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_ns.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>
24 #include <linux/fs_struct.h>
26 static struct kmem_cache
*user_ns_cachep __read_mostly
;
28 static bool new_idmap_permitted(const struct file
*file
,
29 struct user_namespace
*ns
, int cap_setid
,
30 struct uid_gid_map
*map
);
32 static void set_cred_user_ns(struct cred
*cred
, struct user_namespace
*user_ns
)
34 /* Start with the same capabilities as init but useless for doing
35 * anything as the capabilities are bound to the new user namespace.
37 cred
->securebits
= SECUREBITS_DEFAULT
;
38 cred
->cap_inheritable
= CAP_EMPTY_SET
;
39 cred
->cap_permitted
= CAP_FULL_SET
;
40 cred
->cap_effective
= CAP_FULL_SET
;
41 cred
->cap_bset
= CAP_FULL_SET
;
43 key_put(cred
->request_key_auth
);
44 cred
->request_key_auth
= NULL
;
46 /* tgcred will be cleared in our caller bc CLONE_THREAD won't be set */
47 cred
->user_ns
= user_ns
;
51 * Create a new user namespace, deriving the creator from the user in the
52 * passed credentials, and replacing that user with the new root user for the
55 * This is called by copy_creds(), which will finish setting the target task's
58 int create_user_ns(struct cred
*new)
60 struct user_namespace
*ns
, *parent_ns
= new->user_ns
;
61 kuid_t owner
= new->euid
;
62 kgid_t group
= new->egid
;
65 if (parent_ns
->level
> 32)
69 * Verify that we can not violate the policy of which files
70 * may be accessed that is specified by the root directory,
71 * by verifing that the root directory is at the root of the
72 * mount namespace which allows all files to be accessed.
74 if (current_chrooted())
77 /* The creator needs a mapping in the parent user namespace
78 * or else we won't be able to reasonably tell userspace who
79 * created a user_namespace.
81 if (!kuid_has_mapping(parent_ns
, owner
) ||
82 !kgid_has_mapping(parent_ns
, group
))
85 ns
= kmem_cache_zalloc(user_ns_cachep
, GFP_KERNEL
);
89 ret
= ns_alloc_inum(&ns
->ns
);
91 kmem_cache_free(user_ns_cachep
, ns
);
94 ns
->ns
.ops
= &userns_operations
;
96 atomic_set(&ns
->count
, 1);
97 /* Leave the new->user_ns reference with the new user namespace. */
98 ns
->parent
= parent_ns
;
99 ns
->level
= parent_ns
->level
+ 1;
103 set_cred_user_ns(new, ns
);
105 #ifdef CONFIG_PERSISTENT_KEYRINGS
106 init_rwsem(&ns
->persistent_keyring_register_sem
);
111 int unshare_userns(unsigned long unshare_flags
, struct cred
**new_cred
)
116 if (!(unshare_flags
& CLONE_NEWUSER
))
119 cred
= prepare_creds();
121 err
= create_user_ns(cred
);
131 void free_user_ns(struct user_namespace
*ns
)
133 struct user_namespace
*parent
;
137 #ifdef CONFIG_PERSISTENT_KEYRINGS
138 key_put(ns
->persistent_keyring_register
);
140 ns_free_inum(&ns
->ns
);
141 kmem_cache_free(user_ns_cachep
, ns
);
143 } while (atomic_dec_and_test(&parent
->count
));
145 EXPORT_SYMBOL(free_user_ns
);
147 static u32
map_id_range_down(struct uid_gid_map
*map
, u32 id
, u32 count
)
149 unsigned idx
, extents
;
150 u32 first
, last
, id2
;
152 id2
= id
+ count
- 1;
154 /* Find the matching extent */
155 extents
= map
->nr_extents
;
157 for (idx
= 0; idx
< extents
; idx
++) {
158 first
= map
->extent
[idx
].first
;
159 last
= first
+ map
->extent
[idx
].count
- 1;
160 if (id
>= first
&& id
<= last
&&
161 (id2
>= first
&& id2
<= last
))
164 /* Map the id or note failure */
166 id
= (id
- first
) + map
->extent
[idx
].lower_first
;
173 static u32
map_id_down(struct uid_gid_map
*map
, u32 id
)
175 unsigned idx
, extents
;
178 /* Find the matching extent */
179 extents
= map
->nr_extents
;
181 for (idx
= 0; idx
< extents
; idx
++) {
182 first
= map
->extent
[idx
].first
;
183 last
= first
+ map
->extent
[idx
].count
- 1;
184 if (id
>= first
&& id
<= last
)
187 /* Map the id or note failure */
189 id
= (id
- first
) + map
->extent
[idx
].lower_first
;
196 static u32
map_id_up(struct uid_gid_map
*map
, u32 id
)
198 unsigned idx
, extents
;
201 /* Find the matching extent */
202 extents
= map
->nr_extents
;
204 for (idx
= 0; idx
< extents
; idx
++) {
205 first
= map
->extent
[idx
].lower_first
;
206 last
= first
+ map
->extent
[idx
].count
- 1;
207 if (id
>= first
&& id
<= last
)
210 /* Map the id or note failure */
212 id
= (id
- first
) + map
->extent
[idx
].first
;
220 * make_kuid - Map a user-namespace uid pair into a kuid.
