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path: root/kernel/user_namespace.c (plain)
blob: f789bbba9b8eea645a2b4997f901c963c178af9c
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);
32static void free_user_ns(struct work_struct *work);
33
34static struct ucounts *inc_user_namespaces(struct user_namespace *ns, kuid_t uid)
35{
36 return inc_ucount(ns, uid, UCOUNT_USER_NAMESPACES);
37}
38
39static void dec_user_namespaces(struct ucounts *ucounts)
40{
41 return dec_ucount(ucounts, UCOUNT_USER_NAMESPACES);
42}
43
44static void set_cred_user_ns(struct cred *cred, struct user_namespace *user_ns)
45{
46 /* Start with the same capabilities as init but useless for doing
47 * anything as the capabilities are bound to the new user namespace.
48 */
49 cred->securebits = SECUREBITS_DEFAULT;
50 cred->cap_inheritable = CAP_EMPTY_SET;
51 cred->cap_permitted = CAP_FULL_SET;
52 cred->cap_effective = CAP_FULL_SET;
53 cred->cap_ambient = CAP_EMPTY_SET;
54 cred->cap_bset = CAP_FULL_SET;
55#ifdef CONFIG_KEYS
56 key_put(cred->request_key_auth);
57 cred->request_key_auth = NULL;
58#endif
59 /* tgcred will be cleared in our caller bc CLONE_THREAD won't be set */
60 cred->user_ns = user_ns;
61}
62
63/*
64 * Create a new user namespace, deriving the creator from the user in the
65 * passed credentials, and replacing that user with the new root user for the
66 * new namespace.
67 *
68 * This is called by copy_creds(), which will finish setting the target task's
69 * credentials.
70 */
71int create_user_ns(struct cred *new)
72{
73 struct user_namespace *ns, *parent_ns = new->user_ns;
74 kuid_t owner = new->euid;
75 kgid_t group = new->egid;
76 struct ucounts *ucounts;
77 int ret, i;
78
79 ret = -ENOSPC;
80 if (parent_ns->level > 32)
81 goto fail;
82
83 ucounts = inc_user_namespaces(parent_ns, owner);
84 if (!ucounts)
85 goto fail;
86
87 /*
88 * Verify that we can not violate the policy of which files
89 * may be accessed that is specified by the root directory,
90 * by verifing that the root directory is at the root of the
91 * mount namespace which allows all files to be accessed.
92 */
93 ret = -EPERM;
94 if (current_chrooted())
95 goto fail_dec;
96
97 /* The creator needs a mapping in the parent user namespace
98 * or else we won't be able to reasonably tell userspace who
99 * created a user_namespace.
100 */
101 ret = -EPERM;
102 if (!kuid_has_mapping(parent_ns, owner) ||
103 !kgid_has_mapping(parent_ns, group))
104 goto fail_dec;
105
106 ret = -ENOMEM;
107 ns = kmem_cache_zalloc(user_ns_cachep, GFP_KERNEL);
108 if (!ns)
109 goto fail_dec;
110
111 ret = ns_alloc_inum(&ns->ns);
112 if (ret)
113 goto fail_free;
114 ns->ns.ops = &userns_operations;
115
116 atomic_set(&ns->count, 1);
117 /* Leave the new->user_ns reference with the new user namespace. */
118 ns->parent = parent_ns;
119 ns->level = parent_ns->level + 1;
120 ns->owner = owner;
121 ns->group = group;
122 INIT_WORK(&ns->work, free_user_ns);
123 for (i = 0; i < UCOUNT_COUNTS; i++) {
124 ns->ucount_max[i] = INT_MAX;
125 }
126 ns->ucounts = ucounts;
127
128 /* Inherit USERNS_SETGROUPS_ALLOWED from our parent */
129 mutex_lock(&userns_state_mutex);
130 ns->flags = parent_ns->flags;
131 mutex_unlock(&userns_state_mutex);
132
133#ifdef CONFIG_PERSISTENT_KEYRINGS
134 init_rwsem(&ns->persistent_keyring_register_sem);
135#endif
136 ret = -ENOMEM;
137 if (!setup_userns_sysctls(ns))
138 goto fail_keyring;
139
140 set_cred_user_ns(new, ns);
141 return 0;
142fail_keyring:
143#ifdef CONFIG_PERSISTENT_KEYRINGS
144 key_put(ns->persistent_keyring_register);
145#endif
146 ns_free_inum(&ns->ns);
147fail_free:
148 kmem_cache_free(user_ns_cachep, ns);
149fail_dec:
