projects/linux·blob v4.5 · refs

1006 lines · 25.4 KiB

1/*
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
5 * License.
6 */
7
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>
20#include <linux/fs.h>
21#include <linux/uaccess.h>
22#include <linux/ctype.h>
23#include <linux/projid.h>
24#include <linux/fs_struct.h>
25
26static struct kmem_cache *user_ns_cachep __read_mostly;
27static DEFINE_MUTEX(userns_state_mutex);
28
29static bool new_idmap_permitted(const struct file *file,
30 struct user_namespace *ns, int cap_setid,
31 struct uid_gid_map *map);
32
33static void set_cred_user_ns(struct cred *cred, struct user_namespace *user_ns)
34{
35 /* Start with the same capabilities as init but useless for doing
36 * anything as the capabilities are bound to the new user namespace.
37 */
38 cred->securebits = SECUREBITS_DEFAULT;
39 cred->cap_inheritable = CAP_EMPTY_SET;
40 cred->cap_permitted = CAP_FULL_SET;
41 cred->cap_effective = CAP_FULL_SET;
42 cred->cap_ambient = CAP_EMPTY_SET;
43 cred->cap_bset = CAP_FULL_SET;
44#ifdef CONFIG_KEYS
45 key_put(cred->request_key_auth);
46 cred->request_key_auth = NULL;
47#endif
48 /* tgcred will be cleared in our caller bc CLONE_THREAD won't be set */
49 cred->user_ns = user_ns;
50}
51
52/*
53 * Create a new user namespace, deriving the creator from the user in the
54 * passed credentials, and replacing that user with the new root user for the
55 * new namespace.
56 *
57 * This is called by copy_creds(), which will finish setting the target task's
58 * credentials.
59 */
60int create_user_ns(struct cred *new)
61{
62 struct user_namespace *ns, *parent_ns = new->user_ns;
63 kuid_t owner = new->euid;
64 kgid_t group = new->egid;
65 int ret;
66
67 if (parent_ns->level > 32)
68 return -EUSERS;
69
70 /*
71 * Verify that we can not violate the policy of which files
72 * may be accessed that is specified by the root directory,
73 * by verifing that the root directory is at the root of the
74 * mount namespace which allows all files to be accessed.
75 */
76 if (current_chrooted())
77 return -EPERM;
78
79 /* The creator needs a mapping in the parent user namespace
80 * or else we won't be able to reasonably tell userspace who
81 * created a user_namespace.
82 */
83 if (!kuid_has_mapping(parent_ns, owner) ||
84 !kgid_has_mapping(parent_ns, group))
85 return -EPERM;
86
87 ns = kmem_cache_zalloc(user_ns_cachep, GFP_KERNEL);
88 if (!ns)
89 return -ENOMEM;
90
91 ret = ns_alloc_inum(&ns->ns);
92 if (ret) {
93 kmem_cache_free(user_ns_cachep, ns);
94 return ret;
95 }
96 ns->ns.ops = &userns_operations;
97
98 atomic_set(&ns->count, 1);
99 /* Leave the new->user_ns reference with the new user namespace. */
100 ns->parent = parent_ns;
101 ns->level = parent_ns->level + 1;
102 ns->owner = owner;
103 ns->group = group;
104
105 /* Inherit USERNS_SETGROUPS_ALLOWED from our parent */
106 mutex_lock(&userns_state_mutex);
107 ns->flags = parent_ns->flags;
108 mutex_unlock(&userns_state_mutex);
109
110 set_cred_user_ns(new, ns);
111
112#ifdef CONFIG_PERSISTENT_KEYRINGS
113 init_rwsem(&ns->persistent_keyring_register_sem);
114#endif
115 return 0;
116}
117
118int unshare_userns(unsigned long unshare_flags, struct cred **new_cred)
119{
120 struct cred *cred;
121 int err = -ENOMEM;
122
123 if (!(unshare_flags & CLONE_NEWUSER))
124 return 0;
125
126 cred = prepare_creds();
127 if (cred) {
128 err = create_user_ns(cred);
129 if (err)
130 put_cred(cred);
131 else
132 *new_cred = cred;
133 }
134
135 return err;
136}
137
