LCOV - code coverage report
Current view: top level - kernel - cred.c (source / functions) Hit Total Coverage
Test: combined.info Lines: 201 258 77.9 %
Date: 2022-03-28 13:20:08 Functions: 13 18 72.2 %
Branches: 70 144 48.6 %

           Branch data     Line data    Source code
       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                 :            : #include <linux/export.h>
       8                 :            : #include <linux/cred.h>
       9                 :            : #include <linux/slab.h>
      10                 :            : #include <linux/sched.h>
      11                 :            : #include <linux/sched/coredump.h>
      12                 :            : #include <linux/key.h>
      13                 :            : #include <linux/keyctl.h>
      14                 :            : #include <linux/init_task.h>
      15                 :            : #include <linux/security.h>
      16                 :            : #include <linux/binfmts.h>
      17                 :            : #include <linux/cn_proc.h>
      18                 :            : #include <linux/uidgid.h>
      19                 :            : 
      20                 :            : #if 0
      21                 :            : #define kdebug(FMT, ...)                                                \
      22                 :            :         printk("[%-5.5s%5u] " FMT "\n",                                     \
      23                 :            :                current->comm, current->pid, ##__VA_ARGS__)
      24                 :            : #else
      25                 :            : #define kdebug(FMT, ...)                                                \
      26                 :            : do {                                                                    \
      27                 :            :         if (0)                                                          \
      28                 :            :                 no_printk("[%-5.5s%5u] " FMT "\n",                  \
      29                 :            :                           current->comm, current->pid, ##__VA_ARGS__);    \
      30                 :            : } while (0)
      31                 :            : #endif
      32                 :            : 
      33                 :            : static struct kmem_cache *cred_jar;
      34                 :            : 
      35                 :            : /* init to 2 - one for init_task, one to ensure it is never freed */
      36                 :            : struct group_info init_groups = { .usage = ATOMIC_INIT(2) };
      37                 :            : 
      38                 :            : /*
      39                 :            :  * The initial credentials for the initial task
      40                 :            :  */
      41                 :            : struct cred init_cred = {
      42                 :            :         .usage                  = ATOMIC_INIT(4),
      43                 :            : #ifdef CONFIG_DEBUG_CREDENTIALS
      44                 :            :         .subscribers            = ATOMIC_INIT(2),
      45                 :            :         .magic                  = CRED_MAGIC,
      46                 :            : #endif
      47                 :            :         .uid                    = GLOBAL_ROOT_UID,
      48                 :            :         .gid                    = GLOBAL_ROOT_GID,
      49                 :            :         .suid                   = GLOBAL_ROOT_UID,
      50                 :            :         .sgid                   = GLOBAL_ROOT_GID,
      51                 :            :         .euid                   = GLOBAL_ROOT_UID,
      52                 :            :         .egid                   = GLOBAL_ROOT_GID,
      53                 :            :         .fsuid                  = GLOBAL_ROOT_UID,
      54                 :            :         .fsgid                  = GLOBAL_ROOT_GID,
      55                 :            :         .securebits             = SECUREBITS_DEFAULT,
      56                 :            :         .cap_inheritable        = CAP_EMPTY_SET,
      57                 :            :         .cap_permitted          = CAP_FULL_SET,
      58                 :            :         .cap_effective          = CAP_FULL_SET,
      59                 :            :         .cap_bset               = CAP_FULL_SET,
      60                 :            :         .user                   = INIT_USER,
      61                 :            :         .user_ns                = &init_user_ns,
      62                 :            :         .group_info             = &init_groups,
      63                 :            : };
      64                 :            : 
      65                 :     158652 : static inline void set_cred_subscribers(struct cred *cred, int n)
      66                 :            : {
      67                 :            : #ifdef CONFIG_DEBUG_CREDENTIALS
      68                 :            :         atomic_set(&cred->subscribers, n);
      69                 :            : #endif
      70                 :     158652 : }
      71                 :            : 
      72                 :            : static inline int read_cred_subscribers(const struct cred *cred)
      73                 :            : {
      74                 :            : #ifdef CONFIG_DEBUG_CREDENTIALS
      75                 :            :         return atomic_read(&cred->subscribers);
      76                 :            : #else
      77                 :            :         return 0;
      78                 :            : #endif
      79                 :            : }
      80                 :            : 
      81                 :     481513 : static inline void alter_cred_subscribers(const struct cred *_cred, int n)
      82                 :            : {
      83                 :            : #ifdef CONFIG_DEBUG_CREDENTIALS
      84                 :            :         struct cred *cred = (struct cred *) _cred;
      85                 :            : 
      86                 :            :         atomic_add(n, &cred->subscribers);
      87                 :            : #endif
      88                 :     481513 : }
      89                 :            : 
      90                 :            : /*
      91                 :            :  * The RCU callback to actually dispose of a set of credentials
      92                 :            :  */
      93                 :     155371 : static void put_cred_rcu(struct rcu_head *rcu)
      94                 :            : {
      95                 :     155371 :         struct cred *cred = container_of(rcu, struct cred, rcu);
      96                 :            : 
      97                 :     155371 :         kdebug("put_cred_rcu(%p)", cred);
      98                 :            : 
      99                 :            : #ifdef CONFIG_DEBUG_CREDENTIALS
     100                 :            :         if (cred->magic != CRED_MAGIC_DEAD ||
     101                 :            :             atomic_read(&cred->usage) != 0 ||
     102                 :            :             read_cred_subscribers(cred) != 0)
     103                 :            :                 panic("CRED: put_cred_rcu() sees %p with"
     104                 :            :                       " mag %x, put %p, usage %d, subscr %d\n",
     105                 :            :                       cred, cred->magic, cred->put_addr,
     106                 :            :                       atomic_read(&cred->usage),
     107                 :            :                       read_cred_subscribers(cred));
     108                 :            : #else
     109         [ -  + ]:     155371 :         if (atomic_read(&cred->usage) != 0)
     110                 :          0 :                 panic("CRED: put_cred_rcu() sees %p with usage %d\n",
     111                 :            :                       cred, atomic_read(&cred->usage));
     112                 :            : #endif
     113                 :            : 
     114                 :     155371 :         security_cred_free(cred);
     115                 :     155371 :         key_put(cred->session_keyring);
     116                 :     155371 :         key_put(cred->process_keyring);
     117                 :     155371 :         key_put(cred->thread_keyring);
     118                 :     155371 :         key_put(cred->request_key_auth);
     119         [ +  - ]:     155371 :         if (cred->group_info)
     120         [ +  + ]:     155371 :                 put_group_info(cred->group_info);
     121                 :     155371 :         free_uid(cred->user);
     122                 :     155371 :         put_user_ns(cred->user_ns);
     123                 :     155371 :         kmem_cache_free(cred_jar, cred);
     124                 :     155371 : }
     125                 :            : 
     126                 :            : /**
     127                 :            :  * __put_cred - Destroy a set of credentials
     128                 :            :  * @cred: The record to release
     129                 :            :  *
     130                 :            :  * Destroy a set of credentials on which no references remain.