150 dec_user_namespaces(ucounts);
151fail:
152 return ret;
153}
154
155int unshare_userns(unsigned long unshare_flags, struct cred **new_cred)
156{
157 struct cred *cred;
158 int err = -ENOMEM;
159
160 if (!(unshare_flags & CLONE_NEWUSER))
161 return 0;
162
163 cred = prepare_creds();
164 if (cred) {
165 err = create_user_ns(cred);
166 if (err)
167 put_cred(cred);
168 else
169 *new_cred = cred;
170 }
171
172 return err;
173}
174
175static void free_user_ns(struct work_struct *work)
176{
177 struct user_namespace *parent, *ns =
178 container_of(work, struct user_namespace, work);
179
180 do {
181 struct ucounts *ucounts = ns->ucounts;
182 parent = ns->parent;
183 retire_userns_sysctls(ns);
184#ifdef CONFIG_PERSISTENT_KEYRINGS
185 key_put(ns->persistent_keyring_register);
186#endif
187 ns_free_inum(&ns->ns);
188 kmem_cache_free(user_ns_cachep, ns);
189 dec_user_namespaces(ucounts);
190 ns = parent;
191 } while (atomic_dec_and_test(&parent->count));
192}
193
194void __put_user_ns(struct user_namespace *ns)
195{
196 schedule_work(&ns->work);
197}
198EXPORT_SYMBOL(__put_user_ns);
199
200static u32 map_id_range_down(struct uid_gid_map *map, u32 id, u32 count)
201{
202 unsigned idx, extents;
203 u32 first, last, id2;
204
205 id2 = id + count - 1;
206
207 /* Find the matching extent */
208 extents = map->nr_extents;
209 smp_rmb();
210 for (idx = 0; idx < extents; idx++) {
211 first = map->extent[idx].first;
212 last = first + map->extent[idx].count - 1;
213 if (id >= first && id <= last &&
214 (id2 >= first && id2 <= last))
215 break;
216 }
217 /* Map the id or note failure */
218 if (idx < extents)
219 id = (id - first) + map->extent[idx].lower_first;
220 else
221 id = (u32) -1;
222
223 return id;
224}
225
226static u32 map_id_down(struct uid_gid_map *map, u32 id)
227{
228 unsigned idx, extents;
229 u32 first, last;
230
231 /* Find the matching extent */
232 extents = map->nr_extents;
233 smp_rmb();
234 for (idx = 0; idx < extents; idx++) {
235 first = map->extent[idx].first;
236 last = first + map->extent[idx].count - 1;
237 if (id >= first && id <= last)
238 break;
239 }
240 /* Map the id or note failure */
241 if (idx < extents)
242 id = (id - first) + map->extent[idx].lower_first;
243 else
244 id = (u32) -1;
245
246 return id;
247}
248
249static u32 map_id_up(struct uid_gid_map *map, u32 id)
250{
251 unsigned idx, extents;
252 u32 first, last;
253
254 /* Find the matching extent */
255 extents = map->nr_extents;
256 smp_rmb();
257 for (idx = 0; idx < extents; idx++) {
258 first = map->extent[idx].lower_first;
259 last = first + map->extent[idx].count - 1;
260 if (id >= first && id <= last)
261 break;
262 }
263 /* Map the id or note failure */
264 if (idx < extents)
265 id = (id - first) + map->extent[idx].first;
266 else
267 id = (u32) -1;
268
269 return id;
270}
271
272/**
273 * make_kuid - Map a user-namespace uid pair into a kuid.
274 * @ns: User namespace that the uid is in
275 * @uid: User identifier
276 *
277 * Maps a user-namespace uid pair into a kernel internal kuid,
278 * and returns that kuid.
279 *
280 * When there is no mapping defined for the user-namespace uid
281 * pair INVALID_UID is returned. Callers are expected to test
282 * for and handle INVALID_UID being returned. INVALID_UID
283 * may be tested for using uid_valid().
284 */
285kuid_t make_kuid(struct user_namespace *ns, uid_t uid)
286{
287 /* Map the uid to a global kernel uid */
288 return KUIDT_INIT(map_id_down(&ns->uid_map, uid));
289}
290EXPORT_SYMBOL(make_kuid);
291
292/**
293 * from_kuid - Create a uid from a kuid user-namespace pair.
294 * @targ: The user namespace we want a uid in.
295 * @kuid: The kernel internal uid to start with.