138void free_user_ns(struct user_namespace *ns)
139{
140 struct user_namespace *parent;
141
142 do {
143 parent = ns->parent;
144#ifdef CONFIG_PERSISTENT_KEYRINGS
145 key_put(ns->persistent_keyring_register);
146#endif
147 ns_free_inum(&ns->ns);
148 kmem_cache_free(user_ns_cachep, ns);
149 ns = parent;
150 } while (atomic_dec_and_test(&parent->count));
151}
152EXPORT_SYMBOL(free_user_ns);
153
154static u32 map_id_range_down(struct uid_gid_map *map, u32 id, u32 count)
155{
156 unsigned idx, extents;
157 u32 first, last, id2;
158
159 id2 = id + count - 1;
160
161 /* Find the matching extent */
162 extents = map->nr_extents;
163 smp_rmb();
164 for (idx = 0; idx < extents; idx++) {
165 first = map->extent[idx].first;
166 last = first + map->extent[idx].count - 1;
167 if (id >= first && id <= last &&
168 (id2 >= first && id2 <= last))
169 break;
170 }
171 /* Map the id or note failure */
172 if (idx < extents)
173 id = (id - first) + map->extent[idx].lower_first;
174 else
175 id = (u32) -1;
176
177 return id;
178}
179
180static u32 map_id_down(struct uid_gid_map *map, u32 id)
181{
182 unsigned idx, extents;
183 u32 first, last;
184
185 /* Find the matching extent */
186 extents = map->nr_extents;
187 smp_rmb();
188 for (idx = 0; idx < extents; idx++) {
189 first = map->extent[idx].first;
190 last = first + map->extent[idx].count - 1;
191 if (id >= first && id <= last)
192 break;
193 }
194 /* Map the id or note failure */
195 if (idx < extents)
196 id = (id - first) + map->extent[idx].lower_first;
197 else
198 id = (u32) -1;
199
200 return id;
201}
202
203static u32 map_id_up(struct uid_gid_map *map, u32 id)
204{
205 unsigned idx, extents;
206 u32 first, last;
207
208 /* Find the matching extent */
209 extents = map->nr_extents;
210 smp_rmb();
211 for (idx = 0; idx < extents; idx++) {
212 first = map->extent[idx].lower_first;
213 last = first + map->extent[idx].count - 1;
214 if (id >= first && id <= last)
215 break;
216 }
217 /* Map the id or note failure */
218 if (idx < extents)
219 id = (id - first) + map->extent[idx].first;
220 else
221 id = (u32) -1;
222
223 return id;
224}
225
226/**
227 * make_kuid - Map a user-namespace uid pair into a kuid.
228 * @ns: User namespace that the uid is in
229 * @uid: User identifier
230 *
231 * Maps a user-namespace uid pair into a kernel internal kuid,
232 * and returns that kuid.
233 *
234 * When there is no mapping defined for the user-namespace uid
235 * pair INVALID_UID is returned. Callers are expected to test
236 * for and handle INVALID_UID being returned. INVALID_UID
237 * may be tested for using uid_valid().
238 */
239kuid_t make_kuid(struct user_namespace *ns, uid_t uid)
240{
241 /* Map the uid to a global kernel uid */
242 return KUIDT_INIT(map_id_down(&ns->uid_map, uid));
243}
244EXPORT_SYMBOL(make_kuid);
245
246/**
247 * from_kuid - Create a uid from a kuid user-namespace pair.
248 * @targ: The user namespace we want a uid in.
249 * @kuid: The kernel internal uid to start with.
250 *
251 * Map @kuid into the user-namespace specified by @targ and
252 * return the resulting uid.
253 *
254 * There is always a mapping into the initial user_namespace.
255 *
256 * If @kuid has no mapping in @targ (uid_t)-1 is returned.
257 */
258uid_t from_kuid(struct user_namespace *targ, kuid_t kuid)
259{
260 /* Map the uid from a global kernel uid */
261 return map_id_up(&targ->uid_map, __kuid_val(kuid));
262}
263EXPORT_SYMBOL(from_kuid);
264
265/**
266 * from_kuid_munged - Create a uid from a kuid user-namespace pair.