     131                 :            :  */
     132                 :     155653 : void __put_cred(struct cred *cred)
     133                 :            : {
     134                 :     155653 :         kdebug("__put_cred(%p{%d,%d})", cred,
     135                 :            :                atomic_read(&cred->usage),
     136                 :            :                read_cred_subscribers(cred));
     137                 :            : 
     138         [ -  + ]:     155653 :         BUG_ON(atomic_read(&cred->usage) != 0);
     139                 :            : #ifdef CONFIG_DEBUG_CREDENTIALS
     140                 :            :         BUG_ON(read_cred_subscribers(cred) != 0);
     141                 :            :         cred->magic = CRED_MAGIC_DEAD;
     142                 :            :         cred->put_addr = __builtin_return_address(0);
     143                 :            : #endif
     144         [ -  + ]:     155653 :         BUG_ON(cred == current->cred);
     145         [ -  + ]:     155653 :         BUG_ON(cred == current->real_cred);
     146                 :            : 
     147         [ +  + ]:     155653 :         if (cred->non_rcu)
     148                 :     101583 :                 put_cred_rcu(&cred->rcu);
     149                 :            :         else
     150                 :      54070 :                 call_rcu(&cred->rcu, put_cred_rcu);
     151                 :     155653 : }
     152                 :            : EXPORT_SYMBOL(__put_cred);
     153                 :            : 
     154                 :            : /*
     155                 :            :  * Clean up a task's credentials when it exits
     156                 :            :  */
     157                 :      13328 : void exit_creds(struct task_struct *tsk)
     158                 :            : {
     159                 :      13328 :         struct cred *cred;
     160                 :            : 
     161                 :      13328 :         kdebug("exit_creds(%u,%p,%p,{%d,%d})", tsk->pid, tsk->real_cred, tsk->cred,
     162                 :            :                atomic_read(&tsk->cred->usage),
     163                 :            :                read_cred_subscribers(tsk->cred));
     164                 :            : 
     165                 :      13328 :         cred = (struct cred *) tsk->real_cred;
     166                 :      13328 :         tsk->real_cred = NULL;
     167                 :      13328 :         validate_creds(cred);
     168                 :      13328 :         alter_cred_subscribers(cred, -1);
     169                 :      13328 :         put_cred(cred);
     170                 :            : 
     171                 :      13328 :         cred = (struct cred *) tsk->cred;
     172                 :      13328 :         tsk->cred = NULL;
     173                 :      13328 :         validate_creds(cred);
     174                 :      13328 :         alter_cred_subscribers(cred, -1);
     175                 :      13328 :         put_cred(cred);
     176                 :            : 
     177                 :            : #ifdef CONFIG_KEYS_REQUEST_CACHE
     178                 :            :         key_put(tsk->cached_requested_key);
     179                 :            :         tsk->cached_requested_key = NULL;
     180                 :            : #endif
     181                 :      13328 : }
     182                 :            : 
     183                 :            : /**
     184                 :            :  * get_task_cred - Get another task's objective credentials
     185                 :            :  * @task: The task to query
     186                 :            :  *
     187                 :            :  * Get the objective credentials of a task, pinning them so that they can't go
     188                 :            :  * away.  Accessing a task's credentials directly is not permitted.
     189                 :            :  *
     190                 :            :  * The caller must also make sure task doesn't get deleted, either by holding a
     191                 :            :  * ref on task or by holding tasklist_lock to prevent it from being unlinked.
     192                 :            :  */
     193                 :       4140 : const struct cred *get_task_cred(struct task_struct *task)
     194                 :            : {
     195                 :       4140 :         const struct cred *cred;
     196                 :            : 
     197                 :       4140 :         rcu_read_lock();
     198                 :            : 
     199                 :       4140 :         do {
     200         [ -  + ]:       4140 :                 cred = __task_cred((task));
     201         [ -  + ]:       4140 :                 BUG_ON(!cred);
     202         [ -  + ]:       4140 :         } while (!get_cred_rcu(cred));
     203                 :            : 
     204                 :       4140 :         rcu_read_unlock();
     205                 :       4140 :         return cred;
     206                 :            : }
     207                 :            : EXPORT_SYMBOL(get_task_cred);
     208                 :            : 
     209                 :            : /*
     210                 :            :  * Allocate blank credentials, such that the credentials can be filled in at a
     211                 :            :  * later date without risk of ENOMEM.