296 *
297 * Map @kuid into the user-namespace specified by @targ and
298 * return the resulting uid.
299 *
300 * There is always a mapping into the initial user_namespace.
301 *
302 * If @kuid has no mapping in @targ (uid_t)-1 is returned.
303 */
304uid_t from_kuid(struct user_namespace *targ, kuid_t kuid)
305{
306 /* Map the uid from a global kernel uid */
307 return map_id_up(&targ->uid_map, __kuid_val(kuid));
308}
309EXPORT_SYMBOL(from_kuid);
310
311/**
312 * from_kuid_munged - Create a uid from a kuid user-namespace pair.
313 * @targ: The user namespace we want a uid in.
314 * @kuid: The kernel internal uid to start with.
315 *
316 * Map @kuid into the user-namespace specified by @targ and
317 * return the resulting uid.
318 *
319 * There is always a mapping into the initial user_namespace.
320 *
321 * Unlike from_kuid from_kuid_munged never fails and always
322 * returns a valid uid. This makes from_kuid_munged appropriate
323 * for use in syscalls like stat and getuid where failing the
324 * system call and failing to provide a valid uid are not an
325 * options.
326 *
327 * If @kuid has no mapping in @targ overflowuid is returned.
328 */
329uid_t from_kuid_munged(struct user_namespace *targ, kuid_t kuid)
330{
331 uid_t uid;
332 uid = from_kuid(targ, kuid);
333
334 if (uid == (uid_t) -1)
335 uid = overflowuid;
336 return uid;
337}
338EXPORT_SYMBOL(from_kuid_munged);
339
340/**
341 * make_kgid - Map a user-namespace gid pair into a kgid.
342 * @ns: User namespace that the gid is in
343 * @gid: group identifier
344 *
345 * Maps a user-namespace gid pair into a kernel internal kgid,
346 * and returns that kgid.
347 *
348 * When there is no mapping defined for the user-namespace gid
349 * pair INVALID_GID is returned. Callers are expected to test
350 * for and handle INVALID_GID being returned. INVALID_GID may be
351 * tested for using gid_valid().
352 */
353kgid_t make_kgid(struct user_namespace *ns, gid_t gid)
354{
355 /* Map the gid to a global kernel gid */
356 return KGIDT_INIT(map_id_down(&ns->gid_map, gid));
357}
358EXPORT_SYMBOL(make_kgid);
359
360/**
361 * from_kgid - Create a gid from a kgid user-namespace pair.
362 * @targ: The user namespace we want a gid in.
363 * @kgid: The kernel internal gid to start with.
364 *
365 * Map @kgid into the user-namespace specified by @targ and
366 * return the resulting gid.
367 *
368 * There is always a mapping into the initial user_namespace.
369 *
370 * If @kgid has no mapping in @targ (gid_t)-1 is returned.
371 */
372gid_t from_kgid(struct user_namespace *targ, kgid_t kgid)
373{
374 /* Map the gid from a global kernel gid */
375 return map_id_up(&targ->gid_map, __kgid_val(kgid));
376}
377EXPORT_SYMBOL(from_kgid);
378
379/**
380 * from_kgid_munged - Create a gid from a kgid user-namespace pair.
381 * @targ: The user namespace we want a gid in.
382 * @kgid: The kernel internal gid to start with.
383 *
384 * Map @kgid into the user-namespace specified by @targ and
385 * return the resulting gid.
386 *
387 * There is always a mapping into the initial user_namespace.
388 *
389 * Unlike from_kgid from_kgid_munged never fails and always
390 * returns a valid gid. This makes from_kgid_munged appropriate
391 * for use in syscalls like stat and getgid where failing the
392 * system call and failing to provide a valid gid are not options.
393 *
394 * If @kgid has no mapping in @targ overflowgid is returned.
395 */
396gid_t from_kgid_munged(struct user_namespace *targ, kgid_t kgid)
397{
398 gid_t gid;
399 gid = from_kgid(targ, kgid);
400
401 if (gid == (gid_t) -1)
402 gid = overflowgid;
403 return gid;
404}
405EXPORT_SYMBOL(from_kgid_munged);
406
407/**
408 * make_kprojid - Map a user-namespace projid pair into a kprojid.
409 * @ns: User namespace that the projid is in
410 * @projid: Project identifier
411 *
412 * Maps a user-namespace uid pair into a kernel internal kuid,
413 * and returns that kuid.
