kernel/user_namespace.c

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This source file includes following definitions.
inc_user_namespaces
dec_user_namespaces
set_cred_user_ns
create_user_ns
unshare_userns
free_user_ns
__put_user_ns
cmp_map_id
map_id_range_down_max
map_id_range_down_base
map_id_range_down
map_id_down
map_id_up_base
map_id_up_max
map_id_up
make_kuid
from_kuid
from_kuid_munged
make_kgid
from_kgid
from_kgid_munged
make_kprojid
from_kprojid
from_kprojid_munged
uid_m_show
gid_m_show
projid_m_show
m_start
uid_m_start
gid_m_start
projid_m_start
m_next
m_stop
mappings_overlap
insert_extent
cmp_extents_forward
cmp_extents_reverse
sort_idmaps
map_write
proc_uid_map_write
proc_gid_map_write
proc_projid_map_write
new_idmap_permitted
proc_setgroups_show
proc_setgroups_write
userns_may_setgroups
in_userns
current_in_userns
to_user_ns
userns_get
userns_put
userns_install
ns_get_owner
userns_owner
user_namespaces_init
   1 // SPDX-License-Identifier: GPL-2.0-only
   2 
   3 #include <linux/export.h>
   4 #include <linux/nsproxy.h>
   5 #include <linux/slab.h>
   6 #include <linux/sched/signal.h>
   7 #include <linux/user_namespace.h>
   8 #include <linux/proc_ns.h>
   9 #include <linux/highuid.h>
  10 #include <linux/cred.h>
  11 #include <linux/securebits.h>
  12 #include <linux/keyctl.h>
  13 #include <linux/key-type.h>
  14 #include <keys/user-type.h>
  15 #include <linux/seq_file.h>
  16 #include <linux/fs.h>
  17 #include <linux/uaccess.h>
  18 #include <linux/ctype.h>
  19 #include <linux/projid.h>
  20 #include <linux/fs_struct.h>
  21 #include <linux/bsearch.h>
  22 #include <linux/sort.h>
  23 
  24 static struct kmem_cache *user_ns_cachep __read_mostly;
  25 static DEFINE_MUTEX(userns_state_mutex);
  26 
  27 static bool new_idmap_permitted(const struct file *file,
  28                                 struct user_namespace *ns, int cap_setid,
  29                                 struct uid_gid_map *map);
  30 static void free_user_ns(struct work_struct *work);
  31 
  32 static struct ucounts *inc_user_namespaces(struct user_namespace *ns, kuid_t uid)
  33 {
  34         return inc_ucount(ns, uid, UCOUNT_USER_NAMESPACES);
  35 }
  36 
  37 static void dec_user_namespaces(struct ucounts *ucounts)
  38 {
  39         return dec_ucount(ucounts, UCOUNT_USER_NAMESPACES);
  40 }
  41 
  42 static void set_cred_user_ns(struct cred *cred, struct user_namespace *user_ns)
  43 {
  44         /* Start with the same capabilities as init but useless for doing
  45          * anything as the capabilities are bound to the new user namespace.
  46          */
  47         cred->securebits = SECUREBITS_DEFAULT;
  48         cred->cap_inheritable = CAP_EMPTY_SET;
  49         cred->cap_permitted = CAP_FULL_SET;
  50         cred->cap_effective = CAP_FULL_SET;
  51         cred->cap_ambient = CAP_EMPTY_SET;
  52         cred->cap_bset = CAP_FULL_SET;
  53 #ifdef CONFIG_KEYS
  54         key_put(cred->request_key_auth);
  55         cred->request_key_auth = NULL;
  56 #endif
  57         /* tgcred will be cleared in our caller bc CLONE_THREAD won't be set */
  58         cred->user_ns = user_ns;
  59 }
  60 
  61 /*
  62  * Create a new user namespace, deriving the creator from the user in the
  63  * passed credentials, and replacing that user with the new root user for the
  64  * new namespace.
  65  *
  66  * This is called by copy_creds(), which will finish setting the target task's
  67  * credentials.
  68  */
  69 int create_user_ns(struct cred *new)
  70 {
  71         struct user_namespace *ns, *parent_ns = new->user_ns;
  72         kuid_t owner = new->euid;
  73         kgid_t group = new->egid;
  74         struct ucounts *ucounts;
  75         int ret, i;
  76 
  77         ret = -ENOSPC;
  78         if (parent_ns->level > 32)
  79                 goto fail;
  80 
  81         ucounts = inc_user_namespaces(parent_ns, owner);
  82         if (!ucounts)
  83                 goto fail;
  84 
  85         /*
  86          * Verify that we can not violate the policy of which files
  87          * may be accessed that is specified by the root directory,
  88          * by verifing that the root directory is at the root of the
  89          * mount namespace which allows all files to be accessed.
  90          */
  91         ret = -EPERM;
  92         if (current_chrooted())
  93                 goto fail_dec;
  94 
  95         /* The creator needs a mapping in the parent user namespace
  96          * or else we won't be able to reasonably tell userspace who
  97          * created a user_namespace.