     212                 :            :  */
     213                 :          0 : struct cred *cred_alloc_blank(void)
     214                 :            : {
     215                 :          0 :         struct cred *new;
     216                 :            : 
     217                 :          0 :         new = kmem_cache_zalloc(cred_jar, GFP_KERNEL);
     218         [ #  # ]:          0 :         if (!new)
     219                 :            :                 return NULL;
     220                 :            : 
     221                 :          0 :         atomic_set(&new->usage, 1);
     222                 :            : #ifdef CONFIG_DEBUG_CREDENTIALS
     223                 :            :         new->magic = CRED_MAGIC;
     224                 :            : #endif
     225                 :            : 
     226         [ #  # ]:          0 :         if (security_cred_alloc_blank(new, GFP_KERNEL_ACCOUNT) < 0)
     227                 :          0 :                 goto error;
     228                 :            : 
     229                 :            :         return new;
     230                 :            : 
     231                 :            : error:
     232                 :          0 :         abort_creds(new);
     233                 :          0 :         return NULL;
     234                 :            : }
     235                 :            : 
     236                 :            : /**
     237                 :            :  * prepare_creds - Prepare a new set of credentials for modification
     238                 :            :  *
     239                 :            :  * Prepare a new set of task credentials for modification.  A task's creds
     240                 :            :  * shouldn't generally be modified directly, therefore this function is used to
     241                 :            :  * prepare a new copy, which the caller then modifies and then commits by
     242                 :            :  * calling commit_creds().
     243                 :            :  *
     244                 :            :  * Preparation involves making a copy of the objective creds for modification.
     245                 :            :  *
     246                 :            :  * Returns a pointer to the new creds-to-be if successful, NULL otherwise.
     247                 :            :  *
     248                 :            :  * Call commit_creds() or abort_creds() to clean up.
     249                 :            :  */
     250                 :     157692 : struct cred *prepare_creds(void)
     251                 :            : {
     252                 :     157692 :         struct task_struct *task = current;
     253                 :     157692 :         const struct cred *old;
     254                 :     157692 :         struct cred *new;
     255                 :            : 
     256                 :     157692 :         validate_process_creds();
     257                 :            : 
     258                 :     157692 :         new = kmem_cache_alloc(cred_jar, GFP_KERNEL);
     259         [ +  - ]:     157692 :         if (!new)
     260                 :            :                 return NULL;
     261                 :            : 
     262                 :     157692 :         kdebug("prepare_creds() alloc %p", new);
     263                 :            : 
     264                 :     157692 :         old = task->cred;
     265                 :     157692 :         memcpy(new, old, sizeof(struct cred));
     266                 :            : 
     267                 :     157692 :         new->non_rcu = 0;
     268                 :     157692 :         atomic_set(&new->usage, 1);
     269                 :     157692 :         set_cred_subscribers(new, 0);
     270                 :     157692 :         get_group_info(new->group_info);
     271                 :     157692 :         get_uid(new->user);
     272         [ +  + ]:     157692 :         get_user_ns(new->user_ns);
     273                 :            : 
     274                 :            : #ifdef CONFIG_KEYS
     275         [ +  + ]:     157692 :         key_get(new->session_keyring);
     276         [ -  + ]:     157692 :         key_get(new->process_keyring);
     277         [ -  + ]:     157692 :         key_get(new->thread_keyring);
     278         [ -  + ]:     157692 :         key_get(new->request_key_auth);
     279                 :            : #endif
     280                 :            : 
     281                 :            : #ifdef CONFIG_SECURITY
     282                 :     157692 :         new->security = NULL;
     283                 :            : #endif
     284                 :            : 
     285         [ -  + ]:     157692 :         if (security_prepare_creds(new, old, GFP_KERNEL_ACCOUNT) < 0)
     286                 :          0 :                 goto error;
     287                 :            :         validate_creds(new);
     288                 :            :         return new;
     289                 :            : 
     290                 :            : error:
     291                 :          0 :         abort_creds(new);
     292                 :          0 :         return NULL;
     293                 :            : }
     294                 :            : EXPORT_SYMBOL(prepare_creds);
     295                 :            : 
     296                 :            : /*
     297                 :            :  * Prepare credentials for current to perform an execve()
     298                 :            :  * - The caller must hold ->cred_guard_mutex
     299                 :            :  */
     300                 :      37290 : struct cred *prepare_exec_creds(void)
     301                 :            : {
     302                 :      37290 :         struct cred *new;
     303                 :            : 
     304                 :      37290 :         new = prepare_creds();
     305         [ +  - ]:      37290 :         if (!new)
     306                 :            :                 return new;
     307                 :            : 
     308                 :            : #ifdef CONFIG_KEYS
     309                 :            :         /* newly exec'd tasks don't get a thread keyring */
     310                 :      37290 :         key_put(new->thread_keyring);
     311                 :      37290 :         new->thread_keyring = NULL;
     312                 :            : 
     313                 :            :         /* inherit the session keyring; new process keyring */
     314                 :      37290 :         key_put(new->process_keyring);
     315                 :      37290 :         new->process_keyring = NULL;
     316                 :            : #endif
     317                 :            : 
     318                 :      37290 :         return new;
     319                 :            : }
     320                 :            : 
     321                 :            : /*
     322                 :            :  * Copy credentials for the new process created by fork()
     323                 :            :  *
     324                 :            :  * We share if we can, but under some circumstances we have to generate a new
     325                 :            :  * set.