414 *
415 * When there is no mapping defined for the user-namespace projid
416 * pair INVALID_PROJID is returned. Callers are expected to test
417 * for and handle handle INVALID_PROJID being returned. INVALID_PROJID
418 * may be tested for using projid_valid().
419 */
420kprojid_t make_kprojid(struct user_namespace *ns, projid_t projid)
421{
422 /* Map the uid to a global kernel uid */
423 return KPROJIDT_INIT(map_id_down(&ns->projid_map, projid));
424}
425EXPORT_SYMBOL(make_kprojid);
426
427/**
428 * from_kprojid - Create a projid from a kprojid user-namespace pair.
429 * @targ: The user namespace we want a projid in.
430 * @kprojid: The kernel internal project identifier to start with.
431 *
432 * Map @kprojid into the user-namespace specified by @targ and
433 * return the resulting projid.
434 *
435 * There is always a mapping into the initial user_namespace.
436 *
437 * If @kprojid has no mapping in @targ (projid_t)-1 is returned.
438 */
439projid_t from_kprojid(struct user_namespace *targ, kprojid_t kprojid)
440{
441 /* Map the uid from a global kernel uid */
442 return map_id_up(&targ->projid_map, __kprojid_val(kprojid));
443}
444EXPORT_SYMBOL(from_kprojid);
445
446/**
447 * from_kprojid_munged - Create a projiid from a kprojid user-namespace pair.
448 * @targ: The user namespace we want a projid in.
449 * @kprojid: The kernel internal projid to start with.
450 *
451 * Map @kprojid into the user-namespace specified by @targ and
452 * return the resulting projid.
453 *
454 * There is always a mapping into the initial user_namespace.
455 *
456 * Unlike from_kprojid from_kprojid_munged never fails and always
457 * returns a valid projid. This makes from_kprojid_munged
458 * appropriate for use in syscalls like stat and where
459 * failing the system call and failing to provide a valid projid are
460 * not an options.
461 *
462 * If @kprojid has no mapping in @targ OVERFLOW_PROJID is returned.
463 */
464projid_t from_kprojid_munged(struct user_namespace *targ, kprojid_t kprojid)
465{
466 projid_t projid;
467 projid = from_kprojid(targ, kprojid);
468
469 if (projid == (projid_t) -1)
470 projid = OVERFLOW_PROJID;
471 return projid;
472}
473EXPORT_SYMBOL(from_kprojid_munged);
474
475
476static int uid_m_show(struct seq_file *seq, void *v)
477{
478 struct user_namespace *ns = seq->private;
479 struct uid_gid_extent *extent = v;
480 struct user_namespace *lower_ns;
481 uid_t lower;
482
483 lower_ns = seq_user_ns(seq);
484 if ((lower_ns == ns) && lower_ns->parent)
485 lower_ns = lower_ns->parent;
486
487 lower = from_kuid(lower_ns, KUIDT_INIT(extent->lower_first));
488
489 seq_printf(seq, "%10u %10u %10u\n",
490 extent->first,
491 lower,
492 extent->count);
493
494 return 0;
495}
496
497static int gid_m_show(struct seq_file *seq, void *v)
498{
499 struct user_namespace *ns = seq->private;
500 struct uid_gid_extent *extent = v;
501 struct user_namespace *lower_ns;
502 gid_t lower;
503
504 lower_ns = seq_user_ns(seq);
505 if ((lower_ns == ns) && lower_ns->parent)
506 lower_ns = lower_ns->parent;
507
508 lower = from_kgid(lower_ns, KGIDT_INIT(extent->lower_first));
509
510 seq_printf(seq, "%10u %10u %10u\n",
511 extent->first,
512 lower,
513 extent->count);
514
515 return 0;
516}
517
518static int projid_m_show(struct seq_file *seq, void *v)
519{
520 struct user_namespace *ns = seq->private;
521 struct uid_gid_extent *extent = v;
522 struct user_namespace *lower_ns;
523 projid_t lower;
524
525 lower_ns = seq_user_ns(seq);
526 if ((lower_ns == ns) && lower_ns->parent)
527 lower_ns = lower_ns->parent;
528
529 lower = from_kprojid(lower_ns, KPROJIDT_INIT(extent->lower_first));
530
531 seq_printf(seq, "%10u %10u %10u\n",
532 extent->first,
533 lower,
534 extent->count);
535
536 return 0;
537}
538
539static void *m_start(struct seq_file *seq, loff_t *ppos,
540 struct uid_gid_map *map)
541{
542 struct uid_gid_extent *extent = NULL;
543 loff_t pos = *ppos;