  98          */
  99         ret = -EPERM;
 100         if (!kuid_has_mapping(parent_ns, owner) ||
 101             !kgid_has_mapping(parent_ns, group))
 102                 goto fail_dec;
 103 
 104         ret = -ENOMEM;
 105         ns = kmem_cache_zalloc(user_ns_cachep, GFP_KERNEL);
 106         if (!ns)
 107                 goto fail_dec;
 108 
 109         ret = ns_alloc_inum(&ns->ns);
 110         if (ret)
 111                 goto fail_free;
 112         ns->ns.ops = &userns_operations;
 113 
 114         atomic_set(&ns->count, 1);
 115         /* Leave the new->user_ns reference with the new user namespace. */
 116         ns->parent = parent_ns;
 117         ns->level = parent_ns->level + 1;
 118         ns->owner = owner;
 119         ns->group = group;
 120         INIT_WORK(&ns->work, free_user_ns);
 121         for (i = 0; i < UCOUNT_COUNTS; i++) {
 122                 ns->ucount_max[i] = INT_MAX;
 123         }
 124         ns->ucounts = ucounts;
 125 
 126         /* Inherit USERNS_SETGROUPS_ALLOWED from our parent */
 127         mutex_lock(&userns_state_mutex);
 128         ns->flags = parent_ns->flags;
 129         mutex_unlock(&userns_state_mutex);
 130 
 131 #ifdef CONFIG_KEYS
 132         INIT_LIST_HEAD(&ns->keyring_name_list);
 133         init_rwsem(&ns->keyring_sem);
 134 #endif
 135         ret = -ENOMEM;
 136         if (!setup_userns_sysctls(ns))
 137                 goto fail_keyring;
 138 
 139         set_cred_user_ns(new, ns);
 140         return 0;
 141 fail_keyring:
 142 #ifdef CONFIG_PERSISTENT_KEYRINGS
 143         key_put(ns->persistent_keyring_register);
 144 #endif
 145         ns_free_inum(&ns->ns);
 146 fail_free:
 147         kmem_cache_free(user_ns_cachep, ns);
 148 fail_dec:
 149         dec_user_namespaces(ucounts);
 150 fail:
 151         return ret;
 152 }
 153 
 154 int unshare_userns(unsigned long unshare_flags, struct cred **new_cred)
 155 {
 156         struct cred *cred;
 157         int err = -ENOMEM;
 158 
 159         if (!(unshare_flags & CLONE_NEWUSER))
 160                 return 0;
 161 
 162         cred = prepare_creds();
 163         if (cred) {
 164                 err = create_user_ns(cred);
 165                 if (err)
 166                         put_cred(cred);
 167                 else
 168                         *new_cred = cred;
 169         }
 170 
 171         return err;
 172 }
 173 
 174 static void free_user_ns(struct work_struct *work)
 175 {
 176         struct user_namespace *parent, *ns =
 177                 container_of(work, struct user_namespace, work);
 178 
 179         do {
 180                 struct ucounts *ucounts = ns->ucounts;
 181                 parent = ns->parent;
 182                 if (ns->gid_map.nr_extents > UID_GID_MAP_MAX_BASE_EXTENTS) {
 183                         kfree(ns->gid_map.forward);
 184                         kfree(ns->gid_map.reverse);
 185                 }
 186                 if (ns->uid_map.nr_extents > UID_GID_MAP_MAX_BASE_EXTENTS) {
 187                         kfree(ns->uid_map.forward);
 188                         kfree(ns->uid_map.reverse);
 189                 }
 190                 if (ns->projid_map.nr_extents > UID_GID_MAP_MAX_BASE_EXTENTS) {
 191                         kfree(ns->projid_map.forward);
 192                         kfree(ns->projid_map.reverse);
 193                 }
 194                 retire_userns_sysctls(ns);
 195                 key_free_user_ns(ns);
 196                 ns_free_inum(&ns->ns);
 197                 kmem_cache_free(user_ns_cachep, ns);
 198                 dec_user_namespaces(ucounts);
 199                 ns = parent;
 200         } while (atomic_dec_and_test(&parent->count));
 201 }
 202 
 203 void __put_user_ns(struct user_namespace *ns)
 204 {
 205         schedule_work(&ns->work);
 206 }
 207 EXPORT_SYMBOL(__put_user_ns);
 208 
 209 /**
 210  * idmap_key struct holds the information necessary to find an idmapping in a
 211  * sorted idmap array. It is passed to cmp_map_id() as first argument.
 212  */
 213 struct idmap_key {
 214         bool map_up; /* true  -> id from kid; false -> kid from id */
 215         u32 id; /* id to find */
 216         u32 count; /* == 0 unless used with map_id_range_down() */
 217 };
 218 
 219 /**
 220  * cmp_map_id - Function to be passed to bsearch() to find the requested
 221  * idmapping. Expects struct idmap_key to be passed via @k.
 222  */
 223 static int cmp_map_id(const void *k, const void *e)
 224 {
 225         u32 first, last, id2;
 226         const struct idmap_key *key = k;
 227         const struct uid_gid_extent *el = e;
 228 
 229         id2 = key->id + key->count - 1;
 230 
 231         /* handle map_id_{down,up}() */
 232         if (key->map_up)
 233                 first = el->lower_first;
 234         else
 235                 first = el->first;
 236 
 237         last = first + el->count - 1;
 238 
 239         if (key->id >= first && key->id <= last &&
 240             (id2 >= first && id2 <= last))
 241                 return 0;
 242 
 243         if (key->id < first || id2 < first)
 244                 return -1;
 245 
 246         return 1;
 247 }
 248 
 249 /**
 250  * map_id_range_down_max - Find idmap via binary search in ordered idmap array.
 251  * Can only be called if number of mappings exceeds UID_GID_MAP_MAX_BASE_EXTENTS.
 252  */
 253 static struct uid_gid_extent *
 254 map_id_range_down_max(unsigned extents, struct uid_gid_map *map, u32 id, u32 count)
 255 {
 256         struct idmap_key key;
 257 
 258         key.map_up = false;
 259         key.count = count;
 260         key.id = id;
 261 
 262         return bsearch(&key, map->forward, extents,
 263                        sizeof(struct uid_gid_extent), cmp_map_id);
 264 }
 265 
 266 /**
 267  * map_id_range_down_base - Find idmap via binary search in static extent array.
 268  * Can only be called if number of mappings is equal or less than
 269  * UID_GID_MAP_MAX_BASE_EXTENTS.
 270  */
 271 static struct uid_gid_extent *
 272 map_id_range_down_base(unsigned extents, struct uid_gid_map *map, u32 id, u32 count)
 273 {
 274         unsigned idx;
 275         u32 first, last, id2;
 276 
 277         id2 = id + count - 1;
 278 
 279         /* Find the matching extent */
 280         for (idx = 0; idx < extents; idx++) {
 281                 first = map->extent[idx].first;
 282                 last = first + map->extent[idx].count - 1;
 283                 if (id >= first && id <= last &&
 284                     (id2 >= first && id2 <= last))
 285                         return &map->extent[idx];
 286         }
 287         return NULL;
 288 }
 289 
 290 static u32 map_id_range_down(struct uid_gid_map *map, u32 id, u32 count)
 291 {
 292         struct uid_gid_extent *extent;
 293         unsigned extents = map->nr_extents;
 294         smp_rmb();
 295 
 296         if (extents <= UID_GID_MAP_MAX_BASE_EXTENTS)
 297                 extent = map_id_range_down_base(extents, map, id, count);
 298         else
 299                 extent = map_id_range_down_max(extents, map, id, count);
 300 
 301         /* Map the id or note failure */
 302         if (extent)
 303                 id = (id - extent->first) + extent->lower_first;
 304         else
 305                 id = (u32) -1;
 306 
 307         return id;
 308 }
 309 
 310 static u32 map_id_down(struct uid_gid_map *map, u32 id)
 311 {
 312         return map_id_range_down(map, id, 1);
 313 }
 314 
 315 /**
 316  * map_id_up_base - Find idmap via binary search in static extent array.
