kernel/cred.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /* Task credentials management - see Documentation/security/credentials.rst
   3  *
   4  * Copyright (C) 2008 Red Hat, Inc. All Rights Reserved.
   5  * Written by David Howells (dhowells@redhat.com)
   6  */
   7
   8 #define pr_fmt(fmt) "CRED: " fmt
   9
  10 #include <linux/export.h>
  11 #include <linux/cred.h>
  12 #include <linux/slab.h>
  13 #include <linux/sched.h>
  14 #include <linux/sched/coredump.h>
  15 #include <linux/key.h>
  16 #include <linux/keyctl.h>
  17 #include <linux/init_task.h>
  18 #include <linux/security.h>
  19 #include <linux/binfmts.h>
  20 #include <linux/cn_proc.h>
  21 #include <linux/uidgid.h>
  22
  23 #if 0
  24 #define kdebug(FMT, ...)                                                \
  25         printk("[%-5.5s%5u] " FMT "\n",                                 \
  26                current->comm, current->pid, ##__VA_ARGS__)
  27 #else
  28 #define kdebug(FMT, ...)                                                \
  29 do {                                                                    \
  30         if (0)                                                          \
  31                 no_printk("[%-5.5s%5u] " FMT "\n",                      \
  32                           current->comm, current->pid, ##__VA_ARGS__);  \
  33 } while (0)
  34 #endif
  35
  36 static struct kmem_cache *cred_jar;
  37
  38 /* init to 2 - one for init_task, one to ensure it is never freed */
  39 static struct group_info init_groups = { .usage = ATOMIC_INIT(2) };
  40
  41 /*
  42  * The initial credentials for the initial task
  43  */
  44 struct cred init_cred = {
  45         .usage                  = ATOMIC_INIT(4),
  46         .uid                    = GLOBAL_ROOT_UID,
  47         .gid                    = GLOBAL_ROOT_GID,
  48         .suid                   = GLOBAL_ROOT_UID,
  49         .sgid                   = GLOBAL_ROOT_GID,
  50         .euid                   = GLOBAL_ROOT_UID,
  51         .egid                   = GLOBAL_ROOT_GID,
  52         .fsuid                  = GLOBAL_ROOT_UID,
  53         .fsgid                  = GLOBAL_ROOT_GID,
  54         .securebits             = SECUREBITS_DEFAULT,
  55         .cap_inheritable        = CAP_EMPTY_SET,
  56         .cap_permitted          = CAP_FULL_SET,
  57         .cap_effective          = CAP_FULL_SET,
  58         .cap_bset               = CAP_FULL_SET,
  59         .user                   = INIT_USER,
  60         .user_ns                = &init_user_ns,
  61         .group_info             = &init_groups,
  62         .ucounts                = &init_ucounts,
  63 };
  64
  65 /*
  66  * The RCU callback to actually dispose of a set of credentials
  67  */
  68 static void put_cred_rcu(struct rcu_head *rcu)
  69 {
  70         struct cred *cred = container_of(rcu, struct cred, rcu);
  71
  72         kdebug("put_cred_rcu(%p)", cred);
  73
  74         if (atomic_long_read(&cred->usage) != 0)
  75                 panic("CRED: put_cred_rcu() sees %p with usage %ld\n",
  76                       cred, atomic_long_read(&cred->usage));
  77
  78         security_cred_free(cred);
  79         key_put(cred->session_keyring);
  80         key_put(cred->process_keyring);
  81         key_put(cred->thread_keyring);
  82         key_put(cred->request_key_auth);
  83         if (cred->group_info)
  84                 put_group_info(cred->group_info);
  85         free_uid(cred->user);
  86         if (cred->ucounts)
  87                 put_ucounts(cred->ucounts);
  88         put_user_ns(cred->user_ns);
  89         kmem_cache_free(cred_jar, cred);
  90 }
  91
  92 /**
  93  * __put_cred - Destroy a set of credentials
  94  * @cred: The record to release
  95  *
  96  * Destroy a set of credentials on which no references remain.