544
545 if (pos < map->nr_extents)
546 extent = &map->extent[pos];
547
548 return extent;
549}
550
551static void *uid_m_start(struct seq_file *seq, loff_t *ppos)
552{
553 struct user_namespace *ns = seq->private;
554
555 return m_start(seq, ppos, &ns->uid_map);
556}
557
558static void *gid_m_start(struct seq_file *seq, loff_t *ppos)
559{
560 struct user_namespace *ns = seq->private;
561
562 return m_start(seq, ppos, &ns->gid_map);
563}
564
565static void *projid_m_start(struct seq_file *seq, loff_t *ppos)
566{
567 struct user_namespace *ns = seq->private;
568
569 return m_start(seq, ppos, &ns->projid_map);
570}
571
572static void *m_next(struct seq_file *seq, void *v, loff_t *pos)
573{
574 (*pos)++;
575 return seq->op->start(seq, pos);
576}
577
578static void m_stop(struct seq_file *seq, void *v)
579{
580 return;
581}
582
583const struct seq_operations proc_uid_seq_operations = {
584 .start = uid_m_start,
585 .stop = m_stop,
586 .next = m_next,
587 .show = uid_m_show,
588};
589
590const struct seq_operations proc_gid_seq_operations = {
591 .start = gid_m_start,
592 .stop = m_stop,
593 .next = m_next,
594 .show = gid_m_show,
595};
596
597const struct seq_operations proc_projid_seq_operations = {
598 .start = projid_m_start,
599 .stop = m_stop,
600 .next = m_next,
601 .show = projid_m_show,
602};
603
604static bool mappings_overlap(struct uid_gid_map *new_map,
605 struct uid_gid_extent *extent)
606{
607 u32 upper_first, lower_first, upper_last, lower_last;
608 unsigned idx;
609
610 upper_first = extent->first;
611 lower_first = extent->lower_first;
612 upper_last = upper_first + extent->count - 1;
613 lower_last = lower_first + extent->count - 1;
614
615 for (idx = 0; idx < new_map->nr_extents; idx++) {
616 u32 prev_upper_first, prev_lower_first;
617 u32 prev_upper_last, prev_lower_last;
618 struct uid_gid_extent *prev;
619
620 prev = &new_map->extent[idx];
621
622 prev_upper_first = prev->first;
623 prev_lower_first = prev->lower_first;
624 prev_upper_last = prev_upper_first + prev->count - 1;
625 prev_lower_last = prev_lower_first + prev->count - 1;
626
627 /* Does the upper range intersect a previous extent? */
628 if ((prev_upper_first <= upper_last) &&
629 (prev_upper_last >= upper_first))
630 return true;
631
632 /* Does the lower range intersect a previous extent? */
633 if ((prev_lower_first <= lower_last) &&
634 (prev_lower_last >= lower_first))
635 return true;
636 }
637 return false;
638}
639
640static ssize_t map_write(struct file *file, const char __user *buf,
641 size_t count, loff_t *ppos,
642 int cap_setid,
643 struct uid_gid_map *map,
644 struct uid_gid_map *parent_map)
645{
646 struct seq_file *seq = file->private_data;
647 struct user_namespace *ns = seq->private;
648 struct uid_gid_map new_map;
649 unsigned idx;
650 struct uid_gid_extent *extent = NULL;
651 char *kbuf = NULL, *pos, *next_line;
652 ssize_t ret;
653
654 /* Only allow < page size writes at the beginning of the file */
655 if ((*ppos != 0) || (count >= PAGE_SIZE))
656 return -EINVAL;
657
658 /* Slurp in the user data */
659 kbuf = memdup_user_nul(buf, count);
660 if (IS_ERR(kbuf))
661 return PTR_ERR(kbuf);
662
663 /*
664 * The userns_state_mutex serializes all writes to any given map.
665 *
666 * Any map is only ever written once.
667 *
668 * An id map fits within 1 cache line on most architectures.
669 *
670 * On read nothing needs to be done unless you are on an
671 * architecture with a crazy cache coherency model like alpha.
672 *
673 * There is a one time data dependency between reading the
674 * count of the extents and the values of the extents. The
675 * desired behavior is to see the values of the extents that
676 * were written before the count of the extents.
677 *
678 * To achieve this smp_wmb() is used on guarantee the write
679 * order and smp_rmb() is guaranteed that we don't have crazy
680 * architectures returning stale data.