     326                 :            :  *
     327                 :            :  * The new process gets the current process's subjective credentials as its
     328                 :            :  * objective and subjective credentials
     329                 :            :  */
     330                 :      15573 : int copy_creds(struct task_struct *p, unsigned long clone_flags)
     331                 :            : {
     332                 :      15573 :         struct cred *new;
     333                 :      15573 :         int ret;
     334                 :            : 
     335                 :            : #ifdef CONFIG_KEYS_REQUEST_CACHE
     336                 :            :         p->cached_requested_key = NULL;
     337                 :            : #endif
     338                 :            : 
     339                 :      15573 :         if (
     340                 :            : #ifdef CONFIG_KEYS
     341         [ +  - ]:      15573 :                 !p->cred->thread_keyring &&
     342                 :            : #endif
     343         [ +  + ]:      15573 :                 clone_flags & CLONE_THREAD
     344                 :            :             ) {
     345         [ +  - ]:        120 :                 p->real_cred = get_cred(p->cred);
     346         [ +  - ]:        120 :                 get_cred(p->cred);
     347                 :        120 :                 alter_cred_subscribers(p->cred, 2);
     348                 :        120 :                 kdebug("share_creds(%p{%d,%d})",
     349                 :            :                        p->cred, atomic_read(&p->cred->usage),
     350                 :            :                        read_cred_subscribers(p->cred));
     351                 :        120 :                 atomic_inc(&p->cred->user->processes);
     352                 :        120 :                 return 0;
     353                 :            :         }
     354                 :            : 
     355                 :      15453 :         new = prepare_creds();
     356         [ +  - ]:      15453 :         if (!new)
     357                 :            :                 return -ENOMEM;
     358                 :            : 
     359         [ -  + ]:      15453 :         if (clone_flags & CLONE_NEWUSER) {
     360                 :          0 :                 ret = create_user_ns(new);
     361                 :          0 :                 if (ret < 0)
     362                 :          0 :                         goto error_put;
     363                 :            :         }
     364                 :            : 
     365                 :            : #ifdef CONFIG_KEYS
     366                 :            :         /* new threads get their own thread keyrings if their parent already
     367                 :            :          * had one */
     368         [ -  + ]:      15453 :         if (new->thread_keyring) {
     369                 :          0 :                 key_put(new->thread_keyring);
     370                 :          0 :                 new->thread_keyring = NULL;
     371         [ #  # ]:          0 :                 if (clone_flags & CLONE_THREAD)
     372                 :          0 :                         install_thread_keyring_to_cred(new);
     373                 :            :         }
     374                 :            : 
     375                 :            :         /* The process keyring is only shared between the threads in a process;
     376                 :            :          * anything outside of those threads doesn't inherit.
     377                 :            :          */
     378         [ +  - ]:      15453 :         if (!(clone_flags & CLONE_THREAD)) {
     379                 :      15453 :                 key_put(new->process_keyring);
     380                 :      15453 :                 new->process_keyring = NULL;
     381                 :            :         }
     382                 :            : #endif
     383                 :            : 
     384                 :      15453 :         atomic_inc(&new->user->processes);
     385                 :      15453 :         p->cred = p->real_cred = get_cred(new);
     386                 :      15453 :         alter_cred_subscribers(new, 2);
     387                 :      15453 :         validate_creds(new);
     388                 :      15453 :         return 0;
     389                 :            : 
     390                 :            : error_put:
     391                 :          0 :         put_cred(new);
     392                 :          0 :         return ret;
     393                 :            : }
     394                 :            : 
     395                 :            : static bool cred_cap_issubset(const struct cred *set, const struct cred *subset)
     396                 :            : {
     397                 :            :         const struct user_namespace *set_ns = set->user_ns;
     398                 :            :         const struct user_namespace *subset_ns = subset->user_ns;
     399                 :            : 
     400                 :            :         /* If the two credentials are in the same user namespace see if
     401                 :            :          * the capabilities of subset are a subset of set.
     402                 :            :          */
     403                 :            :         if (set_ns == subset_ns)
     404                 :            :                 return cap_issubset(subset->cap_permitted, set->cap_permitted);
     405                 :            : 
     406                 :            :         /* The credentials are in a different user namespaces
     407                 :            :          * therefore one is a subset of the other only if a set is an
     408                 :            :          * ancestor of subset and set->euid is owner of subset or one
     409                 :            :          * of subsets ancestors.
     410                 :            :          */
     411                 :            :         for (;subset_ns != &init_user_ns; subset_ns = subset_ns->parent) {
     412                 :            :                 if ((set_ns == subset_ns->parent)  &&
     413                 :            :                     uid_eq(subset_ns->owner, set->euid))
     414                 :            :                         return true;
     415                 :            :         }
     416                 :            : 
     417                 :            :         return false;
     418                 :            : }
     419                 :            : 
     420                 :            : /**
     421                 :            :  * commit_creds - Install new credentials upon the current task
     422                 :            :  * @new: The credentials to be assigned
     423                 :            :  *
     424                 :            :  * Install a new set of credentials to the current task, using RCU to replace
     425                 :            :  * the old set.  Both the objective and the subjective credentials pointers are
     426                 :            :  * updated.  This function may not be called if the subjective credentials are
     427                 :            :  * in an overridden state.
     428                 :            :  *
     429                 :            :  * This function eats the caller's reference to the new credentials.
     430                 :            :  *
     431                 :            :  * Always returns 0 thus allowing this function to be tail-called at the end
     432                 :            :  * of, say, sys_setgid().
     433                 :            :  */
     434                 :      16476 : int commit_creds(struct cred *new)
     435                 :            : {
     436         [ -  + ]:      16476 :         struct task_struct *task = current;
     437                 :      16476 :         const struct cred *old = task->real_cred;
     438                 :            : 
     439                 :      16476 :         kdebug("commit_creds(%p{%d,%d})", new,
     440                 :            :                atomic_read(&new->usage),
     441                 :            :                read_cred_subscribers(new));
     442                 :            : 
     443         [ -  + ]:      16476 :         BUG_ON(task->cred != old);
     444                 :            : #ifdef CONFIG_DEBUG_CREDENTIALS
     445                 :            :         BUG_ON(read_cred_subscribers(old) < 2);
     446                 :            :         validate_creds(old);
     447                 :            :         validate_creds(new);
     448                 :            : #endif
     449         [ -  + ]:      16476 :         BUG_ON(atomic_read(&new->usage) < 1);
     450                 :            : 
     451         [ +  - ]:      16476 :         get_cred(new); /* we will require a ref for the subj creds too */
     452                 :            : 
     453                 :            :         /* dumpability changes */
     454   [ +  +  +  + ]:      16476 :         if (!uid_eq(old->euid, new->euid) ||
     455         [ +  - ]:      16296 :             !gid_eq(old->egid, new->egid) ||
     456         [ +  - ]:      16296 :             !uid_eq(old->fsuid, new->fsuid) ||
     457         [ -  + ]:      16296 :             !gid_eq(old->fsgid, new->fsgid) ||
     458                 :      16296 :             !cred_cap_issubset(old, new)) {
     459         [ +  - ]:        180 :                 if (task->mm)
     460                 :        180 :                         set_dumpable(task->mm, suid_dumpable);
     461                 :        180 :                 task->pdeath_signal = 0;
     462                 :            :                 /*
     463                 :            :                  * If a task drops privileges and becomes nondumpable,
     464                 :            :                  * the dumpability change must become visible before
     465                 :            :                  * the credential change; otherwise, a __ptrace_may_access()
     466                 :            :                  * racing with this change may be able to attach to a task it
     467                 :            :                  * shouldn't be able to attach to (as if the task had dropped
     468                 :            :                  * privileges without becoming nondumpable).