221 * @ns: User namespace that the uid is in
222 * @uid: User identifier
224 * Maps a user-namespace uid pair into a kernel internal kuid,
225 * and returns that kuid.
227 * When there is no mapping defined for the user-namespace uid
228 * pair INVALID_UID is returned. Callers are expected to test
229 * for and handle INVALID_UID being returned. INVALID_UID
230 * may be tested for using uid_valid().
232 kuid_t
make_kuid(struct user_namespace
*ns
, uid_t uid
)
234 /* Map the uid to a global kernel uid */
235 return KUIDT_INIT(map_id_down(&ns
->uid_map
, uid
));
237 EXPORT_SYMBOL(make_kuid
);
240 * from_kuid - Create a uid from a kuid user-namespace pair.
241 * @targ: The user namespace we want a uid in.
242 * @kuid: The kernel internal uid to start with.
244 * Map @kuid into the user-namespace specified by @targ and
245 * return the resulting uid.
247 * There is always a mapping into the initial user_namespace.
249 * If @kuid has no mapping in @targ (uid_t)-1 is returned.
251 uid_t
from_kuid(struct user_namespace
*targ
, kuid_t kuid
)
253 /* Map the uid from a global kernel uid */
254 return map_id_up(&targ
->uid_map
, __kuid_val(kuid
));
256 EXPORT_SYMBOL(from_kuid
);
259 * from_kuid_munged - Create a uid from a kuid user-namespace pair.
260 * @targ: The user namespace we want a uid in.
261 * @kuid: The kernel internal uid to start with.
263 * Map @kuid into the user-namespace specified by @targ and
264 * return the resulting uid.
266 * There is always a mapping into the initial user_namespace.
268 * Unlike from_kuid from_kuid_munged never fails and always
269 * returns a valid uid. This makes from_kuid_munged appropriate
270 * for use in syscalls like stat and getuid where failing the
271 * system call and failing to provide a valid uid are not an
274 * If @kuid has no mapping in @targ overflowuid is returned.
276 uid_t
from_kuid_munged(struct user_namespace
*targ
, kuid_t kuid
)
279 uid
= from_kuid(targ
, kuid
);
281 if (uid
== (uid_t
) -1)
285 EXPORT_SYMBOL(from_kuid_munged
);
288 * make_kgid - Map a user-namespace gid pair into a kgid.
289 * @ns: User namespace that the gid is in
290 * @gid: group identifier
292 * Maps a user-namespace gid pair into a kernel internal kgid,
293 * and returns that kgid.
295 * When there is no mapping defined for the user-namespace gid
296 * pair INVALID_GID is returned. Callers are expected to test
297 * for and handle INVALID_GID being returned. INVALID_GID may be
298 * tested for using gid_valid().
300 kgid_t
make_kgid(struct user_namespace
*ns
, gid_t gid
)
302 /* Map the gid to a global kernel gid */
303 return KGIDT_INIT(map_id_down(&ns
->gid_map
, gid
));
305 EXPORT_SYMBOL(make_kgid
);
308 * from_kgid - Create a gid from a kgid user-namespace pair.
309 * @targ: The user namespace we want a gid in.
310 * @kgid: The kernel internal gid to start with.
312 * Map @kgid into the user-namespace specified by @targ and
313 * return the resulting gid.
315 * There is always a mapping into the initial user_namespace.