267 * @targ: The user namespace we want a uid in.
268 * @kuid: The kernel internal uid to start with.
269 *
270 * Map @kuid into the user-namespace specified by @targ and
271 * return the resulting uid.
272 *
273 * There is always a mapping into the initial user_namespace.
274 *
275 * Unlike from_kuid from_kuid_munged never fails and always
276 * returns a valid uid. This makes from_kuid_munged appropriate
277 * for use in syscalls like stat and getuid where failing the
278 * system call and failing to provide a valid uid are not an
279 * options.
280 *
281 * If @kuid has no mapping in @targ overflowuid is returned.
282 */
283uid_t from_kuid_munged(struct user_namespace *targ, kuid_t kuid)
284{
285 uid_t uid;
286 uid = from_kuid(targ, kuid);
287
288 if (uid == (uid_t) -1)
289 uid = overflowuid;
290 return uid;
291}
292EXPORT_SYMBOL(from_kuid_munged);
293
294/**
295 * make_kgid - Map a user-namespace gid pair into a kgid.
296 * @ns: User namespace that the gid is in
297 * @gid: group identifier
298 *
299 * Maps a user-namespace gid pair into a kernel internal kgid,
300 * and returns that kgid.
301 *
302 * When there is no mapping defined for the user-namespace gid
303 * pair INVALID_GID is returned. Callers are expected to test
304 * for and handle INVALID_GID being returned. INVALID_GID may be
305 * tested for using gid_valid().
306 */
307kgid_t make_kgid(struct user_namespace *ns, gid_t gid)
308{
309 /* Map the gid to a global kernel gid */
310 return KGIDT_INIT(map_id_down(&ns->gid_map, gid));
311}
312EXPORT_SYMBOL(make_kgid);
313
314/**
315 * from_kgid - Create a gid from a kgid user-namespace pair.
316 * @targ: The user namespace we want a gid in.
317 * @kgid: The kernel internal gid to start with.
318 *
319 * Map @kgid into the user-namespace specified by @targ and
320 * return the resulting gid.
321 *
322 * There is always a mapping into the initial user_namespace.
323 *
324 * If @kgid has no mapping in @targ (gid_t)-1 is returned.
325 */
326gid_t from_kgid(struct user_namespace *targ, kgid_t kgid)
327{
328 /* Map the gid from a global kernel gid */
329 return map_id_up(&targ->gid_map, __kgid_val(kgid));
330}
331EXPORT_SYMBOL(from_kgid);
332
333/**
334 * from_kgid_munged - Create a gid from a kgid user-namespace pair.
335 * @targ: The user namespace we want a gid in.
336 * @kgid: The kernel internal gid to start with.
337 *
338 * Map @kgid into the user-namespace specified by @targ and
339 * return the resulting gid.
340 *
341 * There is always a mapping into the initial user_namespace.
342 *
343 * Unlike from_kgid from_kgid_munged never fails and always
344 * returns a valid gid. This makes from_kgid_munged appropriate
345 * for use in syscalls like stat and getgid where failing the
346 * system call and failing to provide a valid gid are not options.
347 *
348 * If @kgid has no mapping in @targ overflowgid is returned.
349 */
350gid_t from_kgid_munged(struct user_namespace *targ, kgid_t kgid)
351{
352 gid_t gid;
353 gid = from_kgid(targ, kgid);
354
355 if (gid == (gid_t) -1)
356 gid = overflowgid;
357 return gid;
358}
359EXPORT_SYMBOL(from_kgid_munged);
360
361/**
362 * make_kprojid - Map a user-namespace projid pair into a kprojid.
363 * @ns: User namespace that the projid is in
364 * @projid: Project identifier
365 *
366 * Maps a user-namespace uid pair into a kernel internal kuid,
367 * and returns that kuid.
368 *
369 * When there is no mapping defined for the user-namespace projid
370 * pair INVALID_PROJID is returned. Callers are expected to test
371 * for and handle handle INVALID_PROJID being returned. INVALID_PROJID
372 * may be tested for using projid_valid().
