * cmp_map_id - Function to be passed to bsearch() to find the requested
246 * idmapping. Expects struct idmap_key to be passed via @k.
248 static int cmp_map_id(const void *k, const void *e)
250 u32 first, last, id2;
251 const struct idmap_key *key = k;
252 const struct uid_gid_extent *el = e;
254 id2 = key->id + key->count - 1;
256 /* handle map_id_{down,up}() */
258 first = el->lower_first;
262 last = first + el->count - 1;
264 if (key->id >= first && key->id <= last &&
265 (id2 >= first && id2 <= last))
268 if (key->id < first || id2 < first)
275 * map_id_range_down_max - Find idmap via binary search in ordered idmap array.
276 * Can only be called if number of mappings exceeds UID_GID_MAP_MAX_BASE_EXTENTS.
278 static struct uid_gid_extent *
279 map_id_range_down_max(unsigned extents, struct uid_gid_map *map, u32 id, u32 count)
281 struct idmap_key key;
287 return bsearch(&key, map->forward, extents,
288 sizeof(struct uid_gid_extent), cmp_map_id);
292 * map_id_range_down_base - Find idmap via binary search in static extent array.
293 * Can only be called if number of mappings is equal or less than
294 * UID_GID_MAP_MAX_BASE_EXTENTS.
296 static struct uid_gid_extent *
297 map_id_range_down_base(unsigned extents, struct uid_gid_map *map, u32 id, u32 count)
300 u32 first, last, id2;
302 id2 = id + count - 1;
304 /* Find the matching extent */
305 for (idx = 0; idx < extents; idx++) {
306 first = map->extent[idx].first;
307 last = first + map->extent[idx].count - 1;
308 if (id >= first && id <= last &&
309 (id2 >= first && id2 <= last))
310 return &map->extent[idx];
315 static u32 map_id_range_down(struct uid_gid_map *map, u32 id, u32 count)
317 struct uid_gid_extent *extent;
318 unsigned extents = map->nr_extents;
321 if (extents <= UID_GID_MAP_MAX_BASE_EXTENTS)
322 extent = map_id_range_down_base(extents, map, id, count);
324 extent = map_id_range_down_max(extents, map, id, count);
326 /* Map the id or note failure */
328 id = (id - extent->first) + extent->lower_first;
335 u32 map_id_down(struct uid_gid_map *map, u32 id)
337 return map_id_range_down(map, id, 1);
341 * map_id_up_base - Find idmap via binary search in static extent array.
342 * Can only be called if number of mappings is equal or less than
343 * UID_GID_MAP_MAX_BASE_EXTENTS.
345 static struct uid_gid_extent *
346 map_id_up_base(unsigned extents, struct uid_gid_map *map, u32 id)
351 /* Find the matching extent */
352 for (idx = 0; idx < extents; idx++) {
353 first = map->extent[idx].lower_first;
354 last = first + map->extent[idx].count - 1;
355 if (id >= first && id <= last)
356 return &map->extent[idx];
362 * map_id_up_max - Find idmap via binary search in ordered idmap array.
363 * Can only be called if number of mappings exceeds UID_GID_MAP_MAX_BASE_EXTENTS.
365 static struct uid_gid_extent *
366 map_id_up_max(unsigned extents, struct uid_gid_map *map, u32 id)
368 struct idmap_key key;
374 return bsearch(&key, map->reverse, extents,
375 sizeof(struct uid_gid_extent), cmp_map_id);
378 u32 map_id_up(struct uid_gid_map *map, u32 id)
380 struct uid_gid_extent *extent;
381 unsigned extents = map->nr_extents;
384 if (extents <= UID_GID_MAP_MAX_BASE_EXTENTS)
385 extent = map_id_up_base(extents, map, id);
387 extent = map_id_up_max(extents, map, id);
389 /* Map the id or note failure */
391 id = (id - extent->lower_first) + extent->first;
399 * make_kuid - Map a user-namespace uid pair into a kuid.
