security/apparmor/file.c

   1 /*
   2  * AppArmor security module
   3  *
   4  * This file contains AppArmor mediation of files
   5  *
   6  * Copyright (C) 1998-2008 Novell/SUSE
   7  * Copyright 2009-2010 Canonical Ltd.
   8  *
   9  * This program is free software; you can redistribute it and/or
  10  * modify it under the terms of the GNU General Public License as
  11  * published by the Free Software Foundation, version 2 of the
  12  * License.
  13  */
  14
  15 #include <linux/tty.h>
  16 #include <linux/fdtable.h>
  17 #include <linux/file.h>
  18
  19 #include "include/apparmor.h"
  20 #include "include/audit.h"
  21 #include "include/context.h"
  22 #include "include/file.h"
  23 #include "include/match.h"
  24 #include "include/path.h"
  25 #include "include/policy.h"
  26 #include "include/label.h"
  27
  28 static u32 map_mask_to_chr_mask(u32 mask)
  29 {
  30         u32 m = mask & PERMS_CHRS_MASK;
  31
  32         if (mask & AA_MAY_GETATTR)
  33                 m |= MAY_READ;
  34         if (mask & (AA_MAY_SETATTR | AA_MAY_CHMOD | AA_MAY_CHOWN))
  35                 m |= MAY_WRITE;
  36
  37         return m;
  38 }
  39
  40 /**
  41  * audit_file_mask - convert mask to permission string
  42  * @buffer: buffer to write string to (NOT NULL)
  43  * @mask: permission mask to convert
  44  */
  45 static void audit_file_mask(struct audit_buffer *ab, u32 mask)
  46 {
  47         char str[10];
  48
  49         aa_perm_mask_to_str(str, aa_file_perm_chrs, map_mask_to_chr_mask(mask));
  50         audit_log_string(ab, str);
  51 }
  52
  53 /**
  54  * file_audit_cb - call back for file specific audit fields
  55  * @ab: audit_buffer  (NOT NULL)
  56  * @va: audit struct to audit values of  (NOT NULL)
  57  */
  58 static void file_audit_cb(struct audit_buffer *ab, void *va)
  59 {
  60         struct common_audit_data *sa = va;
  61         kuid_t fsuid = current_fsuid();
  62
  63         if (aad(sa)->request & AA_AUDIT_FILE_MASK) {
  64                 audit_log_format(ab, " requested_mask=");
  65                 audit_file_mask(ab, aad(sa)->request);
  66         }
  67         if (aad(sa)->denied & AA_AUDIT_FILE_MASK) {
  68                 audit_log_format(ab, " denied_mask=");
  69                 audit_file_mask(ab, aad(sa)->denied);
  70         }
  71         if (aad(sa)->request & AA_AUDIT_FILE_MASK) {
  72                 audit_log_format(ab, " fsuid=%d",
  73                                  from_kuid(&init_user_ns, fsuid));
  74                 audit_log_format(ab, " ouid=%d",
  75                                  from_kuid(&init_user_ns, aad(sa)->fs.ouid));
  76         }
  77
  78         if (aad(sa)->peer) {
  79                 audit_log_format(ab, " target=");
  80                 aa_label_xaudit(ab, labels_ns(aad(sa)->label), aad(sa)->peer,
  81                                 FLAG_VIEW_SUBNS, GFP_ATOMIC);
  82         } else if (aad(sa)->fs.target) {
  83                 audit_log_format(ab, " target=");
  84                 audit_log_untrustedstring(ab, aad(sa)->fs.target);
  85         }
  86 }
  87
  88 /**
  89  * aa_audit_file - handle the auditing of file operations
  90  * @profile: the profile being enforced  (NOT NULL)
  91  * @perms: the permissions computed for the request (NOT NULL)
  92  * @op: operation being mediated
  93  * @request: permissions requested
  94  * @name: name of object being mediated (MAYBE NULL)
  95  * @target: name of target (MAYBE NULL)
  96  * @tlabel: target label (MAY BE NULL)
  97  * @ouid: object uid
  98  * @info: extra information message (MAYBE NULL)
  99  * @error: 0 if operation allowed else failure error code
 100  *
 101  * Returns: %0 or error on failure
 102  */
 103 int aa_audit_file(struct aa_profile *profile, struct aa_perms *perms,
 104                   const char *op, u32 request, const char *name,
 105                   const char *target, struct aa_label *tlabel,
 106                   kuid_t ouid, const char *info, int error)
 107 {
 108         int type = AUDIT_APPARMOR_AUTO;
 109         DEFINE_AUDIT_DATA(sa, LSM_AUDIT_DATA_TASK, op);
 110
 111         sa.u.tsk = NULL;
 112         aad(&sa)->request = request;
 113         aad(&sa)->name = name;