373 */
374kprojid_t make_kprojid(struct user_namespace *ns, projid_t projid)
375{
376 /* Map the uid to a global kernel uid */
377 return KPROJIDT_INIT(map_id_down(&ns->projid_map, projid));
378}
379EXPORT_SYMBOL(make_kprojid);
380
381/**
382 * from_kprojid - Create a projid from a kprojid user-namespace pair.
383 * @targ: The user namespace we want a projid in.
384 * @kprojid: The kernel internal project identifier to start with.
385 *
386 * Map @kprojid into the user-namespace specified by @targ and
387 * return the resulting projid.
388 *
389 * There is always a mapping into the initial user_namespace.
390 *
391 * If @kprojid has no mapping in @targ (projid_t)-1 is returned.
392 */
393projid_t from_kprojid(struct user_namespace *targ, kprojid_t kprojid)
394{
395 /* Map the uid from a global kernel uid */
396 return map_id_up(&targ->projid_map, __kprojid_val(kprojid));
397}
398EXPORT_SYMBOL(from_kprojid);
399
400/**
401 * from_kprojid_munged - Create a projiid from a kprojid user-namespace pair.
402 * @targ: The user namespace we want a projid in.
403 * @kprojid: The kernel internal projid to start with.
404 *
405 * Map @kprojid into the user-namespace specified by @targ and
406 * return the resulting projid.
407 *
408 * There is always a mapping into the initial user_namespace.
409 *
410 * Unlike from_kprojid from_kprojid_munged never fails and always
411 * returns a valid projid. This makes from_kprojid_munged
412 * appropriate for use in syscalls like stat and where
413 * failing the system call and failing to provide a valid projid are
414 * not an options.
415 *
416 * If @kprojid has no mapping in @targ OVERFLOW_PROJID is returned.
417 */
418projid_t from_kprojid_munged(struct user_namespace *targ, kprojid_t kprojid)
419{
420 projid_t projid;
421 projid = from_kprojid(targ, kprojid);
422
423 if (projid == (projid_t) -1)
424 projid = OVERFLOW_PROJID;
425 return projid;
426}
427EXPORT_SYMBOL(from_kprojid_munged);
428
429
430static int uid_m_show(struct seq_file *seq, void *v)
431{
432 struct user_namespace *ns = seq->private;
433 struct uid_gid_extent *extent = v;
434 struct user_namespace *lower_ns;
435 uid_t lower;
436
437 lower_ns = seq_user_ns(seq);
438 if ((lower_ns == ns) && lower_ns->parent)
439 lower_ns = lower_ns->parent;
440
441 lower = from_kuid(lower_ns, KUIDT_INIT(extent->lower_first));
442
443 seq_printf(seq, "%10u %10u %10u\n",
444 extent->first,
445 lower,
446 extent->count);
447
448 return 0;
449}
450
451static int gid_m_show(struct seq_file *seq, void *v)
452{
453 struct user_namespace *ns = seq->private;
454 struct uid_gid_extent *extent = v;
455 struct user_namespace *lower_ns;
456 gid_t lower;
457
458 lower_ns = seq_user_ns(seq);
459 if ((lower_ns == ns) && lower_ns->parent)
460 lower_ns = lower_ns->parent;
461
462 lower = from_kgid(lower_ns, KGIDT_INIT(extent->lower_first));
463
464 seq_printf(seq, "%10u %10u %10u\n",
465 extent->first,
466 lower,
467 extent->count);
468
469 return 0;
470}
471
472static int projid_m_show(struct seq_file *seq, void *v)
473{
474 struct user_namespace *ns = seq->private;
475 struct uid_gid_extent *extent = v;
476 struct user_namespace *lower_ns;
477 projid_t lower;
478
479 lower_ns = seq_user_ns(seq);
480 if ((lower_ns == ns) && lower_ns->parent)
481 lower_ns = lower_ns->parent;
482
483 lower = from_kprojid(lower_ns, KPROJIDT_INIT(extent->lower_first));
484
485 seq_printf(seq, "%10u %10u %10u\n",
486 extent->first,
487 lower,
488 extent->count);
489
490 return 0;
491}
492
493static void *m_start(struct seq_file *seq, loff_t *ppos,
494 struct uid_gid_map *map)
495{
496 struct uid_gid_extent *extent = NULL;
497 loff_t pos = *ppos;