 317  * Can only be called if number of mappings is equal or less than
 318  * UID_GID_MAP_MAX_BASE_EXTENTS.
 319  */
 320 static struct uid_gid_extent *
 321 map_id_up_base(unsigned extents, struct uid_gid_map *map, u32 id)
 322 {
 323         unsigned idx;
 324         u32 first, last;
 325 
 326         /* Find the matching extent */
 327         for (idx = 0; idx < extents; idx++) {
 328                 first = map->extent[idx].lower_first;
 329                 last = first + map->extent[idx].count - 1;
 330                 if (id >= first && id <= last)
 331                         return &map->extent[idx];
 332         }
 333         return NULL;
 334 }
 335 
 336 /**
 337  * map_id_up_max - Find idmap via binary search in ordered idmap array.
 338  * Can only be called if number of mappings exceeds UID_GID_MAP_MAX_BASE_EXTENTS.
 339  */
 340 static struct uid_gid_extent *
 341 map_id_up_max(unsigned extents, struct uid_gid_map *map, u32 id)
 342 {
 343         struct idmap_key key;
 344 
 345         key.map_up = true;
 346         key.count = 1;
 347         key.id = id;
 348 
 349         return bsearch(&key, map->reverse, extents,
 350                        sizeof(struct uid_gid_extent), cmp_map_id);
 351 }
 352 
 353 static u32 map_id_up(struct uid_gid_map *map, u32 id)
 354 {
 355         struct uid_gid_extent *extent;
 356         unsigned extents = map->nr_extents;
 357         smp_rmb();
 358 
 359         if (extents <= UID_GID_MAP_MAX_BASE_EXTENTS)
 360                 extent = map_id_up_base(extents, map, id);
 361         else
 362                 extent = map_id_up_max(extents, map, id);
 363 
 364         /* Map the id or note failure */
 365         if (extent)
 366                 id = (id - extent->lower_first) + extent->first;
 367         else
 368                 id = (u32) -1;
 369 
 370         return id;
 371 }
 372 
 373 /**
 374  *      make_kuid - Map a user-namespace uid pair into a kuid.
 375  *      @ns:  User namespace that the uid is in
 376  *      @uid: User identifier
 377  *
 378  *      Maps a user-namespace uid pair into a kernel internal kuid,
 379  *      and returns that kuid.
 380  *
 381  *      When there is no mapping defined for the user-namespace uid
 382  *      pair INVALID_UID is returned.  Callers are expected to test
 383  *      for and handle INVALID_UID being returned.  INVALID_UID
 384  *      may be tested for using uid_valid().
 385  */
 386 kuid_t make_kuid(struct user_namespace *ns, uid_t uid)
 387 {
 388         /* Map the uid to a global kernel uid */
 389         return KUIDT_INIT(map_id_down(&ns->uid_map, uid));
 390 }
 391 EXPORT_SYMBOL(make_kuid);
 392 
 393 /**
 394  *      from_kuid - Create a uid from a kuid user-namespace pair.
 395  *      @targ: The user namespace we want a uid in.
 396  *      @kuid: The kernel internal uid to start with.
 397  *
 398  *      Map @kuid into the user-namespace specified by @targ and
 399  *      return the resulting uid.
 400  *
 401  *      There is always a mapping into the initial user_namespace.
 402  *
 403  *      If @kuid has no mapping in @targ (uid_t)-1 is returned.
 404  */
 405 uid_t from_kuid(struct user_namespace *targ, kuid_t kuid)
 406 {
 407         /* Map the uid from a global kernel uid */
 408         return map_id_up(&targ->uid_map, __kuid_val(kuid));
 409 }
 410 EXPORT_SYMBOL(from_kuid);
 411 
 412 /**
 413  *      from_kuid_munged - Create a uid from a kuid user-namespace pair.
 414  *      @targ: The user namespace we want a uid in.
 415  *      @kuid: The kernel internal uid to start with.
 416  *
 417  *      Map @kuid into the user-namespace specified by @targ and
 418  *      return the resulting uid.
 419  *
 420  *      There is always a mapping into the initial user_namespace.
 421  *
 422  *      Unlike from_kuid from_kuid_munged never fails and always
 423  *      returns a valid uid.  This makes from_kuid_munged appropriate
 424  *      for use in syscalls like stat and getuid where failing the
 425  *      system call and failing to provide a valid uid are not an
 426  *      options.
 427  *
 428  *      If @kuid has no mapping in @targ overflowuid is returned.
 429  */
 430 uid_t from_kuid_munged(struct user_namespace *targ, kuid_t kuid)
 431 {
 432         uid_t uid;
 433         uid = from_kuid(targ, kuid);
 434 
 435         if (uid == (uid_t) -1)
 436                 uid = overflowuid;
 437         return uid;
 438 }
 439 EXPORT_SYMBOL(from_kuid_munged);
 440 
 441 /**
 442  *      make_kgid - Map a user-namespace gid pair into a kgid.
 443  *      @ns:  User namespace that the gid is in
 444  *      @gid: group identifier
 445  *
 446  *      Maps a user-namespace gid pair into a kernel internal kgid,
 447  *      and returns that kgid.
 448  *
 449  *      When there is no mapping defined for the user-namespace gid
 450  *      pair INVALID_GID is returned.  Callers are expected to test
 451  *      for and handle INVALID_GID being returned.  INVALID_GID may be
 452  *      tested for using gid_valid().
 453  */
 454 kgid_t make_kgid(struct user_namespace *ns, gid_t gid)
 455 {
 456         /* Map the gid to a global kernel gid */
 457         return KGIDT_INIT(map_id_down(&ns->gid_map, gid));
 458 }
 459 EXPORT_SYMBOL(make_kgid);
 460 
 461 /**
 462  *      from_kgid - Create a gid from a kgid user-namespace pair.
 463  *      @targ: The user namespace we want a gid in.
 464  *      @kgid: The kernel internal gid to start with.
 465  *
 466  *      Map @kgid into the user-namespace specified by @targ and
 467  *      return the resulting gid.