400 * @ns: User namespace that the uid is in
401 * @uid: User identifier
403 * Maps a user-namespace uid pair into a kernel internal kuid,
404 * and returns that kuid.
406 * When there is no mapping defined for the user-namespace uid
407 * pair INVALID_UID is returned. Callers are expected to test
408 * for and handle INVALID_UID being returned. INVALID_UID
409 * may be tested for using uid_valid().
411 kuid_t make_kuid(struct user_namespace *ns, uid_t uid)
413 /* Map the uid to a global kernel uid */
414 return KUIDT_INIT(map_id_down(&ns->uid_map, uid));
416 EXPORT_SYMBOL(make_kuid);
419 * from_kuid - Create a uid from a kuid user-namespace pair.
420 * @targ: The user namespace we want a uid in.
421 * @kuid: The kernel internal uid to start with.
423 * Map @kuid into the user-namespace specified by @targ and
424 * return the resulting uid.
426 * There is always a mapping into the initial user_namespace.
428 * If @kuid has no mapping in @targ (uid_t)-1 is returned.
430 uid_t from_kuid(struct user_namespace *targ, kuid_t kuid)
432 /* Map the uid from a global kernel uid */
433 return map_id_up(&targ->uid_map, __kuid_val(kuid));
435 EXPORT_SYMBOL(from_kuid);
438 * from_kuid_munged - Create a uid from a kuid user-namespace pair.
439 * @targ: The user namespace we want a uid in.
440 * @kuid: The kernel internal uid to start with.
442 * Map @kuid into the user-namespace specified by @targ and
443 * return the resulting uid.
445 * There is always a mapping into the initial user_namespace.
447 * Unlike from_kuid from_kuid_munged never fails and always
448 * returns a valid uid. This makes from_kuid_munged appropriate
449 * for use in syscalls like stat and getuid where failing the
450 * system call and failing to provide a valid uid are not an
453 * If @kuid has no mapping in @targ overflowuid is returned.
455 uid_t from_kuid_munged(struct user_namespace *targ, kuid_t kuid)
458 uid = from_kuid(targ, kuid);
460 if (uid == (uid_t) -1)
464 EXPORT_SYMBOL(from_kuid_munged);
467 * make_kgid - Map a user-namespace gid pair into a kgid.
468 * @ns: User namespace that the gid is in
469 * @gid: group identifier
471 * Maps a user-namespace gid pair into a kernel internal kgid,
472 * and returns that kgid.
474 * When there is no mapping defined for the user-namespace gid
475 * pair INVALID_GID is returned. Callers are expected to test
476 * for and handle INVALID_GID being returned. INVALID_GID may be
477 * tested for using gid_valid().
479 kgid_t make_kgid(struct user_namespace *ns, gid_t gid)
481 /* Map the gid to a global kernel gid */
482 return KGIDT_INIT(map_id_down(&ns->gid_map, gid));
484 EXPORT_SYMBOL(make_kgid);
487 * from_kgid - Create a gid from a kgid user-namespace pair.
488 * @targ: The user namespace we want a gid in.
489 * @kgid: The kernel internal gid to start with.
491 * Map @kgid into the user-namespace specified by @targ and
492 * return the resulting gid.
494 * There is always a mapping into the initial user_namespace.
496 * If @kgid has no mapping in @targ (gid_t)-1 is returned.
498 gid_t from_kgid(struct user_namespace *targ, kgid_t kgid)
500 /* Map the gid from a global kernel gid */
501 return map_id_up(&targ->gid_map, __kgid_val(kgid));
503 EXPORT_SYMBOL(from_kgid);
506 * from_kgid_munged - Create a gid from a kgid user-namespace pair.
507 * @targ: The user namespace we want a gid in.
508 * @kgid: The kernel internal gid to start with.
510 * Map @kgid into the user-namespace specified by @targ and
511 * return the resulting gid.
513 * There is always a mapping into the initial user_namespace.
515 * Unlike from_kgid from_kgid_munged never fails and always
516 * returns a valid gid. This makes from_kgid_munged appropriate
517 * for use in syscalls like stat and getgid where failing the
518 * system call and failing to provide a valid gid are not options.