     469                 :            :                  * Pairs with a read barrier in __ptrace_may_access().
     470                 :            :                  */
     471                 :        180 :                 smp_wmb();
     472                 :            :         }
     473                 :            : 
     474                 :            :         /* alter the thread keyring */
     475         [ +  + ]:      16476 :         if (!uid_eq(new->fsuid, old->fsuid))
     476                 :         90 :                 key_fsuid_changed(new);
     477         [ +  + ]:      16476 :         if (!gid_eq(new->fsgid, old->fsgid))
     478                 :         90 :                 key_fsgid_changed(new);
     479                 :            : 
     480                 :            :         /* do it
     481                 :            :          * RLIMIT_NPROC limits on user->processes have already been checked
     482                 :            :          * in set_user().
     483                 :            :          */
     484                 :      16476 :         alter_cred_subscribers(new, 2);
     485         [ +  + ]:      16476 :         if (new->user != old->user)
     486                 :         90 :                 atomic_inc(&new->user->processes);
     487                 :      16476 :         rcu_assign_pointer(task->real_cred, new);
     488         [ +  + ]:      16476 :         rcu_assign_pointer(task->cred, new);
     489         [ +  + ]:      16476 :         if (new->user != old->user)
     490                 :         90 :                 atomic_dec(&old->user->processes);
     491                 :      16476 :         alter_cred_subscribers(old, -2);
     492                 :            : 
     493                 :            :         /* send notifications */
     494   [ +  +  +  + ]:      16476 :         if (!uid_eq(new->uid,   old->uid)  ||
     495         [ +  - ]:      16326 :             !uid_eq(new->euid,  old->euid) ||
     496         [ -  + ]:      16326 :             !uid_eq(new->suid,  old->suid) ||
     497                 :            :             !uid_eq(new->fsuid, old->fsuid))
     498                 :        150 :                 proc_id_connector(task, PROC_EVENT_UID);
     499                 :            : 
     500   [ +  +  +  + ]:      16476 :         if (!gid_eq(new->gid,   old->gid)  ||
     501         [ +  - ]:      16326 :             !gid_eq(new->egid,  old->egid) ||
     502         [ -  + ]:      16326 :             !gid_eq(new->sgid,  old->sgid) ||
     503                 :            :             !gid_eq(new->fsgid, old->fsgid))
     504                 :        150 :                 proc_id_connector(task, PROC_EVENT_GID);
     505                 :            : 
     506                 :            :         /* release the old obj and subj refs both */
     507                 :      16476 :         put_cred(old);
     508                 :      16476 :         put_cred(old);
     509                 :      16476 :         return 0;
     510                 :            : }
     511                 :            : EXPORT_SYMBOL(commit_creds);
     512                 :            : 
     513                 :            : /**
     514                 :            :  * abort_creds - Discard a set of credentials and unlock the current task
     515                 :            :  * @new: The credentials that were going to be applied
     516                 :            :  *
     517                 :            :  * Discard a set of credentials that were under construction and unlock the
     518                 :            :  * current task.
     519                 :            :  */
     520                 :      25080 : void abort_creds(struct cred *new)
     521                 :            : {
     522                 :      25080 :         kdebug("abort_creds(%p{%d,%d})", new,
     523                 :            :                atomic_read(&new->usage),
     524                 :            :                read_cred_subscribers(new));
     525                 :            : 
     526                 :            : #ifdef CONFIG_DEBUG_CREDENTIALS
     527                 :            :         BUG_ON(read_cred_subscribers(new) != 0);
     528                 :            : #endif
     529         [ -  + ]:      25080 :         BUG_ON(atomic_read(&new->usage) < 1);
     530                 :      25080 :         put_cred(new);
     531                 :      25080 : }
     532                 :            : EXPORT_SYMBOL(abort_creds);
     533                 :            : 
     534                 :            : /**
     535                 :            :  * override_creds - Override the current process's subjective credentials
     536                 :            :  * @new: The credentials to be assigned
     537                 :            :  *
     538                 :            :  * Install a set of temporary override subjective credentials on the current
     539                 :            :  * process, returning the old set for later reversion.
     540                 :            :  */
     541                 :     101583 : const struct cred *override_creds(const struct cred *new)
     542                 :            : {
     543                 :     101583 :         const struct cred *old = current->cred;
     544                 :            : 
     545                 :     101583 :         kdebug("override_creds(%p{%d,%d})", new,
     546                 :            :                atomic_read(&new->usage),
     547                 :            :                read_cred_subscribers(new));
     548                 :            : 
     549                 :     101583 :         validate_creds(old);
     550                 :     101583 :         validate_creds(new);
     551                 :            : 
     552                 :            :         /*
     553                 :            :          * NOTE! This uses 'get_new_cred()' rather than 'get_cred()'.
     554                 :            :          *
     555                 :            :          * That means that we do not clear the 'non_rcu' flag, since
     556                 :            :          * we are only installing the cred into the thread-synchronous
     557                 :            :          * '->cred' pointer, not the '->real_cred' pointer that is
     558                 :            :          * visible to other threads under RCU.
     559                 :            :          *
     560                 :            :          * Also note that we did validate_creds() manually, not depending
     561                 :            :          * on the validation in 'get_cred()'.