498
499 if (pos < map->nr_extents)
500 extent = &map->extent[pos];
501
502 return extent;
503}
504
505static void *uid_m_start(struct seq_file *seq, loff_t *ppos)
506{
507 struct user_namespace *ns = seq->private;
508
509 return m_start(seq, ppos, &ns->uid_map);
510}
511
512static void *gid_m_start(struct seq_file *seq, loff_t *ppos)
513{
514 struct user_namespace *ns = seq->private;
515
516 return m_start(seq, ppos, &ns->gid_map);
517}
518
519static void *projid_m_start(struct seq_file *seq, loff_t *ppos)
520{
521 struct user_namespace *ns = seq->private;
522
523 return m_start(seq, ppos, &ns->projid_map);
524}
525
526static void *m_next(struct seq_file *seq, void *v, loff_t *pos)
527{
528 (*pos)++;
529 return seq->op->start(seq, pos);
530}
531
532static void m_stop(struct seq_file *seq, void *v)
533{
534 return;
535}
536
537const struct seq_operations proc_uid_seq_operations = {
538 .start = uid_m_start,
539 .stop = m_stop,
540 .next = m_next,
541 .show = uid_m_show,
542};
543
544const struct seq_operations proc_gid_seq_operations = {
545 .start = gid_m_start,
546 .stop = m_stop,
547 .next = m_next,
548 .show = gid_m_show,
549};
550
551const struct seq_operations proc_projid_seq_operations = {
552 .start = projid_m_start,
553 .stop = m_stop,
554 .next = m_next,
555 .show = projid_m_show,
556};
557
558static bool mappings_overlap(struct uid_gid_map *new_map,
559 struct uid_gid_extent *extent)
560{
561 u32 upper_first, lower_first, upper_last, lower_last;
562 unsigned idx;
563
564 upper_first = extent->first;
565 lower_first = extent->lower_first;
566 upper_last = upper_first + extent->count - 1;
567 lower_last = lower_first + extent->count - 1;
568
569 for (idx = 0; idx < new_map->nr_extents; idx++) {
570 u32 prev_upper_first, prev_lower_first;
571 u32 prev_upper_last, prev_lower_last;
572 struct uid_gid_extent *prev;
573
574 prev = &new_map->extent[idx];
575
576 prev_upper_first = prev->first;
577 prev_lower_first = prev->lower_first;
578 prev_upper_last = prev_upper_first + prev->count - 1;
579 prev_lower_last = prev_lower_first + prev->count - 1;
580
581 /* Does the upper range intersect a previous extent? */
582 if ((prev_upper_first <= upper_last) &&
583 (prev_upper_last >= upper_first))
584 return true;
585
586 /* Does the lower range intersect a previous extent? */
587 if ((prev_lower_first <= lower_last) &&
588 (prev_lower_last >= lower_first))
589 return true;
590 }
591 return false;
592}
593
594static ssize_t map_write(struct file *file, const char __user *buf,
595 size_t count, loff_t *ppos,
596 int cap_setid,
597 struct uid_gid_map *map,
598 struct uid_gid_map *parent_map)
599{
600 struct seq_file *seq = file->private_data;
601 struct user_namespace *ns = seq->private;
602 struct uid_gid_map new_map;
603 unsigned idx;
604 struct uid_gid_extent *extent = NULL;
605 char *kbuf = NULL, *pos, *next_line;
606 ssize_t ret = -EINVAL;
607
608 /*
609 * The userns_state_mutex serializes all writes to any given map.
610 *
611 * Any map is only ever written once.
612 *
613 * An id map fits within 1 cache line on most architectures.
614 *
615 * On read nothing needs to be done unless you are on an
616 * architecture with a crazy cache coherency model like alpha.
617 *
618 * There is a one time data dependency between reading the
619 * count of the extents and the values of the extents. The
620 * desired behavior is to see the values of the extents that
621 * were written before the count of the extents.
622 *
623 * To achieve this smp_wmb() is used on guarantee the write
624 * order and smp_rmb() is guaranteed that we don't have crazy
625 * architectures returning stale data.