520 * If @kgid has no mapping in @targ overflowgid is returned.
522 gid_t from_kgid_munged(struct user_namespace *targ, kgid_t kgid)
525 gid = from_kgid(targ, kgid);
527 if (gid == (gid_t) -1)
531 EXPORT_SYMBOL(from_kgid_munged);
534 * make_kprojid - Map a user-namespace projid pair into a kprojid.
535 * @ns: User namespace that the projid is in
536 * @projid: Project identifier
538 * Maps a user-namespace uid pair into a kernel internal kuid,
539 * and returns that kuid.
541 * When there is no mapping defined for the user-namespace projid
542 * pair INVALID_PROJID is returned. Callers are expected to test
543 * for and handle INVALID_PROJID being returned. INVALID_PROJID
544 * may be tested for using projid_valid().
546 kprojid_t make_kprojid(struct user_namespace *ns, projid_t projid)
548 /* Map the uid to a global kernel uid */
549 return KPROJIDT_INIT(map_id_down(&ns->projid_map, projid));
551 EXPORT_SYMBOL(make_kprojid);
554 * from_kprojid - Create a projid from a kprojid user-namespace pair.
555 * @targ: The user namespace we want a projid in.
556 * @kprojid: The kernel internal project identifier to start with.
558 * Map @kprojid into the user-namespace specified by @targ and
559 * return the resulting projid.
561 * There is always a mapping into the initial user_namespace.
563 * If @kprojid has no mapping in @targ (projid_t)-1 is returned.
565 projid_t from_kprojid(struct user_namespace *targ, kprojid_t kprojid)
567 /* Map the uid from a global kernel uid */
568 return map_id_up(&targ->projid_map, __kprojid_val(kprojid));
570 EXPORT_SYMBOL(from_kprojid);
573 * from_kprojid_munged - Create a projiid from a kprojid user-namespace pair.
574 * @targ: The user namespace we want a projid in.
575 * @kprojid: The kernel internal projid to start with.
577 * Map @kprojid into the user-namespace specified by @targ and
578 * return the resulting projid.
580 * There is always a mapping into the initial user_namespace.
582 * Unlike from_kprojid from_kprojid_munged never fails and always
583 * returns a valid projid. This makes from_kprojid_munged
584 * appropriate for use in syscalls like stat and where
585 * failing the system call and failing to provide a valid projid are
588 * If @kprojid has no mapping in @targ OVERFLOW_PROJID is returned.
590 projid_t from_kprojid_munged(struct user_namespace *targ, kprojid_t kprojid)
593 projid = from_kprojid(targ, kprojid);
595 if (projid == (projid_t) -1)
596 projid = OVERFLOW_PROJID;
599 EXPORT_SYMBOL(from_kprojid_munged);
602 static int uid_m_show(struct seq_file *seq, void *v)
604 struct user_namespace *ns = seq->private;
605 struct uid_gid_extent *extent = v;
606 struct user_namespace *lower_ns;
609 lower_ns = seq_user_ns(seq);
610 if ((lower_ns == ns) && lower_ns->parent)
611 lower_ns = lower_ns->parent;
613 lower = from_kuid(lower_ns, KUIDT_INIT(extent->lower_first));
615 seq_printf(seq, "%10u %10u %10u\n",
623 static int gid_m_show(struct seq_file *seq, void *v)
625 struct user_namespace *ns = seq->private;
626 struct uid_gid_extent *extent = v;
627 struct user_namespace *lower_ns;
630 lower_ns = seq_user_ns(seq);
631 if ((lower_ns == ns) && lower_ns->parent)
632 lower_ns = lower_ns->parent;
634 lower = from_kgid(lower_ns, KGIDT_INIT(extent->lower_first));
636 seq_printf(seq, "%10u %10u %10u\n",