  97  */
  98 void __put_cred(struct cred *cred)
  99 {
 100         kdebug("__put_cred(%p{%ld})", cred,
 101                atomic_long_read(&cred->usage));
 102
 103         BUG_ON(atomic_long_read(&cred->usage) != 0);
 104         BUG_ON(cred == current->cred);
 105         BUG_ON(cred == current->real_cred);
 106
 107         if (cred->non_rcu)
 108                 put_cred_rcu(&cred->rcu);
 109         else
 110                 call_rcu(&cred->rcu, put_cred_rcu);
 111 }
 112 EXPORT_SYMBOL(__put_cred);
 113
 114 /*
 115  * Clean up a task's credentials when it exits
 116  */
 117 void exit_creds(struct task_struct *tsk)
 118 {
 119         struct cred *cred;
 120
 121         kdebug("exit_creds(%u,%p,%p,{%ld})", tsk->pid, tsk->real_cred, tsk->cred,
 122                atomic_long_read(&tsk->cred->usage));
 123
 124         cred = (struct cred *) tsk->real_cred;
 125         tsk->real_cred = NULL;
 126         put_cred(cred);
 127
 128         cred = (struct cred *) tsk->cred;
 129         tsk->cred = NULL;
 130         put_cred(cred);
 131
 132 #ifdef CONFIG_KEYS_REQUEST_CACHE
 133         key_put(tsk->cached_requested_key);
 134         tsk->cached_requested_key = NULL;
 135 #endif
 136 }
 137
 138 /**
 139  * get_task_cred - Get another task's objective credentials
 140  * @task: The task to query
 141  *
 142  * Get the objective credentials of a task, pinning them so that they can't go
 143  * away.  Accessing a task's credentials directly is not permitted.
 144  *
 145  * The caller must also make sure task doesn't get deleted, either by holding a
 146  * ref on task or by holding tasklist_lock to prevent it from being unlinked.
 147  */
 148 const struct cred *get_task_cred(struct task_struct *task)
 149 {
 150         const struct cred *cred;
 151
 152         rcu_read_lock();
 153
 154         do {
 155                 cred = __task_cred((task));
 156                 BUG_ON(!cred);
 157         } while (!get_cred_rcu(cred));
 158
 159         rcu_read_unlock();
 160         return cred;
 161 }
 162 EXPORT_SYMBOL(get_task_cred);
 163
 164 /*
 165  * Allocate blank credentials, such that the credentials can be filled in at a
 166  * later date without risk of ENOMEM.
 167  */
 168 struct cred *cred_alloc_blank(void)
 169 {
 170         struct cred *new;
 171
 172         new = kmem_cache_zalloc(cred_jar, GFP_KERNEL);
 173         if (!new)
 174                 return NULL;
 175
 176         atomic_long_set(&new->usage, 1);
 177         if (security_cred_alloc_blank(new, GFP_KERNEL_ACCOUNT) < 0)
 178                 goto error;
 179
 180         return new;
 181
 182 error:
 183         abort_creds(new);
 184         return NULL;
 185 }
 186
 187 /**
 188  * prepare_creds - Prepare a new set of credentials for modification
 189  *
 190  * Prepare a new set of task credentials for modification.  A task's creds
 191  * shouldn't generally be modified directly, therefore this function is used to
 192  * prepare a new copy, which the caller then modifies and then commits by
 193  * calling commit_creds().
 194  *
 195  * Preparation involves making a copy of the objective creds for modification.
 196  *
 197  * Returns a pointer to the new creds-to-be if successful, NULL otherwise.
 198  *
 199  * Call commit_creds() or abort_creds() to clean up.