 468  *
 469  *      There is always a mapping into the initial user_namespace.
 470  *
 471  *      If @kgid has no mapping in @targ (gid_t)-1 is returned.
 472  */
 473 gid_t from_kgid(struct user_namespace *targ, kgid_t kgid)
 474 {
 475         /* Map the gid from a global kernel gid */
 476         return map_id_up(&targ->gid_map, __kgid_val(kgid));
 477 }
 478 EXPORT_SYMBOL(from_kgid);
 479 
 480 /**
 481  *      from_kgid_munged - Create a gid from a kgid user-namespace pair.
 482  *      @targ: The user namespace we want a gid in.
 483  *      @kgid: The kernel internal gid to start with.
 484  *
 485  *      Map @kgid into the user-namespace specified by @targ and
 486  *      return the resulting gid.
 487  *
 488  *      There is always a mapping into the initial user_namespace.
 489  *
 490  *      Unlike from_kgid from_kgid_munged never fails and always
 491  *      returns a valid gid.  This makes from_kgid_munged appropriate
 492  *      for use in syscalls like stat and getgid where failing the
 493  *      system call and failing to provide a valid gid are not options.
 494  *
 495  *      If @kgid has no mapping in @targ overflowgid is returned.
 496  */
 497 gid_t from_kgid_munged(struct user_namespace *targ, kgid_t kgid)
 498 {
 499         gid_t gid;
 500         gid = from_kgid(targ, kgid);
 501 
 502         if (gid == (gid_t) -1)
 503                 gid = overflowgid;
 504         return gid;
 505 }
 506 EXPORT_SYMBOL(from_kgid_munged);
 507 
 508 /**
 509  *      make_kprojid - Map a user-namespace projid pair into a kprojid.
 510  *      @ns:  User namespace that the projid is in
 511  *      @projid: Project identifier
 512  *
 513  *      Maps a user-namespace uid pair into a kernel internal kuid,
 514  *      and returns that kuid.
 515  *
 516  *      When there is no mapping defined for the user-namespace projid
 517  *      pair INVALID_PROJID is returned.  Callers are expected to test
 518  *      for and handle handle INVALID_PROJID being returned.  INVALID_PROJID
 519  *      may be tested for using projid_valid().
 520  */
 521 kprojid_t make_kprojid(struct user_namespace *ns, projid_t projid)
 522 {
 523         /* Map the uid to a global kernel uid */
 524         return KPROJIDT_INIT(map_id_down(&ns->projid_map, projid));
 525 }
 526 EXPORT_SYMBOL(make_kprojid);
 527 
 528 /**
 529  *      from_kprojid - Create a projid from a kprojid user-namespace pair.
 530  *      @targ: The user namespace we want a projid in.
 531  *      @kprojid: The kernel internal project identifier to start with.
 532  *
 533  *      Map @kprojid into the user-namespace specified by @targ and
 534  *      return the resulting projid.
 535  *
 536  *      There is always a mapping into the initial user_namespace.
 537  *
 538  *      If @kprojid has no mapping in @targ (projid_t)-1 is returned.
 539  */
 540 projid_t from_kprojid(struct user_namespace *targ, kprojid_t kprojid)
 541 {
 542         /* Map the uid from a global kernel uid */
 543         return map_id_up(&targ->projid_map, __kprojid_val(kprojid));
 544 }
 545 EXPORT_SYMBOL(from_kprojid);
 546 
 547 /**
 548  *      from_kprojid_munged - Create a projiid from a kprojid user-namespace pair.
 549  *      @targ: The user namespace we want a projid in.
 550  *      @kprojid: The kernel internal projid to start with.
 551  *
 552  *      Map @kprojid into the user-namespace specified by @targ and
 553  *      return the resulting projid.
 554  *
 555  *      There is always a mapping into the initial user_namespace.
 556  *
 557  *      Unlike from_kprojid from_kprojid_munged never fails and always
 558  *      returns a valid projid.  This makes from_kprojid_munged
 559  *      appropriate for use in syscalls like stat and where
 560  *      failing the system call and failing to provide a valid projid are
 561  *      not an options.
 562  *
 563  *      If @kprojid has no mapping in @targ OVERFLOW_PROJID is returned.
 564  */
 565 projid_t from_kprojid_munged(struct user_namespace *targ, kprojid_t kprojid)
 566 {
 567         projid_t projid;
 568         projid = from_kprojid(targ, kprojid);
 569 
 570         if (projid == (projid_t) -1)
 571                 projid = OVERFLOW_PROJID;
 572         return projid;
 573 }
 574 EXPORT_SYMBOL(from_kprojid_munged);
 575 
 576 
 577 static int uid_m_show(struct seq_file *seq, void *v)
 578 {
 579         struct user_namespace *ns = seq->private;
 580         struct uid_gid_extent *extent = v;
 581         struct user_namespace *lower_ns;
 582         uid_t lower;
 583 
 584         lower_ns = seq_user_ns(seq);
 585         if ((lower_ns == ns) && lower_ns->parent)
 586                 lower_ns = lower_ns->parent;
 587 
 588         lower = from_kuid(lower_ns, KUIDT_INIT(extent->lower_first));
 589 
 590         seq_printf(seq, "%10u %10u %10u\n",
 591                 extent->first,
 592                 lower,
 593                 extent->count);
 594 
 595         return 0;
 596 }
 597 
 598 static int gid_m_show(struct seq_file *seq, void *v)
 599 {
 600         struct user_namespace *ns = seq->private;
 601         struct uid_gid_extent *extent = v;
 602         struct user_namespace *lower_ns;
 603         gid_t lower;
 604 
 605         lower_ns = seq_user_ns(seq);
 606         if ((lower_ns == ns) && lower_ns->parent)
 607                 lower_ns = lower_ns->parent;
 608 
 609         lower = from_kgid(lower_ns, KGIDT_INIT(extent->lower_first));
 610 
 611         seq_printf(seq, "%10u %10u %10u\n",
 612                 extent->first,
 613                 lower,
 614                 extent->count);
 615 
 616         return 0;
 617 }
 618 
 619 static int projid_m_show(struct seq_file *seq, void *v)
 620 {
 621         struct user_namespace *ns = seq->private;
 622         struct uid_gid_extent *extent = v;
 623         struct user_namespace *lower_ns;
 624         projid_t lower;
 625 
 626         lower_ns = seq_user_ns(seq);
 627         if ((lower_ns == ns) && lower_ns->parent)
 628                 lower_ns = lower_ns->parent;
 629 
 630         lower = from_kprojid(lower_ns, KPROJIDT_INIT(extent->lower_first));
 631 
 632         seq_printf(seq, "%10u %10u %10u\n",
 633                 extent->first,
