Version:  2.0.40 2.2.26 2.4.37 3.13 3.14 3.15 3.16 3.17 3.18 3.19 4.0 4.1 4.2 4.3 4.4 4.5 4.6 4.7 4.8 4.9 4.10

Linux/kernel/user_namespace.c

  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 
 26 static struct kmem_cache *user_ns_cachep __read_mostly;
 27 static DEFINE_MUTEX(userns_state_mutex);
 28 
 29 static bool new_idmap_permitted(const struct file *file,
 30                                 struct user_namespace *ns, int cap_setid,
 31                                 struct uid_gid_map *map);
 32 static void free_user_ns(struct work_struct *work);
 33 
 34 static struct ucounts *inc_user_namespaces(struct user_namespace *ns, kuid_t uid)
 35 {
 36         return inc_ucount(ns, uid, UCOUNT_USER_NAMESPACES);
 37 }
 38 
 39 static void dec_user_namespaces(struct ucounts *ucounts)
 40 {
 41         return dec_ucount(ucounts, UCOUNT_USER_NAMESPACES);
 42 }
 43 
 44 static 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  */
 71 int 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;
142 fail_keyring:
143 #ifdef CONFIG_PERSISTENT_KEYRINGS
144         key_put(ns->persistent_keyring_register);
145 #endif
146         ns_free_inum(&ns->ns);
147 fail_free:
148         kmem_cache_free(user_ns_cachep, ns);
149 fail_dec:
150         dec_user_namespaces(ucounts);
151 fail:
152         return ret;
153 }
154 
155 int 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 
175 static 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 
194 void __put_user_ns(struct user_namespace *ns)
195 {
196         schedule_work(&ns->work);
197 }
198 EXPORT_SYMBOL(__put_user_ns);
199 
200 static 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 
226 static 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 
249 static 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  */
285 kuid_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 }
290 EXPORT_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  */
304 uid_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 }
309 EXPORT_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  */
329 uid_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 }
338 EXPORT_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  */
353 kgid_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 }
358 EXPORT_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  */
372 gid_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 }
377 EXPORT_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  */
396 gid_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 }
405 EXPORT_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  */
420 kprojid_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 }
425 EXPORT_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  */
439 projid_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 }
444 EXPORT_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  */
464 projid_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 }
473 EXPORT_SYMBOL(from_kprojid_munged);
474 
475 
476 static 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 
497 static 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 
518 static 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 
539 static 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 
551 static 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 
558 static 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 
565 static 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 
572 static void *m_next(struct seq_file *seq, void *v, loff_t *pos)
573 {
574         (*pos)++;
575         return seq->op->start(seq, pos);
576 }
577 
578 static void m_stop(struct seq_file *seq, void *v)
579 {
580         return;
581 }
582 
583 const 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 
590 const 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 
597 const 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 
604 static 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 
640 static 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 = -EINVAL;
653 
654         /*
655          * The userns_state_mutex serializes all writes to any given map.
656          *
657          * Any map is only ever written once.
658          *
659          * An id map fits within 1 cache line on most architectures.
660          *
661          * On read nothing needs to be done unless you are on an
662          * architecture with a crazy cache coherency model like alpha.
663          *
664          * There is a one time data dependency between reading the
665          * count of the extents and the values of the extents.  The
666          * desired behavior is to see the values of the extents that
667          * were written before the count of the extents.
668          *
669          * To achieve this smp_wmb() is used on guarantee the write
670          * order and smp_rmb() is guaranteed that we don't have crazy
671          * architectures returning stale data.
672          */
673         mutex_lock(&userns_state_mutex);
674 
675         ret = -EPERM;
676         /* Only allow one successful write to the map */
677         if (map->nr_extents != 0)
678                 goto out;
679 
680         /*
681          * Adjusting namespace settings requires capabilities on the target.