 200  */
 201 struct cred *prepare_creds(void)
 202 {
 203         struct task_struct *task = current;
 204         const struct cred *old;
 205         struct cred *new;
 206
 207         new = kmem_cache_alloc(cred_jar, GFP_KERNEL);
 208         if (!new)
 209                 return NULL;
 210
 211         kdebug("prepare_creds() alloc %p", new);
 212
 213         old = task->cred;
 214         memcpy(new, old, sizeof(struct cred));
 215
 216         new->non_rcu = 0;
 217         atomic_long_set(&new->usage, 1);
 218         get_group_info(new->group_info);
 219         get_uid(new->user);
 220         get_user_ns(new->user_ns);
 221
 222 #ifdef CONFIG_KEYS
 223         key_get(new->session_keyring);
 224         key_get(new->process_keyring);
 225         key_get(new->thread_keyring);
 226         key_get(new->request_key_auth);
 227 #endif
 228
 229 #ifdef CONFIG_SECURITY
 230         new->security = NULL;
 231 #endif
 232
 233         new->ucounts = get_ucounts(new->ucounts);
 234         if (!new->ucounts)
 235                 goto error;
 236
 237         if (security_prepare_creds(new, old, GFP_KERNEL_ACCOUNT) < 0)
 238                 goto error;
 239
 240         return new;
 241
 242 error:
 243         abort_creds(new);
 244         return NULL;
 245 }
 246 EXPORT_SYMBOL(prepare_creds);
 247
 248 /*
 249  * Prepare credentials for current to perform an execve()
 250  * - The caller must hold ->cred_guard_mutex
 251  */
 252 struct cred *prepare_exec_creds(void)
 253 {
 254         struct cred *new;
 255
 256         new = prepare_creds();
 257         if (!new)
 258                 return new;
 259
 260 #ifdef CONFIG_KEYS
 261         /* newly exec'd tasks don't get a thread keyring */
 262         key_put(new->thread_keyring);
 263         new->thread_keyring = NULL;
 264
 265         /* inherit the session keyring; new process keyring */
 266         key_put(new->process_keyring);
 267         new->process_keyring = NULL;
 268 #endif
 269
 270         new->suid = new->fsuid = new->euid;
 271         new->sgid = new->fsgid = new->egid;
 272
 273         return new;
 274 }
 275
 276 /*
 277  * Copy credentials for the new process created by fork()
 278  *
 279  * We share if we can, but under some circumstances we have to generate a new
 280  * set.
 281  *
 282  * The new process gets the current process's subjective credentials as its
 283  * objective and subjective credentials
 284  */
 285 int copy_creds(struct task_struct *p, unsigned long clone_flags)
 286 {
 287         struct cred *new;
 288         int ret;
 289
 290 #ifdef CONFIG_KEYS_REQUEST_CACHE
 291         p->cached_requested_key = NULL;
 292 #endif
 293
 294         if (
 295 #ifdef CONFIG_KEYS
 296                 !p->cred->thread_keyring &&
 297 #endif
 298                 clone_flags & CLONE_THREAD
 299             ) {
 300                 p->real_cred = get_cred(p->cred);
 301                 get_cred(p->cred);
 302                 kdebug("share_creds(%p{%ld})",
 303                        p->cred, atomic_long_read(&p->cred->usage));
 304                 inc_rlimit_ucounts(task_ucounts(p), UCOUNT_RLIMIT_NPROC, 1);
 305                 return 0;
 306         }
 307
 308         new = prepare_creds();
 309         if (!new)
 310                 return -ENOMEM;
 311
 312         if (clone_flags & CLONE_NEWUSER) {
 313                 ret = create_user_ns(new);
 314                 if (ret < 0)
 315                         goto error_put;
 316                 ret = set_cred_ucounts(new);
 317                 if (ret < 0)
 318                         goto error_put;
 319         }
 320
 321 #ifdef CONFIG_KEYS
 322         /* new threads get their own thread keyrings if their parent already
 323          * had one */
 324         if (new->thread_keyring) {
 325                 key_put(new->thread_keyring);
 326                 new->thread_keyring = NULL;
 327                 if (clone_flags & CLONE_THREAD)
 328                         install_thread_keyring_to_cred(new);
 329         }
 330
 331         /* The process keyring is only shared between the threads in a process;
 332          * anything outside of those threads doesn't inherit.