644 static int projid_m_show(struct seq_file *seq, void *v)
646 struct user_namespace *ns = seq->private;
647 struct uid_gid_extent *extent = v;
648 struct user_namespace *lower_ns;
651 lower_ns = seq_user_ns(seq);
652 if ((lower_ns == ns) && lower_ns->parent)
653 lower_ns = lower_ns->parent;
655 lower = from_kprojid(lower_ns, KPROJIDT_INIT(extent->lower_first));
657 seq_printf(seq, "%10u %10u %10u\n",
665 static void *m_start(struct seq_file *seq, loff_t *ppos,
666 struct uid_gid_map *map)
669 unsigned extents = map->nr_extents;
675 if (extents <= UID_GID_MAP_MAX_BASE_EXTENTS)
676 return &map->extent[pos];
678 return &map->forward[pos];
681 static void *uid_m_start(struct seq_file *seq, loff_t *ppos)
683 struct user_namespace *ns = seq->private;
685 return m_start(seq, ppos, &ns->uid_map);
688 static void *gid_m_start(struct seq_file *seq, loff_t *ppos)
690 struct user_namespace *ns = seq->private;
692 return m_start(seq, ppos, &ns->gid_map);
695 static void *projid_m_start(struct seq_file *seq, loff_t *ppos)
697 struct user_namespace *ns = seq->private;
699 return m_start(seq, ppos, &ns->projid_map);
702 static void *m_next(struct seq_file *seq, void *v, loff_t *pos)
705 return seq->op->start(seq, pos);
708 static void m_stop(struct seq_file *seq, void *v)
713 const struct seq_operations proc_uid_seq_operations = {
714 .start = uid_m_start,
720 const struct seq_operations proc_gid_seq_operations = {
721 .start = gid_m_start,
727 const struct seq_operations proc_projid_seq_operations = {
728 .start = projid_m_start,
731 .show = projid_m_show,
734 static bool mappings_overlap(struct uid_gid_map *new_map,
735 struct uid_gid_extent *extent)
737 u32 upper_first, lower_first, upper_last, lower_last;
740 upper_first = extent->first;
741 lower_first = extent->lower_first;
742 upper_last = upper_first + extent->count - 1;
743 lower_last = lower_first + extent->count - 1;
745 for (idx = 0; idx < new_map->nr_extents; idx++) {
746 u32 prev_upper_first, prev_lower_first;
747 u32 prev_upper_last, prev_lower_last;
748 struct uid_gid_extent *prev;
750 if (new_map->nr_extents <= UID_GID_MAP_MAX_BASE_EXTENTS)
751 prev = &new_map->extent[idx];
753 prev = &new_map->forward[idx];
755 prev_upper_first = prev->first;
756 prev_lower_first = prev->lower_first;
757 prev_upper_last = prev_upper_first + prev->count - 1;
758 prev_lower_last = prev_lower_first + prev->count - 1;
760 /* Does the upper range intersect a previous extent? */
761 if ((prev_upper_first <= upper_last) &&
762 (prev_upper_last >= upper_first))
765 /* Does the lower range intersect a previous extent? */
766 if ((prev_lower_first <= lower_last) &&
767 (prev_lower_last >= lower_first))
774 * insert_extent - Safely insert a new idmap extent into struct uid_gid_map.
775 * Takes care to allocate a 4K block of memory if the number of mappings exceeds
776 * UID_GID_MAP_MAX_BASE_EXTENTS.
778 static int insert_extent(struct uid_gid_map *map, struct uid_gid_extent *extent)
780 struct uid_gid_extent *dest;
782 if (map->nr_extents == UID_GID_MAP_MAX_BASE_EXTENTS) {
783 struct uid_gid_extent *forward;
785 /* Allocate memory for 340 mappings. */
786 forward = kmalloc_array(UID_GID_MAP_MAX_EXTENTS,
787 sizeof(struct uid_gid_extent),
792 /* Copy over memory. Only set up memory for the forward pointer.
793 * Defer the memory setup for the reverse pointer.