 634                 lower,
 635                 extent->count);
 636 
 637         return 0;
 638 }
 639 
 640 static void *m_start(struct seq_file *seq, loff_t *ppos,
 641                      struct uid_gid_map *map)
 642 {
 643         loff_t pos = *ppos;
 644         unsigned extents = map->nr_extents;
 645         smp_rmb();
 646 
 647         if (pos >= extents)
 648                 return NULL;
 649 
 650         if (extents <= UID_GID_MAP_MAX_BASE_EXTENTS)
 651                 return &map->extent[pos];
 652 
 653         return &map->forward[pos];
 654 }
 655 
 656 static void *uid_m_start(struct seq_file *seq, loff_t *ppos)
 657 {
 658         struct user_namespace *ns = seq->private;
 659 
 660         return m_start(seq, ppos, &ns->uid_map);
 661 }
 662 
 663 static void *gid_m_start(struct seq_file *seq, loff_t *ppos)
 664 {
 665         struct user_namespace *ns = seq->private;
 666 
 667         return m_start(seq, ppos, &ns->gid_map);
 668 }
 669 
 670 static void *projid_m_start(struct seq_file *seq, loff_t *ppos)
 671 {
 672         struct user_namespace *ns = seq->private;
 673 
 674         return m_start(seq, ppos, &ns->projid_map);
 675 }
 676 
 677 static void *m_next(struct seq_file *seq, void *v, loff_t *pos)
 678 {
 679         (*pos)++;
 680         return seq->op->start(seq, pos);
 681 }
 682 
 683 static void m_stop(struct seq_file *seq, void *v)
 684 {
 685         return;
 686 }
 687 
 688 const struct seq_operations proc_uid_seq_operations = {
 689         .start = uid_m_start,
 690         .stop = m_stop,
 691         .next = m_next,
 692         .show = uid_m_show,
 693 };
 694 
 695 const struct seq_operations proc_gid_seq_operations = {
 696         .start = gid_m_start,
 697         .stop = m_stop,
 698         .next = m_next,
 699         .show = gid_m_show,
 700 };
 701 
 702 const struct seq_operations proc_projid_seq_operations = {
 703         .start = projid_m_start,
 704         .stop = m_stop,
 705         .next = m_next,
 706         .show = projid_m_show,
 707 };
 708 
 709 static bool mappings_overlap(struct uid_gid_map *new_map,
 710                              struct uid_gid_extent *extent)
 711 {
 712         u32 upper_first, lower_first, upper_last, lower_last;
 713         unsigned idx;
 714 
 715         upper_first = extent->first;
 716         lower_first = extent->lower_first;
 717         upper_last = upper_first + extent->count - 1;
 718         lower_last = lower_first + extent->count - 1;
 719 
 720         for (idx = 0; idx < new_map->nr_extents; idx++) {
 721                 u32 prev_upper_first, prev_lower_first;
 722                 u32 prev_upper_last, prev_lower_last;
 723                 struct uid_gid_extent *prev;
 724 
 725                 if (new_map->nr_extents <= UID_GID_MAP_MAX_BASE_EXTENTS)
 726                         prev = &new_map->extent[idx];
 727                 else
 728                         prev = &new_map->forward[idx];
 729 
 730                 prev_upper_first = prev->first;
 731                 prev_lower_first = prev->lower_first;
 732                 prev_upper_last = prev_upper_first + prev->count - 1;
 733                 prev_lower_last = prev_lower_first + prev->count - 1;
 734 
 735                 /* Does the upper range intersect a previous extent? */
 736                 if ((prev_upper_first <= upper_last) &&
 737                     (prev_upper_last >= upper_first))
 738                         return true;
 739 
 740                 /* Does the lower range intersect a previous extent? */
 741                 if ((prev_lower_first <= lower_last) &&
 742                     (prev_lower_last >= lower_first))
 743                         return true;
 744         }
 745         return false;
 746 }
 747 
 748 /**
 749  * insert_extent - Safely insert a new idmap extent into struct uid_gid_map.
 750  * Takes care to allocate a 4K block of memory if the number of mappings exceeds
 751  * UID_GID_MAP_MAX_BASE_EXTENTS.
 752  */
 753 static int insert_extent(struct uid_gid_map *map, struct uid_gid_extent *extent)
 754 {
 755         struct uid_gid_extent *dest;
 756 
 757         if (map->nr_extents == UID_GID_MAP_MAX_BASE_EXTENTS) {
 758                 struct uid_gid_extent *forward;
 759 
 760                 /* Allocate memory for 340 mappings. */
 761                 forward = kmalloc_array(UID_GID_MAP_MAX_EXTENTS,
 762                                         sizeof(struct uid_gid_extent),
 763                                         GFP_KERNEL);
 764                 if (!forward)
 765                         return -ENOMEM;
 766 
 767                 /* Copy over memory. Only set up memory for the forward pointer.
 768                  * Defer the memory setup for the reverse pointer.
 769                  */
 770                 memcpy(forward, map->extent,
 771                        map->nr_extents * sizeof(map->extent[0]));
 772 
 773                 map->forward = forward;
 774                 map->reverse = NULL;
 775         }
 776 
 777         if (map->nr_extents < UID_GID_MAP_MAX_BASE_EXTENTS)
 778                 dest = &map->extent[map->nr_extents];
 779         else
 780                 dest = &map->forward[map->nr_extents];
 781 
 782         *dest = *extent;
 783         map->nr_extents++;
 784         return 0;
 785 }
 786 
 787 /* cmp function to sort() forward mappings */
 788 static int cmp_extents_forward(const void *a, const void *b)
 789 {
 790         const struct uid_gid_extent *e1 = a;
 791         const struct uid_gid_extent *e2 = b;
 792 
 793         if (e1->first < e2->first)
 794                 return -1;
 795 
 796         if (e1->first > e2->first)
 797                 return 1;
 798 
 799         return 0;
 800 }
 801 
 802 /* cmp function to sort() reverse mappings */
 803 static int cmp_extents_reverse(const void *a, const void *b)
 804 {
 805         const struct uid_gid_extent *e1 = a;
 806         const struct uid_gid_extent *e2 = b;
 807 
 808         if (e1->lower_first < e2->lower_first)
 809                 return -1;
 810 
 811         if (e1->lower_first > e2->lower_first)
 812                 return 1;
 813 
 814         return 0;
 815 }
 816 
 817 /**
 818  * sort_idmaps - Sorts an array of idmap entries.