 333          */
 334         if (!(clone_flags & CLONE_THREAD)) {
 335                 key_put(new->process_keyring);
 336                 new->process_keyring = NULL;
 337         }
 338 #endif
 339
 340         p->cred = p->real_cred = get_cred(new);
 341         inc_rlimit_ucounts(task_ucounts(p), UCOUNT_RLIMIT_NPROC, 1);
 342         return 0;
 343
 344 error_put:
 345         put_cred(new);
 346         return ret;
 347 }
 348
 349 static bool cred_cap_issubset(const struct cred *set, const struct cred *subset)
 350 {
 351         const struct user_namespace *set_ns = set->user_ns;
 352         const struct user_namespace *subset_ns = subset->user_ns;
 353
 354         /* If the two credentials are in the same user namespace see if
 355          * the capabilities of subset are a subset of set.
 356          */
 357         if (set_ns == subset_ns)
 358                 return cap_issubset(subset->cap_permitted, set->cap_permitted);
 359
 360         /* The credentials are in a different user namespaces
 361          * therefore one is a subset of the other only if a set is an
 362          * ancestor of subset and set->euid is owner of subset or one
 363          * of subsets ancestors.
 364          */
 365         for (;subset_ns != &init_user_ns; subset_ns = subset_ns->parent) {
 366                 if ((set_ns == subset_ns->parent)  &&
 367                     uid_eq(subset_ns->owner, set->euid))
 368                         return true;
 369         }
 370
 371         return false;
 372 }
 373
 374 /**
 375  * commit_creds - Install new credentials upon the current task
 376  * @new: The credentials to be assigned
 377  *
 378  * Install a new set of credentials to the current task, using RCU to replace
 379  * the old set.  Both the objective and the subjective credentials pointers are
 380  * updated.  This function may not be called if the subjective credentials are
 381  * in an overridden state.
 382  *
 383  * This function eats the caller's reference to the new credentials.
 384  *
 385  * Always returns 0 thus allowing this function to be tail-called at the end
 386  * of, say, sys_setgid().
 387  */
 388 int commit_creds(struct cred *new)
 389 {
 390         struct task_struct *task = current;
 391         const struct cred *old = task->real_cred;
 392
 393         kdebug("commit_creds(%p{%ld})", new,
 394                atomic_long_read(&new->usage));
 395
 396         BUG_ON(task->cred != old);
 397         BUG_ON(atomic_long_read(&new->usage) < 1);
 398
 399         get_cred(new); /* we will require a ref for the subj creds too */
 400
 401         /* dumpability changes */
 402         if (!uid_eq(old->euid, new->euid) ||
 403             !gid_eq(old->egid, new->egid) ||
 404             !uid_eq(old->fsuid, new->fsuid) ||
 405             !gid_eq(old->fsgid, new->fsgid) ||
 406             !cred_cap_issubset(old, new)) {
 407                 if (task->mm)
 408                         set_dumpable(task->mm, suid_dumpable);
 409                 task->pdeath_signal = 0;
 410                 /*
 411                  * If a task drops privileges and becomes nondumpable,
 412                  * the dumpability change must become visible before
 413                  * the credential change; otherwise, a __ptrace_may_access()
 414                  * racing with this change may be able to attach to a task it
 415                  * shouldn't be able to attach to (as if the task had dropped
 416                  * privileges without becoming nondumpable).
 417                  * Pairs with a read barrier in __ptrace_may_access().