626 */
627 mutex_lock(&userns_state_mutex);
628
629 ret = -EPERM;
630 /* Only allow one successful write to the map */
631 if (map->nr_extents != 0)
632 goto out;
633
634 /*
635 * Adjusting namespace settings requires capabilities on the target.
636 */
637 if (cap_valid(cap_setid) && !file_ns_capable(file, ns, CAP_SYS_ADMIN))
638 goto out;
639
640 /* Only allow < page size writes at the beginning of the file */
641 ret = -EINVAL;
642 if ((*ppos != 0) || (count >= PAGE_SIZE))
643 goto out;
644
645 /* Slurp in the user data */
646 kbuf = memdup_user_nul(buf, count);
647 if (IS_ERR(kbuf)) {
648 ret = PTR_ERR(kbuf);
649 kbuf = NULL;
650 goto out;
651 }
652
653 /* Parse the user data */
654 ret = -EINVAL;
655 pos = kbuf;
656 new_map.nr_extents = 0;
657 for (; pos; pos = next_line) {
658 extent = &new_map.extent[new_map.nr_extents];
659
660 /* Find the end of line and ensure I don't look past it */
661 next_line = strchr(pos, '\n');
662 if (next_line) {
663 *next_line = '\0';
664 next_line++;
665 if (*next_line == '\0')
666 next_line = NULL;
667 }
668
669 pos = skip_spaces(pos);
670 extent->first = simple_strtoul(pos, &pos, 10);
671 if (!isspace(*pos))
672 goto out;
673
674 pos = skip_spaces(pos);
675 extent->lower_first = simple_strtoul(pos, &pos, 10);
676 if (!isspace(*pos))
677 goto out;
678
679 pos = skip_spaces(pos);
680 extent->count = simple_strtoul(pos, &pos, 10);
681 if (*pos && !isspace(*pos))
682 goto out;
683
684 /* Verify there is not trailing junk on the line */
685 pos = skip_spaces(pos);
686 if (*pos != '\0')
687 goto out;
688
689 /* Verify we have been given valid starting values */
690 if ((extent->first == (u32) -1) ||
691 (extent->lower_first == (u32) -1))
692 goto out;
693
694 /* Verify count is not zero and does not cause the
695 * extent to wrap
696 */
697 if ((extent->first + extent->count) <= extent->first)
698 goto out;
699 if ((extent->lower_first + extent->count) <=
700 extent->lower_first)
701 goto out;
702
703 /* Do the ranges in extent overlap any previous extents? */
704 if (mappings_overlap(&new_map, extent))
705 goto out;
706
707 new_map.nr_extents++;
708
709 /* Fail if the file contains too many extents */
710 if ((new_map.nr_extents == UID_GID_MAP_MAX_EXTENTS) &&
711 (next_line != NULL))
712 goto out;
713 }
714 /* Be very certaint the new map actually exists */
715 if (new_map.nr_extents == 0)
716 goto out;
717
718 ret = -EPERM;
719 /* Validate the user is allowed to use user id's mapped to. */
720 if (!new_idmap_permitted(file, ns, cap_setid, &new_map))
721 goto out;
722
723 /* Map the lower ids from the parent user namespace to the
724 * kernel global id space.
725 */
726 for (idx = 0; idx < new_map.nr_extents; idx++) {
727 u32 lower_first;
728 extent = &new_map.extent[idx];
729
730 lower_first = map_id_range_down(parent_map,
731 extent->lower_first,
732 extent->count);
733
734 /* Fail if we can not map the specified extent to
735 * the kernel global id space.