317 * If @kgid has no mapping in @targ (gid_t)-1 is returned.
319 gid_t
from_kgid(struct user_namespace
*targ
, kgid_t kgid
)
321 /* Map the gid from a global kernel gid */
322 return map_id_up(&targ
->gid_map
, __kgid_val(kgid
));
324 EXPORT_SYMBOL(from_kgid
);
327 * from_kgid_munged - Create a gid from a kgid user-namespace pair.
328 * @targ: The user namespace we want a gid in.
329 * @kgid: The kernel internal gid to start with.
331 * Map @kgid into the user-namespace specified by @targ and
332 * return the resulting gid.
334 * There is always a mapping into the initial user_namespace.
336 * Unlike from_kgid from_kgid_munged never fails and always
337 * returns a valid gid. This makes from_kgid_munged appropriate
338 * for use in syscalls like stat and getgid where failing the
339 * system call and failing to provide a valid gid are not options.
341 * If @kgid has no mapping in @targ overflowgid is returned.
343 gid_t
from_kgid_munged(struct user_namespace
*targ
, kgid_t kgid
)
346 gid
= from_kgid(targ
, kgid
);
348 if (gid
== (gid_t
) -1)
352 EXPORT_SYMBOL(from_kgid_munged
);
355 * make_kprojid - Map a user-namespace projid pair into a kprojid.
356 * @ns: User namespace that the projid is in
357 * @projid: Project identifier
359 * Maps a user-namespace uid pair into a kernel internal kuid,
360 * and returns that kuid.
362 * When there is no mapping defined for the user-namespace projid
363 * pair INVALID_PROJID is returned. Callers are expected to test
364 * for and handle handle INVALID_PROJID being returned. INVALID_PROJID
365 * may be tested for using projid_valid().
367 kprojid_t
make_kprojid(struct user_namespace
*ns
, projid_t projid
)
369 /* Map the uid to a global kernel uid */
370 return KPROJIDT_INIT(map_id_down(&ns
->projid_map
, projid
));
372 EXPORT_SYMBOL(make_kprojid
);
375 * from_kprojid - Create a projid from a kprojid user-namespace pair.
376 * @targ: The user namespace we want a projid in.
377 * @kprojid: The kernel internal project identifier to start with.
379 * Map @kprojid into the user-namespace specified by @targ and
380 * return the resulting projid.
382 * There is always a mapping into the initial user_namespace.
384 * If @kprojid has no mapping in @targ (projid_t)-1 is returned.
386 projid_t
from_kprojid(struct user_namespace
*targ
, kprojid_t kprojid
)
388 /* Map the uid from a global kernel uid */
389 return map_id_up(&targ
->projid_map
, __kprojid_val(kprojid
));
391 EXPORT_SYMBOL(from_kprojid
);
394 * from_kprojid_munged - Create a projiid from a kprojid user-namespace pair.
395 * @targ: The user namespace we want a projid in.
396 * @kprojid: The kernel internal projid to start with.
398 * Map @kprojid into the user-namespace specified by @targ and
399 * return the resulting projid.
401 * There is always a mapping into the initial user_namespace.
403 * Unlike from_kprojid from_kprojid_munged never fails and always
404 * returns a valid projid. This makes from_kprojid_munged
405 * appropriate for use in syscalls like stat and where
406 * failing the system call and failing to provide a valid projid are
409 * If @kprojid has no mapping in @targ OVERFLOW_PROJID is returned.