     562                 :            :          */
     563                 :     101583 :         get_new_cred((struct cred *)new);
     564                 :     101583 :         alter_cred_subscribers(new, 1);
     565                 :     101583 :         rcu_assign_pointer(current->cred, new);
     566                 :     101583 :         alter_cred_subscribers(old, -1);
     567                 :            : 
     568                 :     101583 :         kdebug("override_creds() = %p{%d,%d}", old,
     569                 :            :                atomic_read(&old->usage),
     570                 :            :                read_cred_subscribers(old));
     571                 :     101583 :         return old;
     572                 :            : }
     573                 :            : EXPORT_SYMBOL(override_creds);
     574                 :            : 
     575                 :            : /**
     576                 :            :  * revert_creds - Revert a temporary subjective credentials override
     577                 :            :  * @old: The credentials to be restored
     578                 :            :  *
     579                 :            :  * Revert a temporary set of override subjective credentials to an old set,
     580                 :            :  * discarding the override set.
     581                 :            :  */
     582                 :     101583 : void revert_creds(const struct cred *old)
     583                 :            : {
     584                 :     101583 :         const struct cred *override = current->cred;
     585                 :            : 
     586                 :     101583 :         kdebug("revert_creds(%p{%d,%d})", old,
     587                 :            :                atomic_read(&old->usage),
     588                 :            :                read_cred_subscribers(old));
     589                 :            : 
     590                 :     101583 :         validate_creds(old);
     591                 :     101583 :         validate_creds(override);
     592                 :     101583 :         alter_cred_subscribers(old, 1);
     593                 :     101583 :         rcu_assign_pointer(current->cred, old);
     594                 :     101583 :         alter_cred_subscribers(override, -1);
     595                 :     101583 :         put_cred(override);
     596                 :     101583 : }
     597                 :            : EXPORT_SYMBOL(revert_creds);
     598                 :            : 
     599                 :            : /**
     600                 :            :  * cred_fscmp - Compare two credentials with respect to filesystem access.
     601                 :            :  * @a: The first credential
     602                 :            :  * @b: The second credential
     603                 :            :  *
     604                 :            :  * cred_cmp() will return zero if both credentials have the same
     605                 :            :  * fsuid, fsgid, and supplementary groups.  That is, if they will both
     606                 :            :  * provide the same access to files based on mode/uid/gid.
     607                 :            :  * If the credentials are different, then either -1 or 1 will
     608                 :            :  * be returned depending on whether @a comes before or after @b
     609                 :            :  * respectively in an arbitrary, but stable, ordering of credentials.
     610                 :            :  *
     611                 :            :  * Return: -1, 0, or 1 depending on comparison
     612                 :            :  */
     613                 :          0 : int cred_fscmp(const struct cred *a, const struct cred *b)
     614                 :            : {
     615                 :          0 :         struct group_info *ga, *gb;
     616                 :          0 :         int g;
     617                 :            : 
     618         [ #  # ]:          0 :         if (a == b)
     619                 :            :                 return 0;
     620         [ #  # ]:          0 :         if (uid_lt(a->fsuid, b->fsuid))
     621                 :            :                 return -1;
     622         [ #  # ]:          0 :         if (uid_gt(a->fsuid, b->fsuid))
     623                 :            :                 return 1;
     624                 :            : 
     625         [ #  # ]:          0 :         if (gid_lt(a->fsgid, b->fsgid))
     626                 :            :                 return -1;
     627         [ #  # ]:          0 :         if (gid_gt(a->fsgid, b->fsgid))
     628                 :            :                 return 1;
     629                 :            : 
     630                 :          0 :         ga = a->group_info;
     631                 :          0 :         gb = b->group_info;
     632         [ #  # ]:          0 :         if (ga == gb)
     633                 :            :                 return 0;
     634         [ #  # ]:          0 :         if (ga == NULL)
     635                 :            :                 return -1;
     636         [ #  # ]:          0 :         if (gb == NULL)
     637                 :            :                 return 1;
     638         [ #  # ]:          0 :         if (ga->ngroups < gb->ngroups)
     639                 :            :                 return -1;
     640         [ #  # ]:          0 :         if (ga->ngroups > gb->ngroups)
     641                 :            :                 return 1;
     642                 :            : 
     643         [ #  # ]:          0 :         for (g = 0; g < ga->ngroups; g++) {
     644         [ #  # ]:          0 :                 if (gid_lt(ga->gid[g], gb->gid[g]))
     645                 :            :                         return -1;
     646         [ #  # ]:          0 :                 if (gid_gt(ga->gid[g], gb->gid[g]))
     647                 :            :                         return 1;
     648                 :            :         }
     649                 :            :         return 0;
     650                 :            : }
     651                 :            : EXPORT_SYMBOL(cred_fscmp);
     652                 :            : 
     653                 :            : /*
     654                 :            :  * initialise the credentials stuff
     655                 :            :  */
     656                 :         30 : void __init cred_init(void)
     657                 :            : {
     658                 :            :         /* allocate a slab in which we can store credentials */
     659                 :         30 :         cred_jar = kmem_cache_create("cred_jar", sizeof(struct cred), 0,
     660                 :            :                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT, NULL);
     661                 :         30 : }
     662                 :            : 
     663                 :            : /**
     664                 :            :  * prepare_kernel_cred - Prepare a set of credentials for a kernel service
     665                 :            :  * @daemon: A userspace daemon to be used as a reference
     666                 :            :  *
     667                 :            :  * Prepare a set of credentials for a kernel service.  This can then be used to
     668                 :            :  * override a task's own credentials so that work can be done on behalf of that
     669                 :            :  * task that requires a different subjective context.
     670                 :            :  *
     671                 :            :  * @daemon is used to provide a base for the security record, but can be NULL.
     672                 :            :  * If @daemon is supplied, then the security data will be derived from that;
     673                 :            :  * otherwise they'll be set to 0 and no groups, full capabilities and no keys.