736 */
737 if (lower_first == (u32) -1)
738 goto out;
739
740 extent->lower_first = lower_first;
741 }
742
743 /* Install the map */
744 memcpy(map->extent, new_map.extent,
745 new_map.nr_extents*sizeof(new_map.extent[0]));
746 smp_wmb();
747 map->nr_extents = new_map.nr_extents;
748
749 *ppos = count;
750 ret = count;
751out:
752 mutex_unlock(&userns_state_mutex);
753 kfree(kbuf);
754 return ret;
755}
756
757ssize_t proc_uid_map_write(struct file *file, const char __user *buf,
758 size_t size, loff_t *ppos)
759{
760 struct seq_file *seq = file->private_data;
761 struct user_namespace *ns = seq->private;
762 struct user_namespace *seq_ns = seq_user_ns(seq);
763
764 if (!ns->parent)
765 return -EPERM;
766
767 if ((seq_ns != ns) && (seq_ns != ns->parent))
768 return -EPERM;
769
770 return map_write(file, buf, size, ppos, CAP_SETUID,
771 &ns->uid_map, &ns->parent->uid_map);
772}
773
774ssize_t proc_gid_map_write(struct file *file, const char __user *buf,
775 size_t size, loff_t *ppos)
776{
777 struct seq_file *seq = file->private_data;
778 struct user_namespace *ns = seq->private;
779 struct user_namespace *seq_ns = seq_user_ns(seq);
780
781 if (!ns->parent)
782 return -EPERM;
783
784 if ((seq_ns != ns) && (seq_ns != ns->parent))
785 return -EPERM;
786
787 return map_write(file, buf, size, ppos, CAP_SETGID,
788 &ns->gid_map, &ns->parent->gid_map);
789}
790
791ssize_t proc_projid_map_write(struct file *file, const char __user *buf,
792 size_t size, loff_t *ppos)
793{
794 struct seq_file *seq = file->private_data;
795 struct user_namespace *ns = seq->private;
796 struct user_namespace *seq_ns = seq_user_ns(seq);
797
798 if (!ns->parent)
799 return -EPERM;
800
801 if ((seq_ns != ns) && (seq_ns != ns->parent))
802 return -EPERM;
803
804 /* Anyone can set any valid project id no capability needed */
805 return map_write(file, buf, size, ppos, -1,
806 &ns->projid_map, &ns->parent->projid_map);
807}
808
809static bool new_idmap_permitted(const struct file *file,
810 struct user_namespace *ns, int cap_setid,
811 struct uid_gid_map *new_map)
812{
813 const struct cred *cred = file->f_cred;
814 /* Don't allow mappings that would allow anything that wouldn't
815 * be allowed without the establishment of unprivileged mappings.
816 */
817 if ((new_map->nr_extents == 1) && (new_map->extent[0].count == 1) &&
818 uid_eq(ns->owner, cred->euid)) {
819 u32 id = new_map->extent[0].lower_first;
820 if (cap_setid == CAP_SETUID) {
821 kuid_t uid = make_kuid(ns->parent, id);
822 if (uid_eq(uid, cred->euid))
823 return true;
824 } else if (cap_setid == CAP_SETGID) {
825 kgid_t gid = make_kgid(ns->parent, id);
826 if (!(ns->flags & USERNS_SETGROUPS_ALLOWED) &&
827 gid_eq(gid, cred->egid))
828 return true;
829 }
830 }
831
832 /* Allow anyone to set a mapping that doesn't require privilege */
833 if (!cap_valid(cap_setid))
834 return true;
835
836 /* Allow the specified ids if we have the appropriate capability
837 * (CAP_SETUID or CAP_SETGID) over the parent user namespace.
838 * And the opener of the id file also had the approprpiate capability.
839 */
840 if (ns_capable(ns->parent, cap_setid) &&
841 file_ns_capable(file, ns->parent, cap_setid))
842 return true;
843
844 return false;
845}
846
847int proc_setgroups_show(struct seq_file *seq, void *v)
848{
849 struct user_namespace *ns = seq->private;
850 unsigned long userns_flags = ACCESS_ONCE(ns->flags);
851
852 seq_printf(seq, "%s\n",
853 (userns_flags & USERNS_SETGROUPS_ALLOWED) ?