411 projid_t
from_kprojid_munged(struct user_namespace
*targ
, kprojid_t kprojid
)
414 projid
= from_kprojid(targ
, kprojid
);
416 if (projid
== (projid_t
) -1)
417 projid
= OVERFLOW_PROJID
;
420 EXPORT_SYMBOL(from_kprojid_munged
);
423 static int uid_m_show(struct seq_file
*seq
, void *v
)
425 struct user_namespace
*ns
= seq
->private;
426 struct uid_gid_extent
*extent
= v
;
427 struct user_namespace
*lower_ns
;
430 lower_ns
= seq_user_ns(seq
);
431 if ((lower_ns
== ns
) && lower_ns
->parent
)
432 lower_ns
= lower_ns
->parent
;
434 lower
= from_kuid(lower_ns
, KUIDT_INIT(extent
->lower_first
));
436 seq_printf(seq
, "%10u %10u %10u\n",
444 static int gid_m_show(struct seq_file
*seq
, void *v
)
446 struct user_namespace
*ns
= seq
->private;
447 struct uid_gid_extent
*extent
= v
;
448 struct user_namespace
*lower_ns
;
451 lower_ns
= seq_user_ns(seq
);
452 if ((lower_ns
== ns
) && lower_ns
->parent
)
453 lower_ns
= lower_ns
->parent
;
455 lower
= from_kgid(lower_ns
, KGIDT_INIT(extent
->lower_first
));
457 seq_printf(seq
, "%10u %10u %10u\n",
465 static int projid_m_show(struct seq_file
*seq
, void *v
)
467 struct user_namespace
*ns
= seq
->private;
468 struct uid_gid_extent
*extent
= v
;
469 struct user_namespace
*lower_ns
;
472 lower_ns
= seq_user_ns(seq
);
473 if ((lower_ns
== ns
) && lower_ns
->parent
)
474 lower_ns
= lower_ns
->parent
;
476 lower
= from_kprojid(lower_ns
, KPROJIDT_INIT(extent
->lower_first
));
478 seq_printf(seq
, "%10u %10u %10u\n",
486 static void *m_start(struct seq_file
*seq
, loff_t
*ppos
,
487 struct uid_gid_map
*map
)
489 struct uid_gid_extent
*extent
= NULL
;
492 if (pos
< map
->nr_extents
)
493 extent
= &map
->extent
[pos
];
498 static void *uid_m_start(struct seq_file
*seq
, loff_t
*ppos
)
500 struct user_namespace
*ns
= seq
->private;
502 return m_start(seq
, ppos
, &ns
->uid_map
);
505 static void *gid_m_start(struct seq_file
*seq
, loff_t
*ppos
)
507 struct user_namespace
*ns
= seq
->private;
509 return m_start(seq
, ppos
, &ns
->gid_map
);
512 static void *projid_m_start(struct seq_file
*seq
, loff_t
*ppos
)
514 struct user_namespace
*ns
= seq
->private;
516 return m_start(seq
, ppos
, &ns
->projid_map
);
519 static void *m_next(struct seq_file
*seq
, void *v
, loff_t
*pos
)
522 return seq
->op
->start(seq
, pos
);
525 static void m_stop(struct seq_file
*seq
, void *v
)
530 const struct seq_operations proc_uid_seq_operations
= {
531 .start
= uid_m_start
,
537 const struct seq_operations proc_gid_seq_operations
= {
538 .start
= gid_m_start
,
544 const struct seq_operations proc_projid_seq_operations
= {
545 .start
= projid_m_start
,
548 .show
= projid_m_show
,
551 static bool mappings_overlap(struct uid_gid_map
*new_map
,
552 struct uid_gid_extent
*extent
)
554 u32 upper_first
, lower_first
, upper_last
, lower_last
;
557 upper_first
= extent
->first
;
558 lower_first
= extent
->lower_first
;
559 upper_last
= upper_first
+ extent
->count
- 1;
560 lower_last
= lower_first
+ extent
->count
- 1;
562 for (idx
= 0; idx
< new_map
->nr_extents
; idx
++) {
563 u32 prev_upper_first
, prev_lower_first
;
564 u32 prev_upper_last
, prev_lower_last
;
565 struct uid_gid_extent
*prev
;
567 prev
= &new_map
->extent
[idx
];
569 prev_upper_first
= prev
->first
;
570 prev_lower_first
= prev
->lower_first
;
571 prev_upper_last
= prev_upper_first
+ prev
->count
- 1;
572 prev_lower_last
= prev_lower_first
+ prev
->count
- 1;
574 /* Does the upper range intersect a previous extent? */
575 if ((prev_upper_first
<= upper_last
) &&
576 (prev_upper_last
>= upper_first
))
579 /* Does the lower range intersect a previous extent? */
580 if ((prev_lower_first
<= lower_last
) &&
581 (prev_lower_last
>= lower_first
))
588 static DEFINE_MUTEX(id_map_mutex
);
590 static ssize_t
map_write(struct file
*file
, const char __user
*buf
,
591 size_t count
, loff_t
*ppos
,
593 struct uid_gid_map
*map
,
594 struct uid_gid_map
*parent_map
)
596 struct seq_file
*seq
= file
->private_data
;
597 struct user_namespace
*ns
= seq
->private;
598 struct uid_gid_map new_map
;
600 struct uid_gid_extent
*extent
= NULL
;
601 unsigned long page
= 0;
602 char *kbuf
, *pos
, *next_line
;
603 ssize_t ret
= -EINVAL
;
606 * The id_map_mutex serializes all writes to any given map.