682          */
683         if (cap_valid(cap_setid) && !file_ns_capable(file, ns, CAP_SYS_ADMIN))
684                 goto out;
685 
686         /* Only allow < page size writes at the beginning of the file */
687         ret = -EINVAL;
688         if ((*ppos != 0) || (count >= PAGE_SIZE))
689                 goto out;
690 
691         /* Slurp in the user data */
692         kbuf = memdup_user_nul(buf, count);
693         if (IS_ERR(kbuf)) {
694                 ret = PTR_ERR(kbuf);
695                 kbuf = NULL;
696                 goto out;
697         }
698 
699         /* Parse the user data */
700         ret = -EINVAL;
701         pos = kbuf;
702         new_map.nr_extents = 0;
703         for (; pos; pos = next_line) {
704                 extent = &new_map.extent[new_map.nr_extents];
705 
706                 /* Find the end of line and ensure I don't look past it */
707                 next_line = strchr(pos, '\n');
708                 if (next_line) {
709                         *next_line = '\0';
710                         next_line++;
711                         if (*next_line == '\0')
712                                 next_line = NULL;
713                 }
714 
715                 pos = skip_spaces(pos);
716                 extent->first = simple_strtoul(pos, &pos, 10);
717                 if (!isspace(*pos))
718                         goto out;
719 
720                 pos = skip_spaces(pos);
721                 extent->lower_first = simple_strtoul(pos, &pos, 10);
722                 if (!isspace(*pos))
723                         goto out;
724 
725                 pos = skip_spaces(pos);
726                 extent->count = simple_strtoul(pos, &pos, 10);
727                 if (*pos && !isspace(*pos))
728                         goto out;
729 
730                 /* Verify there is not trailing junk on the line */
731                 pos = skip_spaces(pos);
732                 if (*pos != '\0')
733                         goto out;
734 
735                 /* Verify we have been given valid starting values */
736                 if ((extent->first == (u32) -1) ||
737                     (extent->lower_first == (u32) -1))
738                         goto out;
739 
740                 /* Verify count is not zero and does not cause the
741                  * extent to wrap
742                  */
743                 if ((extent->first + extent->count) <= extent->first)
744                         goto out;
745                 if ((extent->lower_first + extent->count) <=
746                      extent->lower_first)
747                         goto out;
748 
749                 /* Do the ranges in extent overlap any previous extents? */
750                 if (mappings_overlap(&new_map, extent))
751                         goto out;
752 
753                 new_map.nr_extents++;
754 
755                 /* Fail if the file contains too many extents */
756                 if ((new_map.nr_extents == UID_GID_MAP_MAX_EXTENTS) &&
757                     (next_line != NULL))
758                         goto out;
759         }
760         /* Be very certaint the new map actually exists */
761         if (new_map.nr_extents == 0)
762                 goto out;
763 
764         ret = -EPERM;
765         /* Validate the user is allowed to use user id's mapped to. */
766         if (!new_idmap_permitted(file, ns, cap_setid, &new_map))
767                 goto out;
768 
769         /* Map the lower ids from the parent user namespace to the
770          * kernel global id space.
771          */
772         for (idx = 0; idx < new_map.nr_extents; idx++) {
773                 u32 lower_first;
774                 extent = &new_map.extent[idx];
775 
776                 lower_first = map_id_range_down(parent_map,
777                                                 extent->lower_first,
778                                                 extent->count);
779 
780                 /* Fail if we can not map the specified extent to
781                  * the kernel global id space.
782                  */
783                 if (lower_first == (u32) -1)
784                         goto out;
785 
786                 extent->lower_first = lower_first;
787         }
788 
789         /* Install the map */
790         memcpy(map->extent, new_map.extent,
791                 new_map.nr_extents*sizeof(new_map.extent[0]));
792         smp_wmb();
793         map->nr_extents = new_map.nr_extents;
794 
795         *ppos = count;
796         ret = count;
797 out:
798         mutex_unlock(&userns_state_mutex);
799         kfree(kbuf);
800         return ret;
801 }
802 
803 ssize_t proc_uid_map_write(struct file *file, const char __user *buf,
804                            size_t size, loff_t *ppos)
805 {
806         struct seq_file *seq = file->private_data;
807         struct user_namespace *ns = seq->private;
808         struct user_namespace *seq_ns = seq_user_ns(seq);
809 
810         if (!ns->parent)
811                 return -EPERM;
812 
813         if ((seq_ns != ns) && (seq_ns != ns->parent))
814                 return -EPERM;
815 
816         return map_write(file, buf, size, ppos, CAP_SETUID,
817                          &ns->uid_map, &ns->parent->uid_map);
818 }
819 
820 ssize_t proc_gid_map_write(struct file *file, const char __user *buf,
821                            size_t size, loff_t *ppos)
822 {
823         struct seq_file *seq = file->private_data;
824         struct user_namespace *ns = seq->private;
825         struct user_namespace *seq_ns = seq_user_ns(seq);
826 
827         if (!ns->parent)
828                 return -EPERM;
829 
830         if ((seq_ns != ns) && (seq_ns != ns->parent))
831                 return -EPERM;
832 
833         return map_write(file, buf, size, ppos, CAP_SETGID,
834                          &ns->gid_map, &ns->parent->gid_map);
835 }
836 
837 ssize_t proc_projid_map_write(struct file *file, const char __user *buf,
838                               size_t size, loff_t *ppos)
839 {
840         struct seq_file *seq = file->private_data;
841         struct user_namespace *ns = seq->private;
842         struct user_namespace *seq_ns = seq_user_ns(seq);
843 
844         if (!ns->parent)
845                 return -EPERM;
846 
847         if ((seq_ns != ns) && (seq_ns != ns->parent))
848                 return -EPERM;
849 
850         /* Anyone can set any valid project id no capability needed */
851         return map_write(file, buf, size, ppos, -1,
852                          &ns->projid_map, &ns->parent->projid_map);
853 }
854 
855 static bool new_idmap_permitted(const struct file *file,
856                                 struct user_namespace *ns, int cap_setid,
857                                 struct uid_gid_map *new_map)
858 {
859         const struct cred *cred = file->f_cred;
860         /* Don't allow mappings that would allow anything that wouldn't
861          * be allowed without the establishment of unprivileged mappings.