681 */
682 mutex_lock(&userns_state_mutex);
683
684 ret = -EPERM;
685 /* Only allow one successful write to the map */
686 if (map->nr_extents != 0)
687 goto out;
688
689 /*
690 * Adjusting namespace settings requires capabilities on the target.
691 */
692 if (cap_valid(cap_setid) && !file_ns_capable(file, ns, CAP_SYS_ADMIN))
693 goto out;
694
695 /* Parse the user data */
696 ret = -EINVAL;
697 pos = kbuf;
698 new_map.nr_extents = 0;
699 for (; pos; pos = next_line) {
700 extent = &new_map.extent[new_map.nr_extents];
701
702 /* Find the end of line and ensure I don't look past it */
703 next_line = strchr(pos, '\n');
704 if (next_line) {
705 *next_line = '\0';
706 next_line++;
707 if (*next_line == '\0')
708 next_line = NULL;
709 }
710
711 pos = skip_spaces(pos);
712 extent->first = simple_strtoul(pos, &pos, 10);
713 if (!isspace(*pos))
714 goto out;
715
716 pos = skip_spaces(pos);
717 extent->lower_first = simple_strtoul(pos, &pos, 10);
718 if (!isspace(*pos))
719 goto out;
720
721 pos = skip_spaces(pos);
722 extent->count = simple_strtoul(pos, &pos, 10);
723 if (*pos && !isspace(*pos))
724 goto out;
725
726 /* Verify there is not trailing junk on the line */
727 pos = skip_spaces(pos);
728 if (*pos != '\0')
729 goto out;
730
731 /* Verify we have been given valid starting values */
732 if ((extent->first == (u32) -1) ||
733 (extent->lower_first == (u32) -1))
734 goto out;
735
736 /* Verify count is not zero and does not cause the
737 * extent to wrap
738 */
739 if ((extent->first + extent->count) <= extent->first)
740 goto out;
741 if ((extent->lower_first + extent->count) <=
742 extent->lower_first)
743 goto out;
744
745 /* Do the ranges in extent overlap any previous extents? */
746 if (mappings_overlap(&new_map, extent))
747 goto out;
748
749 new_map.nr_extents++;
750
751 /* Fail if the file contains too many extents */
752 if ((new_map.nr_extents == UID_GID_MAP_MAX_EXTENTS) &&
753 (next_line != NULL))
754 goto out;
755 }
756 /* Be very certaint the new map actually exists */
757 if (new_map.nr_extents == 0)
758 goto out;
759
760 ret = -EPERM;
761 /* Validate the user is allowed to use user id's mapped to. */
762 if (!new_idmap_permitted(file, ns, cap_setid, &new_map))
763 goto out;
764
765 /* Map the lower ids from the parent user namespace to the
766 * kernel global id space.
767 */
768 for (idx = 0; idx < new_map.nr_extents; idx++) {
769 u32 lower_first;
770 extent = &new_map.extent[idx];
771
772 lower_first = map_id_range_down(parent_map,
773 extent->lower_first,
774 extent->count);
775
776 /* Fail if we can not map the specified extent to
777 * the kernel global id space.
778 */
779 if (lower_first == (u32) -1)
780 goto out;
781
782 extent->lower_first = lower_first;
783 }
784
785 /* Install the map */
786 memcpy(map->extent, new_map.extent,
787 new_map.nr_extents*sizeof(new_map.extent[0]));
788 smp_wmb();
789 map->nr_extents = new_map.nr_extents;
790
791 *ppos = count;
792 ret = count;
793out:
794 mutex_unlock(&userns_state_mutex);
795 kfree(kbuf);
796 return ret;
797}
798
799ssize_t proc_uid_map_write(struct file *file, const char __user *buf,
800 size_t size, loff_t *ppos)
801{
802 struct seq_file *seq = file->private_data;
803 struct user_namespace *ns = seq->private;
804 struct user_namespace *seq_ns = seq_user_ns(seq);
805
806 if (!ns->parent)
807 return -EPERM;
808
809 if ((seq_ns != ns) && (seq_ns != ns->parent))
810 return -EPERM;
811
812 return map_write(file, buf, size, ppos, CAP_SETUID,
813 &ns->uid_map, &ns->parent->uid_map);
814}
815
816ssize_t proc_gid_map_write(struct file *file, const char __user *buf,
817 size_t size, loff_t *ppos)
818{
819 struct seq_file *seq = file->private_data;
820 struct user_namespace *ns = seq->private;
821 struct user_namespace *seq_ns = seq_user_ns(seq);
822
823 if (!ns->parent)
824 return -EPERM;
825
826 if ((seq_ns != ns) && (seq_ns != ns->parent))
827 return -EPERM;
828
829 return map_write(file, buf, size, ppos, CAP_SETGID,
830 &ns->gid_map, &ns->parent->gid_map);
831}
832
833ssize_t proc_projid_map_write(struct file *file, const char __user *buf,
834 size_t size, loff_t *ppos)
835{
836 struct seq_file *seq = file->private_data;
837 struct user_namespace *ns = seq->private;
838 struct user_namespace *seq_ns = seq_user_ns(seq);
839
840 if (!ns->parent)
841 return -EPERM;
842
843 if ((seq_ns != ns) && (seq_ns != ns->parent))
844 return -EPERM;
845
846 /* Anyone can set any valid project id no capability needed */
847 return map_write(file, buf, size, ppos, -1,
848 &ns->projid_map, &ns->parent->projid_map);
849}
850
851static bool new_idmap_permitted(const struct file *file,
852 struct user_namespace *ns, int cap_setid,
853 struct uid_gid_map *new_map)
854{
855 const struct cred *cred = file->f_cred;
856 /* Don't allow mappings that would allow anything that wouldn't
857 * be allowed without the establishment of unprivileged mappings.