608 * Any map is only ever written once.
610 * An id map fits within 1 cache line on most architectures.
612 * On read nothing needs to be done unless you are on an
613 * architecture with a crazy cache coherency model like alpha.
615 * There is a one time data dependency between reading the
616 * count of the extents and the values of the extents. The
617 * desired behavior is to see the values of the extents that
618 * were written before the count of the extents.
620 * To achieve this smp_wmb() is used on guarantee the write
621 * order and smp_rmb() is guaranteed that we don't have crazy
622 * architectures returning stale data.
624 mutex_lock(&id_map_mutex
);
627 /* Only allow one successful write to the map */
628 if (map
->nr_extents
!= 0)
632 * Adjusting namespace settings requires capabilities on the target.
634 if (cap_valid(cap_setid
) && !file_ns_capable(file
, ns
, CAP_SYS_ADMIN
))
639 page
= __get_free_page(GFP_TEMPORARY
);
640 kbuf
= (char *) page
;
644 /* Only allow <= page size writes at the beginning of the file */
646 if ((*ppos
!= 0) || (count
>= PAGE_SIZE
))
649 /* Slurp in the user data */
651 if (copy_from_user(kbuf
, buf
, count
))
655 /* Parse the user data */
658 new_map
.nr_extents
= 0;
659 for (; pos
; pos
= next_line
) {
660 extent
= &new_map
.extent
[new_map
.nr_extents
];
662 /* Find the end of line and ensure I don't look past it */
663 next_line
= strchr(pos
, '\n');
667 if (*next_line
== '\0')
671 pos
= skip_spaces(pos
);
672 extent
->first
= simple_strtoul(pos
, &pos
, 10);
676 pos
= skip_spaces(pos
);
677 extent
->lower_first
= simple_strtoul(pos
, &pos
, 10);
681 pos
= skip_spaces(pos
);
682 extent
->count
= simple_strtoul(pos
, &pos
, 10);
683 if (*pos
&& !isspace(*pos
))
686 /* Verify there is not trailing junk on the line */
687 pos
= skip_spaces(pos
);
691 /* Verify we have been given valid starting values */
692 if ((extent
->first
== (u32
) -1) ||
693 (extent
->lower_first
== (u32
) -1))
696 /* Verify count is not zero and does not cause the
699 if ((extent
->first
+ extent
->count
) <= extent
->first
)
701 if ((extent
->lower_first
+ extent
->count
) <=
705 /* Do the ranges in extent overlap any previous extents? */
706 if (mappings_overlap(&new_map
, extent
))
709 new_map
.nr_extents
++;
711 /* Fail if the file contains too many extents */
712 if ((new_map
.nr_extents
== UID_GID_MAP_MAX_EXTENTS
) &&
716 /* Be very certaint the new map actually exists */
717 if (new_map
.nr_extents
== 0)
721 /* Validate the user is allowed to use user id's mapped to. */
722 if (!new_idmap_permitted(file
, ns
, cap_setid
, &new_map
))
725 /* Map the lower ids from the parent user namespace to the
726 * kernel global id space.
728 for (idx
= 0; idx
< new_map
.nr_extents
; idx
++) {
730 extent
= &new_map
.extent
[idx
];
732 lower_first
= map_id_range_down(parent_map
,
736 /* Fail if we can not map the specified extent to
737 * the kernel global id space.