862          */
863         if ((new_map->nr_extents == 1) && (new_map->extent[0].count == 1) &&
864             uid_eq(ns->owner, cred->euid)) {
865                 u32 id = new_map->extent[0].lower_first;
866                 if (cap_setid == CAP_SETUID) {
867                         kuid_t uid = make_kuid(ns->parent, id);
868                         if (uid_eq(uid, cred->euid))
869                                 return true;
870                 } else if (cap_setid == CAP_SETGID) {
871                         kgid_t gid = make_kgid(ns->parent, id);
872                         if (!(ns->flags & USERNS_SETGROUPS_ALLOWED) &&
873                             gid_eq(gid, cred->egid))
874                                 return true;
875                 }
876         }
877 
878         /* Allow anyone to set a mapping that doesn't require privilege */
879         if (!cap_valid(cap_setid))
880                 return true;
881 
882         /* Allow the specified ids if we have the appropriate capability
883          * (CAP_SETUID or CAP_SETGID) over the parent user namespace.
884          * And the opener of the id file also had the approprpiate capability.
885          */
886         if (ns_capable(ns->parent, cap_setid) &&
887             file_ns_capable(file, ns->parent, cap_setid))
888                 return true;
889 
890         return false;
891 }
892 
893 int proc_setgroups_show(struct seq_file *seq, void *v)
894 {
895         struct user_namespace *ns = seq->private;
896         unsigned long userns_flags = ACCESS_ONCE(ns->flags);
897 
898         seq_printf(seq, "%s\n",
899                    (userns_flags & USERNS_SETGROUPS_ALLOWED) ?
900                    "allow" : "deny");
901         return 0;
902 }
903 
904 ssize_t proc_setgroups_write(struct file *file, const char __user *buf,
905                              size_t count, loff_t *ppos)
906 {
907         struct seq_file *seq = file->private_data;
908         struct user_namespace *ns = seq->private;
909         char kbuf[8], *pos;
910         bool setgroups_allowed;
911         ssize_t ret;
912 
913         /* Only allow a very narrow range of strings to be written */
914         ret = -EINVAL;
915         if ((*ppos != 0) || (count >= sizeof(kbuf)))
916                 goto out;
917 
918         /* What was written? */
919         ret = -EFAULT;
920         if (copy_from_user(kbuf, buf, count))
921                 goto out;
922         kbuf[count] = '\0';
923         pos = kbuf;
924 
925         /* What is being requested? */
926         ret = -EINVAL;
927         if (strncmp(pos, "allow", 5) == 0) {
928                 pos += 5;
929                 setgroups_allowed = true;
930         }
931         else if (strncmp(pos, "deny", 4) == 0) {
932                 pos += 4;
933                 setgroups_allowed = false;
934         }
935         else
936                 goto out;
937 
938         /* Verify there is not trailing junk on the line */
939         pos = skip_spaces(pos);
940         if (*pos != '\0')
941                 goto out;
942 
943         ret = -EPERM;
944         mutex_lock(&userns_state_mutex);
945         if (setgroups_allowed) {
946                 /* Enabling setgroups after setgroups has been disabled
947                  * is not allowed.
948                  */
949                 if (!(ns->flags & USERNS_SETGROUPS_ALLOWED))
950                         goto out_unlock;
951         } else {
952                 /* Permanently disabling setgroups after setgroups has
953                  * been enabled by writing the gid_map is not allowed.