795 memcpy(forward, map->extent,
796 map->nr_extents * sizeof(map->extent[0]));
798 map->forward = forward;
802 if (map->nr_extents < UID_GID_MAP_MAX_BASE_EXTENTS)
803 dest = &map->extent[map->nr_extents];
805 dest = &map->forward[map->nr_extents];
812 /* cmp function to sort() forward mappings */
813 static int cmp_extents_forward(const void *a, const void *b)
815 const struct uid_gid_extent *e1 = a;
816 const struct uid_gid_extent *e2 = b;
818 if (e1->first < e2->first)
821 if (e1->first > e2->first)
827 /* cmp function to sort() reverse mappings */
828 static int cmp_extents_reverse(const void *a, const void *b)
830 const struct uid_gid_extent *e1 = a;
831 const struct uid_gid_extent *e2 = b;
833 if (e1->lower_first < e2->lower_first)
836 if (e1->lower_first > e2->lower_first)
843 * sort_idmaps - Sorts an array of idmap entries.
844 * Can only be called if number of mappings exceeds UID_GID_MAP_MAX_BASE_EXTENTS.
846 static int sort_idmaps(struct uid_gid_map *map)
848 if (map->nr_extents <= UID_GID_MAP_MAX_BASE_EXTENTS)
851 /* Sort forward array. */
852 sort(map->forward, map->nr_extents, sizeof(struct uid_gid_extent),
853 cmp_extents_forward, NULL);
855 /* Only copy the memory from forward we actually need. */
856 map->reverse = kmemdup(map->forward,
857 map->nr_extents * sizeof(struct uid_gid_extent),
862 /* Sort reverse array. */
863 sort(map->reverse, map->nr_extents, sizeof(struct uid_gid_extent),
864 cmp_extents_reverse, NULL);
870 * verify_root_map() - check the uid 0 mapping
871 * @file: idmapping file
872 * @map_ns: user namespace of the target process
873 * @new_map: requested idmap
875 * If a process requests mapping parent uid 0 into the new ns, verify that the
876 * process writing the map had the CAP_SETFCAP capability as the target process
877 * will be able to write fscaps that are valid in ancestor user namespaces.
879 * Return: true if the mapping is allowed, false if not.
881 static bool verify_root_map(const struct file *file,
882 struct user_namespace *map_ns,
883 struct uid_gid_map *new_map)
886 const struct user_namespace *file_ns = file->f_cred->user_ns;
887 struct uid_gid_extent *extent0 = NULL;
889 for (idx = 0; idx < new_map->nr_extents; idx++) {
890 if (new_map->nr_extents <= UID_GID_MAP_MAX_BASE_EXTENTS)
891 extent0 = &new_map->extent[idx];
893 extent0 = &new_map->forward[idx];
894 if (extent0->lower_first == 0)
903 if (map_ns == file_ns) {
904 /* The process unshared its ns and is writing to its own
905 * /proc/self/uid_map. User already has full capabilites in
906 * the new namespace. Verify that the parent had CAP_SETFCAP
909 if (!file_ns->parent_could_setfcap)
912 /* Process p1 is writing to uid_map of p2, who is in a child
913 * user namespace to p1's. Verify that the opener of the map
914 * file has CAP_SETFCAP against the parent of the new map
916 if (!file_ns_capable(file, map_ns->parent, CAP_SETFCAP))
923 static ssize_t map_write(struct file *file, const char __user *buf,
924 size_t count, loff_t *ppos,
926 struct uid_gid_map *map,
927 struct uid_gid_map *parent_map)
929 struct seq_file *seq = file->private_data;
930 struct user_namespace *map_ns = seq->private;
931 struct uid_gid_map new_map;
933 struct uid_gid_extent extent;
934 char *kbuf, *pos, *next_line;
937 /* Only allow < page size writes at the beginning of the file */
938 if ((*ppos != 0) || (count >= PAGE_SIZE))
941 /* Slurp in the user data */
942 kbuf = memdup_user_nul(buf, count);
944 return PTR_ERR(kbuf);
947 * The userns_state_mutex serializes all writes to any given map.
949 * Any map is only ever written once.
951 * An id map fits within 1 cache line on most architectures.