 418                  */
 419                 smp_wmb();
 420         }
 421
 422         /* alter the thread keyring */
 423         if (!uid_eq(new->fsuid, old->fsuid))
 424                 key_fsuid_changed(new);
 425         if (!gid_eq(new->fsgid, old->fsgid))
 426                 key_fsgid_changed(new);
 427
 428         /* do it
 429          * RLIMIT_NPROC limits on user->processes have already been checked
 430          * in set_user().
 431          */
 432         if (new->user != old->user || new->user_ns != old->user_ns)
 433                 inc_rlimit_ucounts(new->ucounts, UCOUNT_RLIMIT_NPROC, 1);
 434         rcu_assign_pointer(task->real_cred, new);
 435         rcu_assign_pointer(task->cred, new);
 436         if (new->user != old->user || new->user_ns != old->user_ns)
 437                 dec_rlimit_ucounts(old->ucounts, UCOUNT_RLIMIT_NPROC, 1);
 438
 439         /* send notifications */
 440         if (!uid_eq(new->uid,   old->uid)  ||
 441             !uid_eq(new->euid,  old->euid) ||
 442             !uid_eq(new->suid,  old->suid) ||
 443             !uid_eq(new->fsuid, old->fsuid))
 444                 proc_id_connector(task, PROC_EVENT_UID);
 445
 446         if (!gid_eq(new->gid,   old->gid)  ||
 447             !gid_eq(new->egid,  old->egid) ||
 448             !gid_eq(new->sgid,  old->sgid) ||
 449             !gid_eq(new->fsgid, old->fsgid))
 450                 proc_id_connector(task, PROC_EVENT_GID);
 451
 452         /* release the old obj and subj refs both */
 453         put_cred(old);
 454         put_cred(old);
 455         return 0;
 456 }
 457 EXPORT_SYMBOL(commit_creds);
 458
 459 /**
 460  * abort_creds - Discard a set of credentials and unlock the current task
 461  * @new: The credentials that were going to be applied
 462  *
 463  * Discard a set of credentials that were under construction and unlock the
 464  * current task.
 465  */
 466 void abort_creds(struct cred *new)
 467 {
 468         kdebug("abort_creds(%p{%ld})", new,
 469                atomic_long_read(&new->usage));
 470
 471         BUG_ON(atomic_long_read(&new->usage) < 1);
 472         put_cred(new);
 473 }
 474 EXPORT_SYMBOL(abort_creds);
 475
 476 /**
 477  * override_creds - Override the current process's subjective credentials
 478  * @new: The credentials to be assigned
 479  *
 480  * Install a set of temporary override subjective credentials on the current
 481  * process, returning the old set for later reversion.
 482  */
 483 const struct cred *override_creds(const struct cred *new)
 484 {
 485         const struct cred *old = current->cred;
 486
 487         kdebug("override_creds(%p{%ld})", new,
 488                atomic_long_read(&new->usage));
 489
 490         /*
 491          * NOTE! This uses 'get_new_cred()' rather than 'get_cred()'.
 492          *
 493          * That means that we do not clear the 'non_rcu' flag, since
 494          * we are only installing the cred into the thread-synchronous
 495          * '->cred' pointer, not the '->real_cred' pointer that is
 496          * visible to other threads under RCU.
 497          */
 498         get_new_cred((struct cred *)new);
 499         rcu_assign_pointer(current->cred, new);
 500
 501         kdebug("override_creds() = %p{%ld}", old,
 502                atomic_long_read(&old->usage));
 503         return old;
 504 }
 505 EXPORT_SYMBOL(override_creds);
 506
 507 /**
 508  * revert_creds - Revert a temporary subjective credentials override
 509  * @old: The credentials to be restored
 510  *
 511  * Revert a temporary set of override subjective credentials to an old set,
 512  * discarding the override set.