 114         aad(&sa)->fs.target = target;
 115         aad(&sa)->peer = tlabel;
 116         aad(&sa)->fs.ouid = ouid;
 117         aad(&sa)->info = info;
 118         aad(&sa)->error = error;
 119         sa.u.tsk = NULL;
 120
 121         if (likely(!aad(&sa)->error)) {
 122                 u32 mask = perms->audit;
 123
 124                 if (unlikely(AUDIT_MODE(profile) == AUDIT_ALL))
 125                         mask = 0xffff;
 126
 127                 /* mask off perms that are not being force audited */
 128                 aad(&sa)->request &= mask;
 129
 130                 if (likely(!aad(&sa)->request))
 131                         return 0;
 132                 type = AUDIT_APPARMOR_AUDIT;
 133         } else {
 134                 /* only report permissions that were denied */
 135                 aad(&sa)->request = aad(&sa)->request & ~perms->allow;
 136                 AA_BUG(!aad(&sa)->request);
 137
 138                 if (aad(&sa)->request & perms->kill)
 139                         type = AUDIT_APPARMOR_KILL;
 140
 141                 /* quiet known rejects, assumes quiet and kill do not overlap */
 142                 if ((aad(&sa)->request & perms->quiet) &&
 143                     AUDIT_MODE(profile) != AUDIT_NOQUIET &&
 144                     AUDIT_MODE(profile) != AUDIT_ALL)
 145                         aad(&sa)->request &= ~perms->quiet;
 146
 147                 if (!aad(&sa)->request)
 148                         return aad(&sa)->error;
 149         }
 150
 151         aad(&sa)->denied = aad(&sa)->request & ~perms->allow;
 152         return aa_audit(type, profile, &sa, file_audit_cb);
 153 }
 154
 155 /**
 156  * is_deleted - test if a file has been completely unlinked
 157  * @dentry: dentry of file to test for deletion  (NOT NULL)
 158  *
 159  * Returns: %1 if deleted else %0
 160  */
 161 static inline bool is_deleted(struct dentry *dentry)
 162 {
 163         if (d_unlinked(dentry) && d_backing_inode(dentry)->i_nlink == 0)
 164                 return 1;
 165         return 0;
 166 }
 167
 168 static int path_name(const char *op, struct aa_label *label,
 169                      const struct path *path, int flags, char *buffer,
 170                      const char **name, struct path_cond *cond, u32 request)
 171 {
 172         struct aa_profile *profile;
 173         const char *info = NULL;
 174         int error;
 175
 176         error = aa_path_name(path, flags, buffer, name, &info,
 177                              labels_profile(label)->disconnected);
 178         if (error) {
 179                 fn_for_each_confined(label, profile,
 180                         aa_audit_file(profile, &nullperms, op, request, *name,
 181                                       NULL, NULL, cond->uid, info, error));
 182                 return error;
 183         }
 184
 185         return 0;
 186 }
 187
 188 /**
 189  * map_old_perms - map old file perms layout to the new layout
 190  * @old: permission set in old mapping
 191  *
 192  * Returns: new permission mapping
 193  */
 194 static u32 map_old_perms(u32 old)
 195 {
 196         u32 new = old & 0xf;
 197         if (old & MAY_READ)
 198                 new |= AA_MAY_GETATTR | AA_MAY_OPEN;
 199         if (old & MAY_WRITE)
 200                 new |= AA_MAY_SETATTR | AA_MAY_CREATE | AA_MAY_DELETE |
 201                        AA_MAY_CHMOD | AA_MAY_CHOWN | AA_MAY_OPEN;
 202         if (old & 0x10)
 203                 new |= AA_MAY_LINK;
 204         /* the old mapping lock and link_subset flags where overlaid
 205          * and use was determined by part of a pair that they were in
 206          */
 207         if (old & 0x20)
 208                 new |= AA_MAY_LOCK | AA_LINK_SUBSET;
 209         if (old & 0x40) /* AA_EXEC_MMAP */
 210                 new |= AA_EXEC_MMAP;
 211
 212         return new;
 213 }
 214
 215 /**
 216  * aa_compute_fperms - convert dfa compressed perms to internal perms
 217  * @dfa: dfa to compute perms for   (NOT NULL)
 218  * @state: state in dfa
 219  * @cond:  conditions to consider  (NOT NULL)
 220  *
 221  * TODO: convert from dfa + state to permission entry, do computation conversion
 222  *       at load time.