858 */
859 if ((new_map->nr_extents == 1) && (new_map->extent[0].count == 1) &&
860 uid_eq(ns->owner, cred->euid)) {
861 u32 id = new_map->extent[0].lower_first;
862 if (cap_setid == CAP_SETUID) {
863 kuid_t uid = make_kuid(ns->parent, id);
864 if (uid_eq(uid, cred->euid))
865 return true;
866 } else if (cap_setid == CAP_SETGID) {
867 kgid_t gid = make_kgid(ns->parent, id);
868 if (!(ns->flags & USERNS_SETGROUPS_ALLOWED) &&
869 gid_eq(gid, cred->egid))
870 return true;
871 }
872 }
873
874 /* Allow anyone to set a mapping that doesn't require privilege */
875 if (!cap_valid(cap_setid))
876 return true;
877
878 /* Allow the specified ids if we have the appropriate capability
879 * (CAP_SETUID or CAP_SETGID) over the parent user namespace.
880 * And the opener of the id file also had the approprpiate capability.
881 */
882 if (ns_capable(ns->parent, cap_setid) &&
883 file_ns_capable(file, ns->parent, cap_setid))
884 return true;
885
886 return false;
887}
888
889int proc_setgroups_show(struct seq_file *seq, void *v)
890{
891 struct user_namespace *ns = seq->private;
892 unsigned long userns_flags = ACCESS_ONCE(ns->flags);
893
894 seq_printf(seq, "%s\n",
895 (userns_flags & USERNS_SETGROUPS_ALLOWED) ?
896 "allow" : "deny");
897 return 0;
898}
899
900ssize_t proc_setgroups_write(struct file *file, const char __user *buf,
901 size_t count, loff_t *ppos)
902{
903 struct seq_file *seq = file->private_data;
904 struct user_namespace *ns = seq->private;
905 char kbuf[8], *pos;
906 bool setgroups_allowed;
907 ssize_t ret;
908
909 /* Only allow a very narrow range of strings to be written */
910 ret = -EINVAL;
911 if ((*ppos != 0) || (count >= sizeof(kbuf)))
912 goto out;
913
914 /* What was written? */
915 ret = -EFAULT;
916 if (copy_from_user(kbuf, buf, count))
917 goto out;
918 kbuf[count] = '\0';
919 pos = kbuf;
920
921 /* What is being requested? */
922 ret = -EINVAL;
923 if (strncmp(pos, "allow", 5) == 0) {
924 pos += 5;
925 setgroups_allowed = true;
926 }
927 else if (strncmp(pos, "deny", 4) == 0) {
928 pos += 4;
929 setgroups_allowed = false;
930 }
931 else
932 goto out;
933
934 /* Verify there is not trailing junk on the line */
935 pos = skip_spaces(pos);
936 if (*pos != '\0')
937 goto out;
938
939 ret = -EPERM;
940 mutex_lock(&userns_state_mutex);
941 if (setgroups_allowed) {
942 /* Enabling setgroups after setgroups has been disabled
943 * is not allowed.