953 * On read nothing needs to be done unless you are on an
954 * architecture with a crazy cache coherency model like alpha.
956 * There is a one time data dependency between reading the
957 * count of the extents and the values of the extents. The
958 * desired behavior is to see the values of the extents that
959 * were written before the count of the extents.
961 * To achieve this smp_wmb() is used on guarantee the write
962 * order and smp_rmb() is guaranteed that we don't have crazy
963 * architectures returning stale data.
965 mutex_lock(&userns_state_mutex);
967 memset(&new_map, 0, sizeof(struct uid_gid_map));
970 /* Only allow one successful write to the map */
971 if (map->nr_extents != 0)
975 * Adjusting namespace settings requires capabilities on the target.
977 if (cap_valid(cap_setid) && !file_ns_capable(file, map_ns, CAP_SYS_ADMIN))
980 /* Parse the user data */
983 for (; pos; pos = next_line) {
985 /* Find the end of line and ensure I don't look past it */
986 next_line = strchr(pos, '\n');
990 if (*next_line == '\0')
994 pos = skip_spaces(pos);
995 extent.first = simple_strtoul(pos, &pos, 10);
999 pos = skip_spaces(pos);
1000 extent.lower_first = simple_strtoul(pos, &pos, 10);
1004 pos = skip_spaces(pos);
1005 extent.count = simple_strtoul(pos, &pos, 10);
1006 if (*pos && !isspace(*pos))
1009 /* Verify there is not trailing junk on the line */
1010 pos = skip_spaces(pos);
1014 /* Verify we have been given valid starting values */
1015 if ((extent.first == (u32) -1) ||
1016 (extent.lower_first == (u32) -1))
1019 /* Verify count is not zero and does not cause the
1022 if ((extent.first + extent.count) <= extent.first)
1024 if ((extent.lower_first + extent.count) <=
1028 /* Do the ranges in extent overlap any previous extents? */
1029 if (mappings_overlap(&new_map, &extent))
1032 if ((new_map.nr_extents + 1) == UID_GID_MAP_MAX_EXTENTS &&
1033 (next_line != NULL))
1036 ret = insert_extent(&new_map, &extent);
1041 /* Be very certain the new map actually exists */
1042 if (new_map.nr_extents == 0)
1046 /* Validate the user is allowed to use user id's mapped to. */
1047 if (!new_idmap_permitted(file, map_ns, cap_setid, &new_map))
1051 /* Map the lower ids from the parent user namespace to the
1052 * kernel global id space.
1054 for (idx = 0; idx < new_map.nr_extents; idx++) {
1055 struct uid_gid_extent *e;
1058 if (new_map.nr_extents <= UID_GID_MAP_MAX_BASE_EXTENTS)
1059 e = &new_map.extent[idx];
1061 e = &new_map.forward[idx];
1063 lower_first = map_id_range_down(parent_map,
1067 /* Fail if we can not map the specified extent to
1068 * the kernel global id space.
1070 if (lower_first == (u32) -1)
1073 e->lower_first = lower_first;
1077 * If we want to use binary search for lookup, this clones the extent
1078 * array and sorts both copies.