954                  */
955                 if (ns->gid_map.nr_extents != 0)
956                         goto out_unlock;
957                 ns->flags &= ~USERNS_SETGROUPS_ALLOWED;
958         }
959         mutex_unlock(&userns_state_mutex);
960 
961         /* Report a successful write */
962         *ppos = count;
963         ret = count;
964 out:
965         return ret;
966 out_unlock:
967         mutex_unlock(&userns_state_mutex);
968         goto out;
969 }
970 
971 bool userns_may_setgroups(const struct user_namespace *ns)
972 {
973         bool allowed;
974 
975         mutex_lock(&userns_state_mutex);
976         /* It is not safe to use setgroups until a gid mapping in
977          * the user namespace has been established.
978          */
979         allowed = ns->gid_map.nr_extents != 0;
980         /* Is setgroups allowed? */
981         allowed = allowed && (ns->flags & USERNS_SETGROUPS_ALLOWED);
982         mutex_unlock(&userns_state_mutex);
983 
984         return allowed;
985 }
986 
987 /*
988  * Returns true if @ns is the same namespace as or a descendant of
989  * @target_ns.
990  */
991 bool current_in_userns(const struct user_namespace *target_ns)
992 {
993         struct user_namespace *ns;
994         for (ns = current_user_ns(); ns; ns = ns->parent) {
995                 if (ns == target_ns)
996                         return true;
997         }
998         return false;
999 }
1000 
1001 static inline struct user_namespace *to_user_ns(struct ns_common *ns)
1002 {
1003         return container_of(ns, struct user_namespace, ns);
1004 }
1005 
1006 static struct ns_common *userns_get(struct task_struct *task)
1007 {
1008         struct user_namespace *user_ns;
1009 
1010         rcu_read_lock();
1011         user_ns = get_user_ns(__task_cred(task)->user_ns);
1012         rcu_read_unlock();
1013 
1014         return user_ns ? &user_ns->ns : NULL;
1015 }
1016 
1017 static void userns_put(struct ns_common *ns)
1018 {
1019         put_user_ns(to_user_ns(ns));
1020 }
1021 
1022 static int userns_install(struct nsproxy *nsproxy, struct ns_common *ns)
1023 {
1024         struct user_namespace *user_ns = to_user_ns(ns);
1025         struct cred *cred;
1026 
1027         /* Don't allow gaining capabilities by reentering
1028          * the same user namespace.
1029          */
1030         if (user_ns == current_user_ns())
1031                 return -EINVAL;
1032 
1033         /* Tasks that share a thread group must share a user namespace */
1034         if (!thread_group_empty(current))
1035                 return -EINVAL;
1036 
1037         if (current->fs->users != 1)
1038                 return -EINVAL;
1039 
1040         if (!ns_capable(user_ns, CAP_SYS_ADMIN))
1041                 return -EPERM;
1042 
1043         cred = prepare_creds();
1044         if (!cred)
1045                 return -ENOMEM;
1046 
1047         put_user_ns(cred->user_ns);
1048         set_cred_user_ns(cred, get_user_ns(user_ns));
1049 
1050         return commit_creds(cred);
1051 }
1052 
1053 struct ns_common *ns_get_owner(struct ns_common *ns)
1054 {
1055         struct user_namespace *my_user_ns = current_user_ns();
1056         struct user_namespace *owner, *p;
1057 
1058         /* See if the owner is in the current user namespace */
1059         owner = p = ns->ops->owner(ns);
1060         for (;;) {
1061                 if (!p)
1062                         return ERR_PTR(-EPERM);
1063                 if (p == my_user_ns)
1064                         break;
1065                 p = p->parent;
1066         }
1067 
1068         return &get_user_ns(owner)->ns;
1069 }
1070 
1071 static struct user_namespace *userns_owner(struct ns_common *ns)
1072 {
1073         return to_user_ns(ns)->parent;
1074 }
1075 
1076 const struct proc_ns_operations userns_operations = {
1077         .name           = "user",
1078         .type           = CLONE_NEWUSER,
1079         .get            = userns_get,
1080         .put            = userns_put,
1081         .install        = userns_install,
1082         .owner          = userns_owner,
1083         .get_parent     = ns_get_owner,
1084 };
1085 
1086 static __init int user_namespaces_init(void)
1087 {
1088         user_ns_cachep = KMEM_CACHE(user_namespace, SLAB_PANIC);
1089         return 0;
1090 }
1091 subsys_initcall(user_namespaces_init);
1092 

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