944 */
945 if (!(ns->flags & USERNS_SETGROUPS_ALLOWED))
946 goto out_unlock;
947 } else {
948 /* Permanently disabling setgroups after setgroups has
949 * been enabled by writing the gid_map is not allowed.
950 */
951 if (ns->gid_map.nr_extents != 0)
952 goto out_unlock;
953 ns->flags &= ~USERNS_SETGROUPS_ALLOWED;
954 }
955 mutex_unlock(&userns_state_mutex);
956
957 /* Report a successful write */
958 *ppos = count;
959 ret = count;
960out:
961 return ret;
962out_unlock:
963 mutex_unlock(&userns_state_mutex);
964 goto out;
965}
966
967bool userns_may_setgroups(const struct user_namespace *ns)
968{
969 bool allowed;
970
971 mutex_lock(&userns_state_mutex);
972 /* It is not safe to use setgroups until a gid mapping in
973 * the user namespace has been established.
974 */
975 allowed = ns->gid_map.nr_extents != 0;
976 /* Is setgroups allowed? */
977 allowed = allowed && (ns->flags & USERNS_SETGROUPS_ALLOWED);
978 mutex_unlock(&userns_state_mutex);
979
980 return allowed;
981}
982
983/*
984 * Returns true if @ns is the same namespace as or a descendant of
985 * @target_ns.
986 */
987bool current_in_userns(const struct user_namespace *target_ns)
988{
989 struct user_namespace *ns;
990 for (ns = current_user_ns(); ns; ns = ns->parent) {
991 if (ns == target_ns)
992 return true;
993 }
994 return false;
995}
996
997static inline struct user_namespace *to_user_ns(struct ns_common *ns)
998{
999 return container_of(ns, struct user_namespace, ns);
1000}
1001
1002static struct ns_common *userns_get(struct task_struct *task)
1003{
1004 struct user_namespace *user_ns;
1005
1006 rcu_read_lock();
1007 user_ns = get_user_ns(__task_cred(task)->user_ns);
1008 rcu_read_unlock();
1009
1010 return user_ns ? &user_ns->ns : NULL;
1011}
1012
1013static void userns_put(struct ns_common *ns)
1014{
1015 put_user_ns(to_user_ns(ns));
1016}
1017
1018static int userns_install(struct nsproxy *nsproxy, struct ns_common *ns)
1019{
1020 struct user_namespace *user_ns = to_user_ns(ns);
1021 struct cred *cred;
1022
1023 /* Don't allow gaining capabilities by reentering
1024 * the same user namespace.
1025 */
1026 if (user_ns == current_user_ns())
1027 return -EINVAL;
1028
1029 /* Tasks that share a thread group must share a user namespace */
1030 if (!thread_group_empty(current))
1031 return -EINVAL;
1032
1033 if (current->fs->users != 1)
1034 return -EINVAL;
1035
1036 if (!ns_capable(user_ns, CAP_SYS_ADMIN))
1037 return -EPERM;
1038
1039 cred = prepare_creds();
1040 if (!cred)
1041 return -ENOMEM;
1042
1043 put_user_ns(cred->user_ns);
1044 set_cred_user_ns(cred, get_user_ns(user_ns));
1045
1046 return commit_creds(cred);
1047}
1048
1049struct ns_common *ns_get_owner(struct ns_common *ns)
1050{
1051 struct user_namespace *my_user_ns = current_user_ns();
1052 struct user_namespace *owner, *p;
1053
1054 /* See if the owner is in the current user namespace */
1055 owner = p = ns->ops->owner(ns);
1056 for (;;) {
1057 if (!p)
1058 return ERR_PTR(-EPERM);
1059 if (p == my_user_ns)
1060 break;
1061 p = p->parent;
1062 }
1063
1064 return &get_user_ns(owner)->ns;
1065}
1066
1067static struct user_namespace *userns_owner(struct ns_common *ns)
1068{
1069 return to_user_ns(ns)->parent;
1070}
1071
1072const struct proc_ns_operations userns_operations = {
1073 .name = "user",
1074 .type = CLONE_NEWUSER,
1075 .get = userns_get,
1076 .put = userns_put,
1077 .install = userns_install,
1078 .owner = userns_owner,
1079 .get_parent = ns_get_owner,
1080};
1081
1082static __init int user_namespaces_init(void)
1083{
1084 user_ns_cachep = KMEM_CACHE(user_namespace, SLAB_PANIC);
1085 return 0;
1086}
1087subsys_initcall(user_namespaces_init);
1088
generated by cgit at 2024-05-18 16:38:18 (GMT)