 513  */
 514 void revert_creds(const struct cred *old)
 515 {
 516         const struct cred *override = current->cred;
 517
 518         kdebug("revert_creds(%p{%ld})", old,
 519                atomic_long_read(&old->usage));
 520
 521         rcu_assign_pointer(current->cred, old);
 522         put_cred(override);
 523 }
 524 EXPORT_SYMBOL(revert_creds);
 525
 526 /**
 527  * cred_fscmp - Compare two credentials with respect to filesystem access.
 528  * @a: The first credential
 529  * @b: The second credential
 530  *
 531  * cred_cmp() will return zero if both credentials have the same
 532  * fsuid, fsgid, and supplementary groups.  That is, if they will both
 533  * provide the same access to files based on mode/uid/gid.
 534  * If the credentials are different, then either -1 or 1 will
 535  * be returned depending on whether @a comes before or after @b
 536  * respectively in an arbitrary, but stable, ordering of credentials.
 537  *
 538  * Return: -1, 0, or 1 depending on comparison
 539  */
 540 int cred_fscmp(const struct cred *a, const struct cred *b)
 541 {
 542         struct group_info *ga, *gb;
 543         int g;
 544
 545         if (a == b)
 546                 return 0;
 547         if (uid_lt(a->fsuid, b->fsuid))
 548                 return -1;
 549         if (uid_gt(a->fsuid, b->fsuid))
 550                 return 1;
 551
 552         if (gid_lt(a->fsgid, b->fsgid))
 553                 return -1;
 554         if (gid_gt(a->fsgid, b->fsgid))
 555                 return 1;
 556
 557         ga = a->group_info;
 558         gb = b->group_info;
 559         if (ga == gb)
 560                 return 0;
 561         if (ga == NULL)
 562                 return -1;
 563         if (gb == NULL)
 564                 return 1;
 565         if (ga->ngroups < gb->ngroups)
 566                 return -1;
 567         if (ga->ngroups > gb->ngroups)
 568                 return 1;
 569
 570         for (g = 0; g < ga->ngroups; g++) {
 571                 if (gid_lt(ga->gid[g], gb->gid[g]))
 572                         return -1;
 573                 if (gid_gt(ga->gid[g], gb->gid[g]))
 574                         return 1;
 575         }
 576         return 0;
 577 }
 578 EXPORT_SYMBOL(cred_fscmp);
 579
 580 int set_cred_ucounts(struct cred *new)
 581 {
 582         struct ucounts *new_ucounts, *old_ucounts = new->ucounts;
 583
 584         /*
 585          * This optimization is needed because alloc_ucounts() uses locks
 586          * for table lookups.
 587          */
 588         if (old_ucounts->ns == new->user_ns && uid_eq(old_ucounts->uid, new->uid))
 589                 return 0;
 590
 591         if (!(new_ucounts = alloc_ucounts(new->user_ns, new->uid)))
 592                 return -EAGAIN;
 593
 594         new->ucounts = new_ucounts;
 595         put_ucounts(old_ucounts);
 596
 597         return 0;
 598 }
 599
 600 /*
 601  * initialise the credentials stuff
 602  */
 603 void __init cred_init(void)
 604 {
 605         /* allocate a slab in which we can store credentials */
 606         cred_jar = kmem_cache_create("cred_jar", sizeof(struct cred), 0,
 607                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT, NULL);
 608 }
 609
 610 /**
 611  * prepare_kernel_cred - Prepare a set of credentials for a kernel service
 612  * @daemon: A userspace daemon to be used as a reference
 613  *
 614  * Prepare a set of credentials for a kernel service.  This can then be used to
 615  * override a task's own credentials so that work can be done on behalf of that
 616  * task that requires a different subjective context.
 617  *
 618  * @daemon is used to provide a base cred, with the security data derived from
 619  * that; if this is "&init_task", they'll be set to 0, no groups, full
 620  * capabilities, and no keys.
 621  *
 622  * The caller may change these controls afterwards if desired.
 623  *
 624  * Returns the new credentials or NULL if out of memory.