1080 ret = sort_idmaps(&new_map);
1084 /* Install the map */
1085 if (new_map.nr_extents <= UID_GID_MAP_MAX_BASE_EXTENTS) {
1086 memcpy(map->extent, new_map.extent,
1087 new_map.nr_extents * sizeof(new_map.extent[0]));
1089 map->forward = new_map.forward;
1090 map->reverse = new_map.reverse;
1093 map->nr_extents = new_map.nr_extents;
1098 if (ret < 0 && new_map.nr_extents > UID_GID_MAP_MAX_BASE_EXTENTS) {
1099 kfree(new_map.forward);
1100 kfree(new_map.reverse);
1101 map->forward = NULL;
1102 map->reverse = NULL;
1103 map->nr_extents = 0;
1106 mutex_unlock(&userns_state_mutex);
1111 ssize_t proc_uid_map_write(struct file *file, const char __user *buf,
1112 size_t size, loff_t *ppos)
1114 struct seq_file *seq = file->private_data;
1115 struct user_namespace *ns = seq->private;
1116 struct user_namespace *seq_ns = seq_user_ns(seq);
1121 if ((seq_ns != ns) && (seq_ns != ns->parent))
1124 return map_write(file, buf, size, ppos, CAP_SETUID,
1125 &ns->uid_map, &ns->parent->uid_map);
1128 ssize_t proc_gid_map_write(struct file *file, const char __user *buf,
1129 size_t size, loff_t *ppos)
1131 struct seq_file *seq = file->private_data;
1132 struct user_namespace *ns = seq->private;
1133 struct user_namespace *seq_ns = seq_user_ns(seq);
1138 if ((seq_ns != ns) && (seq_ns != ns->parent))
1141 return map_write(file, buf, size, ppos, CAP_SETGID,
1142 &ns->gid_map, &ns->parent->gid_map);
1145 ssize_t proc_projid_map_write(struct file *file, const char __user *buf,
1146 size_t size, loff_t *ppos)
1148 struct seq_file *seq = file->private_data;
1149 struct user_namespace *ns = seq->private;
1150 struct user_namespace *seq_ns = seq_user_ns(seq);
1155 if ((seq_ns != ns) && (seq_ns != ns->parent))
1158 /* Anyone can set any valid project id no capability needed */
1159 return map_write(file, buf, size, ppos, -1,
1160 &ns->projid_map, &ns->parent->projid_map);
1163 static bool new_idmap_permitted(const struct file *file,
1164 struct user_namespace *ns, int cap_setid,
1165 struct uid_gid_map *new_map)
1167 const struct cred *cred = file->f_cred;
1169 if (cap_setid == CAP_SETUID && !verify_root_map(file, ns, new_map))
1172 /* Don't allow mappings that would allow anything that wouldn't
1173 * be allowed without the establishment of unprivileged mappings.
1175 if ((new_map->nr_extents == 1) && (new_map->extent[0].count == 1) &&
1176 uid_eq(ns->owner, cred->euid)) {
1177 u32 id = new_map->extent[0].lower_first;
1178 if (cap_setid == CAP_SETUID) {
1179 kuid_t uid = make_kuid(ns->parent, id);
1180 if (uid_eq(uid, cred->euid))
1182 } else if (cap_setid == CAP_SETGID) {
1183 kgid_t gid = make_kgid(ns->parent, id);
1184 if (!(ns->flags & USERNS_SETGROUPS_ALLOWED) &&
1185 gid_eq(gid, cred->egid))
1190 /* Allow anyone to set a mapping that doesn't require privilege */
1191 if (!cap_valid(cap_setid))
1194 /* Allow the specified ids if we have the appropriate capability
1195 * (CAP_SETUID or CAP_SETGID) over the parent user namespace.
1196 * And the opener of the id file also has the appropriate capability.
1198 if (ns_capable(ns->parent, cap_setid) &&
1199 file_ns_capable(file, ns->parent, cap_setid))
1205 int proc_setgroups_show(struct seq_file *seq, void *v)
1207 struct user_namespace *ns = seq->private;
1208 unsigned long userns_flags = READ_ONCE(ns->flags);
1210 seq_printf(seq, "%s\n",
1211 (userns_flags & USERNS_SETGROUPS_ALLOWED) ?
1216 ssize_t proc_setgroups_write(struct file *file, const char __user *buf,
1217 size_t count, loff_t *ppos)
1219 struct seq_file *seq = file->private_data;
1220 struct user_namespace *ns = seq->private;
1222 bool setgroups_allowed;
1225 /* Only allow a very narrow range of strings to be written */
1227 if ((*ppos != 0) || (count >= sizeof(kbuf)))
1230 /* What was written? */
1232 if (copy_from_user(kbuf, buf, count))
1237 /* What is being requested? */
1239 if (strncmp(pos, "allow", 5) == 0) {
1241 setgroups_allowed = true;
1243 else if (strncmp(pos, "deny", 4) == 0) {
1245 setgroups_allowed = false;
1250 /* Verify there is not trailing junk on the line */
1251 pos = skip_spaces(pos);
1256 mutex_lock(&userns_state_mutex);
1257 if (setgroups_allowed) {
1258 /* Enabling setgroups after setgroups has been disabled
1261 if (!(ns->flags & USERNS_SETGROUPS_ALLOWED))
1264 /* Permanently disabling setgroups after setgroups has
1265 * been enabled by writing the gid_map is not allowed.