     674                 :            :  *
     675                 :            :  * The caller may change these controls afterwards if desired.
     676                 :            :  *
     677                 :            :  * Returns the new credentials or NULL if out of memory.
     678                 :            :  *
     679                 :            :  * Does not take, and does not return holding current->cred_replace_mutex.
     680                 :            :  */
     681                 :        960 : struct cred *prepare_kernel_cred(struct task_struct *daemon)
     682                 :            : {
     683                 :        960 :         const struct cred *old;
     684                 :        960 :         struct cred *new;
     685                 :            : 
     686                 :        960 :         new = kmem_cache_alloc(cred_jar, GFP_KERNEL);
     687         [ +  - ]:        960 :         if (!new)
     688                 :            :                 return NULL;
     689                 :            : 
     690                 :        960 :         kdebug("prepare_kernel_cred() alloc %p", new);
     691                 :            : 
     692         [ +  + ]:        960 :         if (daemon)
     693                 :        900 :                 old = get_task_cred(daemon);
     694                 :            :         else
     695                 :         60 :                 old = get_cred(&init_cred);
     696                 :            : 
     697                 :        960 :         validate_creds(old);
     698                 :            : 
     699                 :        960 :         *new = *old;
     700                 :        960 :         new->non_rcu = 0;
     701                 :        960 :         atomic_set(&new->usage, 1);
     702                 :        960 :         set_cred_subscribers(new, 0);
     703                 :        960 :         get_uid(new->user);
     704                 :        960 :         get_user_ns(new->user_ns);
     705                 :        960 :         get_group_info(new->group_info);
     706                 :            : 
     707                 :            : #ifdef CONFIG_KEYS
     708                 :        960 :         new->session_keyring = NULL;
     709                 :        960 :         new->process_keyring = NULL;
     710                 :        960 :         new->thread_keyring = NULL;
     711                 :        960 :         new->request_key_auth = NULL;
     712                 :        960 :         new->jit_keyring = KEY_REQKEY_DEFL_THREAD_KEYRING;
     713                 :            : #endif
     714                 :            : 
     715                 :            : #ifdef CONFIG_SECURITY
     716                 :        960 :         new->security = NULL;
     717                 :            : #endif
     718         [ -  + ]:        960 :         if (security_prepare_creds(new, old, GFP_KERNEL_ACCOUNT) < 0)
     719                 :          0 :                 goto error;
     720                 :            : 
     721                 :        960 :         put_cred(old);
     722                 :        960 :         validate_creds(new);
     723                 :        960 :         return new;
     724                 :            : 
     725                 :            : error:
     726                 :          0 :         put_cred(new);
     727                 :          0 :         put_cred(old);
     728                 :          0 :         return NULL;
     729                 :            : }
     730                 :            : EXPORT_SYMBOL(prepare_kernel_cred);
     731                 :            : 
     732                 :            : /**
     733                 :            :  * set_security_override - Set the security ID in a set of credentials
     734                 :            :  * @new: The credentials to alter
     735                 :            :  * @secid: The LSM security ID to set
     736                 :            :  *
     737                 :            :  * Set the LSM security ID in a set of credentials so that the subjective
     738                 :            :  * security is overridden when an alternative set of credentials is used.
     739                 :            :  */
     740                 :          0 : int set_security_override(struct cred *new, u32 secid)
     741                 :            : {
     742                 :          0 :         return security_kernel_act_as(new, secid);
     743                 :            : }
     744                 :            : EXPORT_SYMBOL(set_security_override);
     745                 :            : 
     746                 :            : /**
     747                 :            :  * set_security_override_from_ctx - Set the security ID in a set of credentials
     748                 :            :  * @new: The credentials to alter
     749                 :            :  * @secctx: The LSM security context to generate the security ID from.
     750                 :            :  *
     751                 :            :  * Set the LSM security ID in a set of credentials so that the subjective
     752                 :            :  * security is overridden when an alternative set of credentials is used.  The
     753                 :            :  * security ID is specified in string form as a security context to be
     754                 :            :  * interpreted by the LSM.
     755                 :            :  */
     756                 :          0 : int set_security_override_from_ctx(struct cred *new, const char *secctx)
     757                 :            : {
     758                 :          0 :         u32 secid;
     759                 :          0 :         int ret;
     760                 :            : 
     761                 :          0 :         ret = security_secctx_to_secid(secctx, strlen(secctx), &secid);
     762         [ #  # ]:          0 :         if (ret < 0)
     763                 :            :                 return ret;
     764                 :            : 
     765                 :          0 :         return set_security_override(new, secid);
     766                 :            : }
     767                 :            : EXPORT_SYMBOL(set_security_override_from_ctx);
     768                 :            : 
     769                 :            : /**
     770                 :            :  * set_create_files_as - Set the LSM file create context in a set of credentials
     771                 :            :  * @new: The credentials to alter
     772                 :            :  * @inode: The inode to take the context from
     773                 :            :  *
     774                 :            :  * Change the LSM file creation context in a set of credentials to be the same
     775                 :            :  * as the object context of the specified inode, so that the new inodes have
     776                 :            :  * the same MAC context as that inode.