 625  */
 626 struct cred *prepare_kernel_cred(struct task_struct *daemon)
 627 {
 628         const struct cred *old;
 629         struct cred *new;
 630
 631         if (WARN_ON_ONCE(!daemon))
 632                 return NULL;
 633
 634         new = kmem_cache_alloc(cred_jar, GFP_KERNEL);
 635         if (!new)
 636                 return NULL;
 637
 638         kdebug("prepare_kernel_cred() alloc %p", new);
 639
 640         old = get_task_cred(daemon);
 641
 642         *new = *old;
 643         new->non_rcu = 0;
 644         atomic_long_set(&new->usage, 1);
 645         get_uid(new->user);
 646         get_user_ns(new->user_ns);
 647         get_group_info(new->group_info);
 648
 649 #ifdef CONFIG_KEYS
 650         new->session_keyring = NULL;
 651         new->process_keyring = NULL;
 652         new->thread_keyring = NULL;
 653         new->request_key_auth = NULL;
 654         new->jit_keyring = KEY_REQKEY_DEFL_THREAD_KEYRING;
 655 #endif
 656
 657 #ifdef CONFIG_SECURITY
 658         new->security = NULL;
 659 #endif
 660         new->ucounts = get_ucounts(new->ucounts);
 661         if (!new->ucounts)
 662                 goto error;
 663
 664         if (security_prepare_creds(new, old, GFP_KERNEL_ACCOUNT) < 0)
 665                 goto error;
 666
 667         put_cred(old);
 668         return new;
 669
 670 error:
 671         put_cred(new);
 672         put_cred(old);
 673         return NULL;
 674 }
 675 EXPORT_SYMBOL(prepare_kernel_cred);
 676
 677 /**
 678  * set_security_override - Set the security ID in a set of credentials
 679  * @new: The credentials to alter
 680  * @secid: The LSM security ID to set
 681  *
 682  * Set the LSM security ID in a set of credentials so that the subjective
 683  * security is overridden when an alternative set of credentials is used.
 684  */
 685 int set_security_override(struct cred *new, u32 secid)
 686 {
 687         return security_kernel_act_as(new, secid);
 688 }
 689 EXPORT_SYMBOL(set_security_override);
 690
 691 /**
 692  * set_security_override_from_ctx - Set the security ID in a set of credentials
 693  * @new: The credentials to alter
 694  * @secctx: The LSM security context to generate the security ID from.
 695  *
 696  * Set the LSM security ID in a set of credentials so that the subjective
 697  * security is overridden when an alternative set of credentials is used.  The
 698  * security ID is specified in string form as a security context to be
 699  * interpreted by the LSM.
 700  */
 701 int set_security_override_from_ctx(struct cred *new, const char *secctx)
 702 {
 703         u32 secid;
 704         int ret;
 705
 706         ret = security_secctx_to_secid(secctx, strlen(secctx), &secid);
 707         if (ret < 0)
 708                 return ret;
 709
 710         return set_security_override(new, secid);
 711 }
 712 EXPORT_SYMBOL(set_security_override_from_ctx);
 713
 714 /**
 715  * set_create_files_as - Set the LSM file create context in a set of credentials
 716  * @new: The credentials to alter
 717  * @inode: The inode to take the context from
 718  *
 719  * Change the LSM file creation context in a set of credentials to be the same
 720  * as the object context of the specified inode, so that the new inodes have
 721  * the same MAC context as that inode.
 722  */
 723 int set_create_files_as(struct cred *new, struct inode *inode)
 724 {
 725         if (!uid_valid(inode->i_uid) || !gid_valid(inode->i_gid))
 726                 return -EINVAL;
 727         new->fsuid = inode->i_uid;
 728         new->fsgid = inode->i_gid;
 729         return security_kernel_create_files_as(new, inode);
 730 }
 731 EXPORT_SYMBOL(set_create_files_as);