 223  *
 224  * Returns: computed permission set
 225  */
 226 struct aa_perms aa_compute_fperms(struct aa_dfa *dfa, unsigned int state,
 227                                   struct path_cond *cond)
 228 {
 229         /* FIXME: change over to new dfa format
 230          * currently file perms are encoded in the dfa, new format
 231          * splits the permissions from the dfa.  This mapping can be
 232          * done at profile load
 233          */
 234         struct aa_perms perms = { };
 235
 236         if (uid_eq(current_fsuid(), cond->uid)) {
 237                 perms.allow = map_old_perms(dfa_user_allow(dfa, state));
 238                 perms.audit = map_old_perms(dfa_user_audit(dfa, state));
 239                 perms.quiet = map_old_perms(dfa_user_quiet(dfa, state));
 240                 perms.xindex = dfa_user_xindex(dfa, state);
 241         } else {
 242                 perms.allow = map_old_perms(dfa_other_allow(dfa, state));
 243                 perms.audit = map_old_perms(dfa_other_audit(dfa, state));
 244                 perms.quiet = map_old_perms(dfa_other_quiet(dfa, state));
 245                 perms.xindex = dfa_other_xindex(dfa, state);
 246         }
 247         perms.allow |= AA_MAY_GETATTR;
 248
 249         /* change_profile wasn't determined by ownership in old mapping */
 250         if (ACCEPT_TABLE(dfa)[state] & 0x80000000)
 251                 perms.allow |= AA_MAY_CHANGE_PROFILE;
 252         if (ACCEPT_TABLE(dfa)[state] & 0x40000000)
 253                 perms.allow |= AA_MAY_ONEXEC;
 254
 255         return perms;
 256 }
 257
 258 /**
 259  * aa_str_perms - find permission that match @name
 260  * @dfa: to match against  (MAYBE NULL)
 261  * @state: state to start matching in
 262  * @name: string to match against dfa  (NOT NULL)
 263  * @cond: conditions to consider for permission set computation  (NOT NULL)
 264  * @perms: Returns - the permissions found when matching @name
 265  *
 266  * Returns: the final state in @dfa when beginning @start and walking @name
 267  */
 268 unsigned int aa_str_perms(struct aa_dfa *dfa, unsigned int start,
 269                           const char *name, struct path_cond *cond,
 270                           struct aa_perms *perms)
 271 {
 272         unsigned int state;
 273         state = aa_dfa_match(dfa, start, name);
 274         *perms = aa_compute_fperms(dfa, state, cond);
 275
 276         return state;
 277 }
 278
 279 int __aa_path_perm(const char *op, struct aa_profile *profile, const char *name,
 280                    u32 request, struct path_cond *cond, int flags,
 281                    struct aa_perms *perms)
 282 {
 283         int e = 0;
 284
 285         if (profile_unconfined(profile))
 286                 return 0;
 287         aa_str_perms(profile->file.dfa, profile->file.start, name, cond, perms);
 288         if (request & ~perms->allow)
 289                 e = -EACCES;
 290         return aa_audit_file(profile, perms, op, request, name, NULL, NULL,
 291                              cond->uid, NULL, e);
 292 }
 293
 294
 295 static int profile_path_perm(const char *op, struct aa_profile *profile,
 296                              const struct path *path, char *buffer, u32 request,
 297                              struct path_cond *cond, int flags,
 298                              struct aa_perms *perms)
 299 {
 300         const char *name;
 301         int error;
 302
 303         if (profile_unconfined(profile))
 304                 return 0;
 305
 306         error = path_name(op, &profile->label, path,
 307                           flags | profile->path_flags, buffer, &name, cond,
 308                           request);
 309         if (error)
 310                 return error;
 311         return __aa_path_perm(op, profile, name, request, cond, flags,
 312                               perms);
 313 }
 314
 315 /**
 316  * aa_path_perm - do permissions check & audit for @path
 317  * @op: operation being checked
 318  * @label: profile being enforced  (NOT NULL)
 319  * @path: path to check permissions of  (NOT NULL)