1267 if (ns->gid_map.nr_extents != 0)
1269 ns->flags &= ~USERNS_SETGROUPS_ALLOWED;
1271 mutex_unlock(&userns_state_mutex);
1273 /* Report a successful write */
1279 mutex_unlock(&userns_state_mutex);
1283 bool userns_may_setgroups(const struct user_namespace *ns)
1287 mutex_lock(&userns_state_mutex);
1288 /* It is not safe to use setgroups until a gid mapping in
1289 * the user namespace has been established.
1291 allowed = ns->gid_map.nr_extents != 0;
1292 /* Is setgroups allowed? */
1293 allowed = allowed && (ns->flags & USERNS_SETGROUPS_ALLOWED);
1294 mutex_unlock(&userns_state_mutex);
1300 * Returns true if @child is the same namespace or a descendant of
1303 bool in_userns(const struct user_namespace *ancestor,
1304 const struct user_namespace *child)
1306 const struct user_namespace *ns;
1307 for (ns = child; ns->level > ancestor->level; ns = ns->parent)
1309 return (ns == ancestor);
1312 bool current_in_userns(const struct user_namespace *target_ns)
1314 return in_userns(target_ns, current_user_ns());
1316 EXPORT_SYMBOL(current_in_userns);
1318 static inline struct user_namespace *to_user_ns(struct ns_common *ns)
1320 return container_of(ns, struct user_namespace, ns);
1323 static struct ns_common *userns_get(struct task_struct *task)
1325 struct user_namespace *user_ns;
1328 user_ns = get_user_ns(__task_cred(task)->user_ns);
1331 return user_ns ? &user_ns->ns : NULL;
1334 static void userns_put(struct ns_common *ns)
1336 put_user_ns(to_user_ns(ns));
1339 static int userns_install(struct nsset *nsset, struct ns_common *ns)
1341 struct user_namespace *user_ns = to_user_ns(ns);
1344 /* Don't allow gaining capabilities by reentering
1345 * the same user namespace.
1347 if (user_ns == current_user_ns())
1350 /* Tasks that share a thread group must share a user namespace */
1351 if (!thread_group_empty(current))
1354 if (current->fs->users != 1)
1357 if (!ns_capable(user_ns, CAP_SYS_ADMIN))
1360 cred = nsset_cred(nsset);
1364 put_user_ns(cred->user_ns);
1365 set_cred_user_ns(cred, get_user_ns(user_ns));
1367 if (set_cred_ucounts(cred) < 0)
1373 struct ns_common *ns_get_owner(struct ns_common *ns)
1375 struct user_namespace *my_user_ns = current_user_ns();
1376 struct user_namespace *owner, *p;
1378 /* See if the owner is in the current user namespace */
1379 owner = p = ns->ops->owner(ns);
1382 return ERR_PTR(-EPERM);
1383 if (p == my_user_ns)
1388 return &get_user_ns(owner)->ns;
1391 static struct user_namespace *userns_owner(struct ns_common *ns)
1393 return to_user_ns(ns)->parent;
1396 const struct proc_ns_operations userns_operations = {
1398 .type = CLONE_NEWUSER,
1401 .install = userns_install,
1402 .owner = userns_owner,
1403 .get_parent = ns_get_owner,
1406 static __init int user_namespaces_init(void)
1408 user_ns_cachep = KMEM_CACHE(user_namespace, SLAB_PANIC | SLAB_ACCOUNT);
1411 subsys_initcall(user_namespaces_init);