739 if (lower_first
== (u32
) -1)
742 extent
->lower_first
= lower_first
;
745 /* Install the map */
746 memcpy(map
->extent
, new_map
.extent
,
747 new_map
.nr_extents
*sizeof(new_map
.extent
[0]));
749 map
->nr_extents
= new_map
.nr_extents
;
754 mutex_unlock(&id_map_mutex
);
760 ssize_t
proc_uid_map_write(struct file
*file
, const char __user
*buf
,
761 size_t size
, loff_t
*ppos
)
763 struct seq_file
*seq
= file
->private_data
;
764 struct user_namespace
*ns
= seq
->private;
765 struct user_namespace
*seq_ns
= seq_user_ns(seq
);
770 if ((seq_ns
!= ns
) && (seq_ns
!= ns
->parent
))
773 return map_write(file
, buf
, size
, ppos
, CAP_SETUID
,
774 &ns
->uid_map
, &ns
->parent
->uid_map
);
777 ssize_t
proc_gid_map_write(struct file
*file
, const char __user
*buf
,
778 size_t size
, loff_t
*ppos
)
780 struct seq_file
*seq
= file
->private_data
;
781 struct user_namespace
*ns
= seq
->private;
782 struct user_namespace
*seq_ns
= seq_user_ns(seq
);
787 if ((seq_ns
!= ns
) && (seq_ns
!= ns
->parent
))
790 return map_write(file
, buf
, size
, ppos
, CAP_SETGID
,
791 &ns
->gid_map
, &ns
->parent
->gid_map
);
794 ssize_t
proc_projid_map_write(struct file
*file
, const char __user
*buf
,
795 size_t size
, loff_t
*ppos
)
797 struct seq_file
*seq
= file
->private_data
;
798 struct user_namespace
*ns
= seq
->private;
799 struct user_namespace
*seq_ns
= seq_user_ns(seq
);
804 if ((seq_ns
!= ns
) && (seq_ns
!= ns
->parent
))
807 /* Anyone can set any valid project id no capability needed */
808 return map_write(file
, buf
, size
, ppos
, -1,
809 &ns
->projid_map
, &ns
->parent
->projid_map
);
812 static bool new_idmap_permitted(const struct file
*file
,
813 struct user_namespace
*ns
, int cap_setid
,
814 struct uid_gid_map
*new_map
)
816 /* Allow mapping to your own filesystem ids */
817 if ((new_map
->nr_extents
== 1) && (new_map
->extent
[0].count
== 1)) {
818 u32 id
= new_map
->extent
[0].lower_first
;
819 if (cap_setid
== CAP_SETUID
) {
820 kuid_t uid
= make_kuid(ns
->parent
, id
);
821 if (uid_eq(uid
, file
->f_cred
->fsuid
))
823 } else if (cap_setid
== CAP_SETGID
) {
824 kgid_t gid
= make_kgid(ns
->parent
, id
);
825 if (gid_eq(gid
, file
->f_cred
->fsgid
))
830 /* Allow anyone to set a mapping that doesn't require privilege */
831 if (!cap_valid(cap_setid
))
834 /* Allow the specified ids if we have the appropriate capability
835 * (CAP_SETUID or CAP_SETGID) over the parent user namespace.
836 * And the opener of the id file also had the approprpiate capability.
838 if (ns_capable(ns
->parent
, cap_setid
) &&
839 file_ns_capable(file
, ns
->parent
, cap_setid
))
845 static inline struct user_namespace
*to_user_ns(struct ns_common
*ns
)
847 return container_of(ns
, struct user_namespace
, ns
);
850 static struct ns_common
*userns_get(struct task_struct
*task
)
852 struct user_namespace
*user_ns
;
855 user_ns
= get_user_ns(__task_cred(task
)->user_ns
);
858 return user_ns
? &user_ns
->ns
: NULL
;
861 static void userns_put(struct ns_common
*ns
)
863 put_user_ns(to_user_ns(ns
));
866 static int userns_install(struct nsproxy
*nsproxy
, struct ns_common
*ns
)
868 struct user_namespace
*user_ns
= to_user_ns(ns
);
871 /* Don't allow gaining capabilities by reentering
872 * the same user namespace.
874 if (user_ns
== current_user_ns())
877 /* Threaded processes may not enter a different user namespace */
878 if (atomic_read(¤t
->mm
->mm_users
) > 1)
881 if (current
->fs
->users
!= 1)
884 if (!ns_capable(user_ns
, CAP_SYS_ADMIN
))
887 cred
= prepare_creds();
891 put_user_ns(cred
->user_ns
);
892 set_cred_user_ns(cred
, get_user_ns(user_ns
));
894 return commit_creds(cred
);
897 const struct proc_ns_operations userns_operations
= {
899 .type
= CLONE_NEWUSER
,
902 .install
= userns_install
,
905 static __init
int user_namespaces_init(void)
907 user_ns_cachep
= KMEM_CACHE(user_namespace
, SLAB_PANIC
);
910 subsys_initcall(user_namespaces_init
);