854 "allow" : "deny");
855 return 0;
856}
857
858ssize_t proc_setgroups_write(struct file *file, const char __user *buf,
859 size_t count, loff_t *ppos)
860{
861 struct seq_file *seq = file->private_data;
862 struct user_namespace *ns = seq->private;
863 char kbuf[8], *pos;
864 bool setgroups_allowed;
865 ssize_t ret;
866
867 /* Only allow a very narrow range of strings to be written */
868 ret = -EINVAL;
869 if ((*ppos != 0) || (count >= sizeof(kbuf)))
870 goto out;
871
872 /* What was written? */
873 ret = -EFAULT;
874 if (copy_from_user(kbuf, buf, count))
875 goto out;
876 kbuf[count] = '\0';
877 pos = kbuf;
878
879 /* What is being requested? */
880 ret = -EINVAL;
881 if (strncmp(pos, "allow", 5) == 0) {
882 pos += 5;
883 setgroups_allowed = true;
884 }
885 else if (strncmp(pos, "deny", 4) == 0) {
886 pos += 4;
887 setgroups_allowed = false;
888 }
889 else
890 goto out;
891
892 /* Verify there is not trailing junk on the line */
893 pos = skip_spaces(pos);
894 if (*pos != '\0')
895 goto out;
896
897 ret = -EPERM;
898 mutex_lock(&userns_state_mutex);
899 if (setgroups_allowed) {
900 /* Enabling setgroups after setgroups has been disabled
901 * is not allowed.
902 */
903 if (!(ns->flags & USERNS_SETGROUPS_ALLOWED))
904 goto out_unlock;
905 } else {
906 /* Permanently disabling setgroups after setgroups has
907 * been enabled by writing the gid_map is not allowed.
908 */
909 if (ns->gid_map.nr_extents != 0)
910 goto out_unlock;
911 ns->flags &= ~USERNS_SETGROUPS_ALLOWED;
912 }
913 mutex_unlock(&userns_state_mutex);
914
915 /* Report a successful write */
916 *ppos = count;
917 ret = count;
918out:
919 return ret;
920out_unlock:
921 mutex_unlock(&userns_state_mutex);
922 goto out;
923}
924
925bool userns_may_setgroups(const struct user_namespace *ns)
926{
927 bool allowed;
928
929 mutex_lock(&userns_state_mutex);
930 /* It is not safe to use setgroups until a gid mapping in
931 * the user namespace has been established.
932 */
933 allowed = ns->gid_map.nr_extents != 0;
934 /* Is setgroups allowed? */
935 allowed = allowed && (ns->flags & USERNS_SETGROUPS_ALLOWED);
936 mutex_unlock(&userns_state_mutex);
937
938 return allowed;
939}
940
941static inline struct user_namespace *to_user_ns(struct ns_common *ns)
942{
943 return container_of(ns, struct user_namespace, ns);
944}
945
946static struct ns_common *userns_get(struct task_struct *task)
947{
948 struct user_namespace *user_ns;
949
950 rcu_read_lock();
951 user_ns = get_user_ns(__task_cred(task)->user_ns);
952 rcu_read_unlock();
953
954 return user_ns ? &user_ns->ns : NULL;
955}
956
957static void userns_put(struct ns_common *ns)
958{
959 put_user_ns(to_user_ns(ns));
960}
961
962static int userns_install(struct nsproxy *nsproxy, struct ns_common *ns)
963{
964 struct user_namespace *user_ns = to_user_ns(ns);
965 struct cred *cred;
966
967 /* Don't allow gaining capabilities by reentering
968 * the same user namespace.
969 */
970 if (user_ns == current_user_ns())
971 return -EINVAL;
972
973 /* Tasks that share a thread group must share a user namespace */
974 if (!thread_group_empty(current))
975 return -EINVAL;
976
977 if (current->fs->users != 1)
978 return -EINVAL;
979
980 if (!ns_capable(user_ns, CAP_SYS_ADMIN))
981 return -EPERM;
982
983 cred = prepare_creds();
984 if (!cred)
985 return -ENOMEM;
986
987 put_user_ns(cred->user_ns);
988 set_cred_user_ns(cred, get_user_ns(user_ns));
989
990 return commit_creds(cred);
991}
992
993const struct proc_ns_operations userns_operations = {
994 .name = "user",
995 .type = CLONE_NEWUSER,
996 .get = userns_get,
997 .put = userns_put,
998 .install = userns_install,
999};
1000
1001static __init int user_namespaces_init(void)
1002{
1003 user_ns_cachep = KMEM_CACHE(user_namespace, SLAB_PANIC);
1004 return 0;
1005}
1006subsys_initcall(user_namespaces_init);