 819  * Can only be called if number of mappings exceeds UID_GID_MAP_MAX_BASE_EXTENTS.
 820  */
 821 static int sort_idmaps(struct uid_gid_map *map)
 822 {
 823         if (map->nr_extents <= UID_GID_MAP_MAX_BASE_EXTENTS)
 824                 return 0;
 825 
 826         /* Sort forward array. */
 827         sort(map->forward, map->nr_extents, sizeof(struct uid_gid_extent),
 828              cmp_extents_forward, NULL);
 829 
 830         /* Only copy the memory from forward we actually need. */
 831         map->reverse = kmemdup(map->forward,
 832                                map->nr_extents * sizeof(struct uid_gid_extent),
 833                                GFP_KERNEL);
 834         if (!map->reverse)
 835                 return -ENOMEM;
 836 
 837         /* Sort reverse array. */
 838         sort(map->reverse, map->nr_extents, sizeof(struct uid_gid_extent),
 839              cmp_extents_reverse, NULL);
 840 
 841         return 0;
 842 }
 843 
 844 static ssize_t map_write(struct file *file, const char __user *buf,
 845                          size_t count, loff_t *ppos,
 846                          int cap_setid,
 847                          struct uid_gid_map *map,
 848                          struct uid_gid_map *parent_map)
 849 {
 850         struct seq_file *seq = file->private_data;
 851         struct user_namespace *ns = seq->private;
 852         struct uid_gid_map new_map;
 853         unsigned idx;
 854         struct uid_gid_extent extent;
 855         char *kbuf = NULL, *pos, *next_line;
 856         ssize_t ret;
 857 
 858         /* Only allow < page size writes at the beginning of the file */
 859         if ((*ppos != 0) || (count >= PAGE_SIZE))
 860                 return -EINVAL;
 861 
 862         /* Slurp in the user data */
 863         kbuf = memdup_user_nul(buf, count);
 864         if (IS_ERR(kbuf))
 865                 return PTR_ERR(kbuf);
 866 
 867         /*
 868          * The userns_state_mutex serializes all writes to any given map.
 869          *
 870          * Any map is only ever written once.
 871          *
 872          * An id map fits within 1 cache line on most architectures.
 873          *
 874          * On read nothing needs to be done unless you are on an
 875          * architecture with a crazy cache coherency model like alpha.
 876          *
 877          * There is a one time data dependency between reading the
 878          * count of the extents and the values of the extents.  The
 879          * desired behavior is to see the values of the extents that
 880          * were written before the count of the extents.
 881          *
 882          * To achieve this smp_wmb() is used on guarantee the write
 883          * order and smp_rmb() is guaranteed that we don't have crazy
 884          * architectures returning stale data.
 885          */
 886         mutex_lock(&userns_state_mutex);
 887 
 888         memset(&new_map, 0, sizeof(struct uid_gid_map));
 889 
 890         ret = -EPERM;
 891         /* Only allow one successful write to the map */
 892         if (map->nr_extents != 0)
 893                 goto out;
 894 
 895         /*
 896          * Adjusting namespace settings requires capabilities on the target.
 897          */
 898         if (cap_valid(cap_setid) && !file_ns_capable(file, ns, CAP_SYS_ADMIN))
 899                 goto out;
 900 
 901         /* Parse the user data */
 902         ret = -EINVAL;
 903         pos = kbuf;
 904         for (; pos; pos = next_line) {
 905 
 906                 /* Find the end of line and ensure I don't look past it */
 907                 next_line = strchr(pos, '\n');
 908                 if (next_line) {
 909                         *next_line = '\0';
 910                         next_line++;
 911                         if (*next_line == '\0')
 912                                 next_line = NULL;
 913                 }
 914 
 915                 pos = skip_spaces(pos);
 916                 extent.first = simple_strtoul(pos, &pos, 10);
 917                 if (!isspace(*pos))
 918                         goto out;
 919 
 920                 pos = skip_spaces(pos);
 921                 extent.lower_first = simple_strtoul(pos, &pos, 10);
 922                 if (!isspace(*pos))
 923                         goto out;
 924 
 925                 pos = skip_spaces(pos);
 926                 extent.count = simple_strtoul(pos, &pos, 10);
 927                 if (*pos && !isspace(*pos))
 928                         goto out;
 929 
 930                 /* Verify there is not trailing junk on the line */
 931                 pos = skip_spaces(pos);
 932                 if (*pos != '\0')
 933                         goto out;
 934 
 935                 /* Verify we have been given valid starting values */
 936                 if ((extent.first == (u32) -1) ||
 937                     (extent.lower_first == (u32) -1))
 938                         goto out;
 939 
 940                 /* Verify count is not zero and does not cause the
 941                  * extent to wrap
 942                  */
 943                 if ((extent.first + extent.count) <= extent.first)
 944                         goto out;
 945                 if ((extent.lower_first + extent.count) <=
 946                      extent.lower_first)
 947                         goto out;
 948 
 949                 /* Do the ranges in extent overlap any previous extents? */
 950                 if (mappings_overlap(&new_map, &extent))
 951                         goto out;
 952 
 953                 if ((new_map.nr_extents + 1) == UID_GID_MAP_MAX_EXTENTS &&
 954                     (next_line != NULL))
 955                         goto out;
 956 
 957                 ret = insert_extent(&new_map, &extent);
 958                 if (ret < 0)
 959                         goto out;
 960                 ret = -EINVAL;
 961         }
 962         /* Be very certaint the new map actually exists */
 963         if (new_map.nr_extents == 0)
 964                 goto out;
 965 
 966         ret = -EPERM;
 967         /* Validate the user is allowed to use user id's mapped to. */
 968         if (!new_idmap_permitted(file, ns, cap_setid, &new_map))
 969                 goto out;
 970 
 971         ret = -EPERM;
 972         /* Map the lower ids from the parent user namespace to the
 973          * kernel global id space.