     777                 :            :  */
     778                 :          0 : int set_create_files_as(struct cred *new, struct inode *inode)
     779                 :            : {
     780   [ #  #  #  # ]:          0 :         if (!uid_valid(inode->i_uid) || !gid_valid(inode->i_gid))
     781                 :            :                 return -EINVAL;
     782                 :          0 :         new->fsuid = inode->i_uid;
     783                 :          0 :         new->fsgid = inode->i_gid;
     784                 :          0 :         return security_kernel_create_files_as(new, inode);
     785                 :            : }
     786                 :            : EXPORT_SYMBOL(set_create_files_as);
     787                 :            : 
     788                 :            : #ifdef CONFIG_DEBUG_CREDENTIALS
     789                 :            : 
     790                 :            : bool creds_are_invalid(const struct cred *cred)
     791                 :            : {
     792                 :            :         if (cred->magic != CRED_MAGIC)
     793                 :            :                 return true;
     794                 :            :         return false;
     795                 :            : }
     796                 :            : EXPORT_SYMBOL(creds_are_invalid);
     797                 :            : 
     798                 :            : /*
     799                 :            :  * dump invalid credentials
     800                 :            :  */
     801                 :            : static void dump_invalid_creds(const struct cred *cred, const char *label,
     802                 :            :                                const struct task_struct *tsk)
     803                 :            : {
     804                 :            :         printk(KERN_ERR "CRED: %s credentials: %p %s%s%s\n",
     805                 :            :                label, cred,
     806                 :            :                cred == &init_cred ? "[init]" : "",
     807                 :            :                cred == tsk->real_cred ? "[real]" : "",
     808                 :            :                cred == tsk->cred ? "[eff]" : "");
     809                 :            :         printk(KERN_ERR "CRED: ->magic=%x, put_addr=%p\n",
     810                 :            :                cred->magic, cred->put_addr);
     811                 :            :         printk(KERN_ERR "CRED: ->usage=%d, subscr=%d\n",
     812                 :            :                atomic_read(&cred->usage),
     813                 :            :                read_cred_subscribers(cred));
     814                 :            :         printk(KERN_ERR "CRED: ->*uid = { %d,%d,%d,%d }\n",
     815                 :            :                 from_kuid_munged(&init_user_ns, cred->uid),
     816                 :            :                 from_kuid_munged(&init_user_ns, cred->euid),
     817                 :            :                 from_kuid_munged(&init_user_ns, cred->suid),
     818                 :            :                 from_kuid_munged(&init_user_ns, cred->fsuid));
     819                 :            :         printk(KERN_ERR "CRED: ->*gid = { %d,%d,%d,%d }\n",
     820                 :            :                 from_kgid_munged(&init_user_ns, cred->gid),
     821                 :            :                 from_kgid_munged(&init_user_ns, cred->egid),
     822                 :            :                 from_kgid_munged(&init_user_ns, cred->sgid),
     823                 :            :                 from_kgid_munged(&init_user_ns, cred->fsgid));
     824                 :            : #ifdef CONFIG_SECURITY
     825                 :            :         printk(KERN_ERR "CRED: ->security is %p\n", cred->security);
     826                 :            :         if ((unsigned long) cred->security >= PAGE_SIZE &&
     827                 :            :             (((unsigned long) cred->security & 0xffffff00) !=
     828                 :            :              (POISON_FREE << 24 | POISON_FREE << 16 | POISON_FREE << 8)))
     829                 :            :                 printk(KERN_ERR "CRED: ->security {%x, %x}\n",
     830                 :            :                        ((u32*)cred->security)[0],
     831                 :            :                        ((u32*)cred->security)[1]);
     832                 :            : #endif
     833                 :            : }
     834                 :            : 
     835                 :            : /*
     836                 :            :  * report use of invalid credentials
     837                 :            :  */
     838                 :            : void __invalid_creds(const struct cred *cred, const char *file, unsigned line)
     839                 :            : {
     840                 :            :         printk(KERN_ERR "CRED: Invalid credentials\n");
     841                 :            :         printk(KERN_ERR "CRED: At %s:%u\n", file, line);
     842                 :            :         dump_invalid_creds(cred, "Specified", current);
     843                 :            :         BUG();
     844                 :            : }
     845                 :            : EXPORT_SYMBOL(__invalid_creds);
     846                 :            : 
     847                 :            : /*
     848                 :            :  * check the credentials on a process
     849                 :            :  */
     850                 :            : void __validate_process_creds(struct task_struct *tsk,
     851                 :            :                               const char *file, unsigned line)
     852                 :            : {
     853                 :            :         if (tsk->cred == tsk->real_cred) {
     854                 :            :                 if (unlikely(read_cred_subscribers(tsk->cred) < 2 ||
     855                 :            :                              creds_are_invalid(tsk->cred)))
     856                 :            :                         goto invalid_creds;
     857                 :            :         } else {
     858                 :            :                 if (unlikely(read_cred_subscribers(tsk->real_cred) < 1 ||
     859                 :            :                              read_cred_subscribers(tsk->cred) < 1 ||
     860                 :            :                              creds_are_invalid(tsk->real_cred) ||
     861                 :            :                              creds_are_invalid(tsk->cred)))
     862                 :            :                         goto invalid_creds;
     863                 :            :         }
     864                 :            :         return;
     865                 :            : 
     866                 :            : invalid_creds:
     867                 :            :         printk(KERN_ERR "CRED: Invalid process credentials\n");
     868                 :            :         printk(KERN_ERR "CRED: At %s:%u\n", file, line);
     869                 :            : 
     870                 :            :         dump_invalid_creds(tsk->real_cred, "Real", tsk);
     871                 :            :         if (tsk->cred != tsk->real_cred)
     872                 :            :                 dump_invalid_creds(tsk->cred, "Effective", tsk);
     873                 :            :         else
     874                 :            :                 printk(KERN_ERR "CRED: Effective creds == Real creds\n");
     875                 :            :         BUG();
     876                 :            : }
     877                 :            : EXPORT_SYMBOL(__validate_process_creds);
     878                 :            : 
     879                 :            : /*
     880                 :            :  * check creds for do_exit()
     881                 :            :  */
     882                 :            : void validate_creds_for_do_exit(struct task_struct *tsk)
     883                 :            : {
     884                 :            :         kdebug("validate_creds_for_do_exit(%p,%p{%d,%d})",
     885                 :            :                tsk->real_cred, tsk->cred,
     886                 :            :                atomic_read(&tsk->cred->usage),
     887                 :            :                read_cred_subscribers(tsk->cred));
     888                 :            : 
     889                 :            :         __validate_process_creds(tsk, __FILE__, __LINE__);
     890                 :            : }
     891                 :            : 
     892                 :            : #endif /* CONFIG_DEBUG_CREDENTIALS */

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