 974          */
 975         for (idx = 0; idx < new_map.nr_extents; idx++) {
 976                 struct uid_gid_extent *e;
 977                 u32 lower_first;
 978 
 979                 if (new_map.nr_extents <= UID_GID_MAP_MAX_BASE_EXTENTS)
 980                         e = &new_map.extent[idx];
 981                 else
 982                         e = &new_map.forward[idx];
 983 
 984                 lower_first = map_id_range_down(parent_map,
 985                                                 e->lower_first,
 986                                                 e->count);
 987 
 988                 /* Fail if we can not map the specified extent to
 989                  * the kernel global id space.
 990                  */
 991                 if (lower_first == (u32) -1)
 992                         goto out;
 993 
 994                 e->lower_first = lower_first;
 995         }
 996 
 997         /*
 998          * If we want to use binary search for lookup, this clones the extent
 999          * array and sorts both copies.
1000          */
1001         ret = sort_idmaps(&new_map);
1002         if (ret < 0)
1003                 goto out;
1004 
1005         /* Install the map */
1006         if (new_map.nr_extents <= UID_GID_MAP_MAX_BASE_EXTENTS) {
1007                 memcpy(map->extent, new_map.extent,
1008                        new_map.nr_extents * sizeof(new_map.extent[0]));
1009         } else {
1010                 map->forward = new_map.forward;
1011                 map->reverse = new_map.reverse;
1012         }
1013         smp_wmb();
1014         map->nr_extents = new_map.nr_extents;
1015 
1016         *ppos = count;
1017         ret = count;
1018 out:
1019         if (ret < 0 && new_map.nr_extents > UID_GID_MAP_MAX_BASE_EXTENTS) {
1020                 kfree(new_map.forward);
1021                 kfree(new_map.reverse);
1022                 map->forward = NULL;
1023                 map->reverse = NULL;
1024                 map->nr_extents = 0;
1025         }
1026 
1027         mutex_unlock(&userns_state_mutex);
1028         kfree(kbuf);
1029         return ret;
1030 }
1031 
1032 ssize_t proc_uid_map_write(struct file *file, const char __user *buf,
1033                            size_t size, loff_t *ppos)
1034 {
1035         struct seq_file *seq = file->private_data;
1036         struct user_namespace *ns = seq->private;
1037         struct user_namespace *seq_ns = seq_user_ns(seq);
1038 
1039         if (!ns->parent)
1040                 return -EPERM;
1041 
1042         if ((seq_ns != ns) && (seq_ns != ns->parent))
1043                 return -EPERM;
1044 
1045         return map_write(file, buf, size, ppos, CAP_SETUID,
1046                          &ns->uid_map, &ns->parent->uid_map);
1047 }
1048 
1049 ssize_t proc_gid_map_write(struct file *file, const char __user *buf,
1050                            size_t size, loff_t *ppos)
1051 {
1052         struct seq_file *seq = file->private_data;
1053         struct user_namespace *ns = seq->private;
1054         struct user_namespace *seq_ns = seq_user_ns(seq);
1055 
1056         if (!ns->parent)
1057                 return -EPERM;
1058 
1059         if ((seq_ns != ns) && (seq_ns != ns->parent))
1060                 return -EPERM;
1061 
1062         return map_write(file, buf, size, ppos, CAP_SETGID,
1063                          &ns->gid_map, &ns->parent->gid_map);
1064 }
1065 
1066 ssize_t proc_projid_map_write(struct file *file, const char __user *buf,
1067                               size_t size, loff_t *ppos)
1068 {
1069         struct seq_file *seq = file->private_data;
1070         struct user_namespace *ns = seq->private;
1071         struct user_namespace *seq_ns = seq_user_ns(seq);
1072 
1073         if (!ns->parent)
1074                 return -EPERM;
1075 
1076         if ((seq_ns != ns) && (seq_ns != ns->parent))
1077                 return -EPERM;
1078 
1079         /* Anyone can set any valid project id no capability needed */
1080         return map_write(file, buf, size, ppos, -1,
1081                          &ns->projid_map, &ns->parent->projid_map);
1082 }
1083 
1084 static bool new_idmap_permitted(const struct file *file,
1085                                 struct user_namespace *ns, int cap_setid,
1086                                 struct uid_gid_map *new_map)
1087 {
1088         const struct cred *cred = file->f_cred;
1089         /* Don't allow mappings that would allow anything that wouldn't
1090          * be allowed without the establishment of unprivileged mappings.
1091          */
1092         if ((new_map->nr_extents == 1) && (new_map->extent[0].count == 1) &&
1093             uid_eq(ns->owner, cred->euid)) {
1094                 u32 id = new_map->extent[0].lower_first;
1095                 if (cap_setid == CAP_SETUID) {
1096                         kuid_t uid = make_kuid(ns->parent, id);
1097                         if (uid_eq(uid, cred->euid))
1098                                 return true;
1099                 } else if (cap_setid == CAP_SETGID) {
1100                         kgid_t gid = make_kgid(ns->parent, id);
1101                         if (!(ns->flags & USERNS_SETGROUPS_ALLOWED) &&
1102                             gid_eq(gid, cred->egid))
1103                                 return true;
1104                 }
1105         }
1106 
1107         /* Allow anyone to set a mapping that doesn't require privilege */
1108         if (!cap_valid(cap_setid))
1109                 return true;
1110 
1111         /* Allow the specified ids if we have the appropriate capability
1112          * (CAP_SETUID or CAP_SETGID) over the parent user namespace.
1113          * And the opener of the id file also had the approprpiate capability.
1114          */
1115         if (ns_capable(ns->parent, cap_setid) &&
1116             file_ns_capable(file, ns->parent, cap_setid))
1117                 return true;
1118 
1119         return false;
1120 }
1121 
1122 int proc_setgroups_show(struct seq_file *seq, void *v)
1123 {
1124         struct user_namespace *ns = seq->private;
1125         unsigned long userns_flags = READ_ONCE(ns->flags);
1126 
1127         seq_printf(seq, "%s\n",
1128                    (userns_flags & USERNS_SETGROUPS_ALLOWED) ?
1129                    "allow" : "deny");
1130         return 0;
1131 }
1132 
1133 ssize_t proc_setgroups_write(struct file *file, const char __user *buf,
1134                              size_t count, loff_t *ppos)
1135 {
1136         struct seq_file *seq = file->private_data;
1137         struct user_namespace *ns = seq->private;
1138         char kbuf[8], *pos;
1139         bool setgroups_allowed;
1140         ssize_t ret;
1141 
1142         /* Only allow a very narrow range of strings to be written */
1143         ret = -EINVAL;
1144         if ((*ppos != 0) || (count >= sizeof(kbuf)))
1145                 goto out;
1146 
1147         /* What was written? */
1148         ret = -EFAULT;
1149         if (copy_from_user(kbuf, buf, count))
1150                 goto out;
1151         kbuf[count] = '\0';
1152         pos = kbuf;
1153 
1154         /* What is being requested? */
1155         ret = -EINVAL;
1156         if (strncmp(pos, "allow", 5) == 0) {
1157                 pos += 5;
1158                 setgroups_allowed = true;
1159         }
1160         else if (strncmp(pos, "deny", 4) == 0) {
1161                 pos += 4;
1162                 setgroups_allowed = false;
1163         }
1164         else
1165                 goto out;
1166 
1167         /* Verify there is not trailing junk on the line */
1168         pos = skip_spaces(pos);
1169         if (*pos != '\0')
1170                 goto out;
1171 
1172         ret = -EPERM;
1173         mutex_lock(&userns_state_mutex);
1174         if (setgroups_allowed) {
1175                 /* Enabling setgroups after setgroups has been disabled
1176                  * is not allowed.
1177                  */
1178                 if (!(ns->flags & USERNS_SETGROUPS_ALLOWED))
1179                         goto out_unlock;
1180         } else {
1181                 /* Permanently disabling setgroups after setgroups has
1182                  * been enabled by writing the gid_map is not allowed.
1183                  */
1184                 if (ns->gid_map.nr_extents != 0)
1185                         goto out_unlock;
1186                 ns->flags &= ~USERNS_SETGROUPS_ALLOWED;
1187         }
1188         mutex_unlock(&userns_state_mutex);
1189 
1190         /* Report a successful write */
1191         *ppos = count;
1192         ret = count;
1193 out:
1194         return ret;
1195 out_unlock:
1196         mutex_unlock(&userns_state_mutex);
1197         goto out;
1198 }
1199 
1200 bool userns_may_setgroups(const struct user_namespace *ns)
1201 {
1202         bool allowed;
1203 
1204         mutex_lock(&userns_state_mutex);
1205         /* It is not safe to use setgroups until a gid mapping in
1206          * the user namespace has been established.
1207          */
1208         allowed = ns->gid_map.nr_extents != 0;
1209         /* Is setgroups allowed? */
1210         allowed = allowed && (ns->flags & USERNS_SETGROUPS_ALLOWED);
1211         mutex_unlock(&userns_state_mutex);
1212 
1213         return allowed;
1214 }
1215 
1216 /*
1217  * Returns true if @child is the same namespace or a descendant of
1218  * @ancestor.
1219  */
1220 bool in_userns(const struct user_namespace *ancestor,
1221                const struct user_namespace *child)
1222 {
1223         const struct user_namespace *ns;
1224         for (ns = child; ns->level > ancestor->level; ns = ns->parent)
1225                 ;
1226         return (ns == ancestor);
1227 }
1228 
1229 bool current_in_userns(const struct user_namespace *target_ns)
1230 {
1231         return in_userns(target_ns, current_user_ns());
1232 }
1233 EXPORT_SYMBOL(current_in_userns);
1234 
1235 static inline struct user_namespace *to_user_ns(struct ns_common *ns)
1236 {
1237         return container_of(ns, struct user_namespace, ns);
1238 }
1239 
1240 static struct ns_common *userns_get(struct task_struct *task)
1241 {
1242         struct user_namespace *user_ns;
1243 
1244         rcu_read_lock();
1245         user_ns = get_user_ns(__task_cred(task)->user_ns);
1246         rcu_read_unlock();
1247 
1248         return user_ns ? &user_ns->ns : NULL;
1249 }
1250 
1251 static void userns_put(struct ns_common *ns)
1252 {
1253         put_user_ns(to_user_ns(ns));
1254 }
1255 
1256 static int userns_install(struct nsproxy *nsproxy, struct ns_common *ns)
1257 {
1258         struct user_namespace *user_ns = to_user_ns(ns);
1259         struct cred *cred;
1260 
1261         /* Don't allow gaining capabilities by reentering
1262          * the same user namespace.
1263          */
1264         if (user_ns == current_user_ns())
1265                 return -EINVAL;
1266 
1267         /* Tasks that share a thread group must share a user namespace */
1268         if (!thread_group_empty(current))
1269                 return -EINVAL;
1270 
1271         if (current->fs->users != 1)
1272                 return -EINVAL;
1273 
1274         if (!ns_capable(user_ns, CAP_SYS_ADMIN))
1275                 return -EPERM;
1276 
1277         cred = prepare_creds();
1278         if (!cred)
1279                 return -ENOMEM;
1280 
1281         put_user_ns(cred->user_ns);
1282         set_cred_user_ns(cred, get_user_ns(user_ns));
1283 
1284         return commit_creds(cred);
1285 }
1286 
1287 struct ns_common *ns_get_owner(struct ns_common *ns)
1288 {
1289         struct user_namespace *my_user_ns = current_user_ns();
1290         struct user_namespace *owner, *p;
1291 
1292         /* See if the owner is in the current user namespace */
1293         owner = p = ns->ops->owner(ns);
1294         for (;;) {
1295                 if (!p)
1296                         return ERR_PTR(-EPERM);
1297                 if (p == my_user_ns)
1298                         break;
1299                 p = p->parent;
1300         }
1301 
1302         return &get_user_ns(owner)->ns;
1303 }
1304 
1305 static struct user_namespace *userns_owner(struct ns_common *ns)
1306 {
1307         return to_user_ns(ns)->parent;
1308 }
1309 
1310 const struct proc_ns_operations userns_operations = {
1311         .name           = "user",
1312         .type           = CLONE_NEWUSER,
1313         .get            = userns_get,
1314         .put            = userns_put,
1315         .install        = userns_install,
1316         .owner          = userns_owner,
1317         .get_parent     = ns_get_owner,
1318 };
1319 
1320 static __init int user_namespaces_init(void)
1321 {
1322         user_ns_cachep = KMEM_CACHE(user_namespace, SLAB_PANIC);
1323         return 0;
1324 }
1325 subsys_initcall(user_namespaces_init);
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root/kernel/user_namespace.c

DEFINITIONS