 320  * @flags: any additional path flags beyond what the profile specifies
 321  * @request: requested permissions
 322  * @cond: conditional info for this request  (NOT NULL)
 323  *
 324  * Returns: %0 else error if access denied or other error
 325  */
 326 int aa_path_perm(const char *op, struct aa_label *label,
 327                  const struct path *path, int flags, u32 request,
 328                  struct path_cond *cond)
 329 {
 330         struct aa_perms perms = {};
 331         struct aa_profile *profile;
 332         char *buffer = NULL;
 333         int error;
 334
 335         flags |= PATH_DELEGATE_DELETED | (S_ISDIR(cond->mode) ? PATH_IS_DIR :
 336                                                                 0);
 337         get_buffers(buffer);
 338         error = fn_for_each_confined(label, profile,
 339                         profile_path_perm(op, profile, path, buffer, request,
 340                                           cond, flags, &perms));
 341
 342         put_buffers(buffer);
 343
 344         return error;
 345 }
 346
 347 /**
 348  * xindex_is_subset - helper for aa_path_link
 349  * @link: link permission set
 350  * @target: target permission set
 351  *
 352  * test target x permissions are equal OR a subset of link x permissions
 353  * this is done as part of the subset test, where a hardlink must have
 354  * a subset of permissions that the target has.
 355  *
 356  * Returns: %1 if subset else %0
 357  */
 358 static inline bool xindex_is_subset(u32 link, u32 target)
 359 {
 360         if (((link & ~AA_X_UNSAFE) != (target & ~AA_X_UNSAFE)) ||
 361             ((link & AA_X_UNSAFE) && !(target & AA_X_UNSAFE)))
 362                 return 0;
 363
 364         return 1;
 365 }
 366
 367 static int profile_path_link(struct aa_profile *profile,
 368                              const struct path *link, char *buffer,
 369                              const struct path *target, char *buffer2,
 370                              struct path_cond *cond)
 371 {
 372         const char *lname, *tname = NULL;
 373         struct aa_perms lperms = {}, perms;
 374         const char *info = NULL;
 375         u32 request = AA_MAY_LINK;
 376         unsigned int state;
 377         int error;
 378
 379         error = path_name(OP_LINK, &profile->label, link, profile->path_flags,
 380                           buffer, &lname, cond, AA_MAY_LINK);
 381         if (error)
 382                 goto audit;
 383
 384         /* buffer2 freed below, tname is pointer in buffer2 */
 385         error = path_name(OP_LINK, &profile->label, target, profile->path_flags,
 386                           buffer2, &tname, cond, AA_MAY_LINK);
 387         if (error)
 388                 goto audit;
 389
 390         error = -EACCES;
 391         /* aa_str_perms - handles the case of the dfa being NULL */
 392         state = aa_str_perms(profile->file.dfa, profile->file.start, lname,
 393                              cond, &lperms);
 394
 395         if (!(lperms.allow & AA_MAY_LINK))
 396                 goto audit;
 397
 398         /* test to see if target can be paired with link */
 399         state = aa_dfa_null_transition(profile->file.dfa, state);
 400         aa_str_perms(profile->file.dfa, state, tname, cond, &perms);
 401
 402         /* force audit/quiet masks for link are stored in the second entry
 403          * in the link pair.
 404          */
 405         lperms.audit = perms.audit;
 406         lperms.quiet = perms.quiet;
 407         lperms.kill = perms.kill;
 408
 409         if (!(perms.allow & AA_MAY_LINK)) {
 410                 info = "target restricted";
 411                 lperms = perms;
 412                 goto audit;
 413         }
 414
 415         /* done if link subset test is not required */
 416         if (!(perms.allow & AA_LINK_SUBSET))
 417                 goto done_tests;
 418
 419         /* Do link perm subset test requiring allowed permission on link are
 420          * a subset of the allowed permissions on target.
 421          */
 422         aa_str_perms(profile->file.dfa, profile->file.start, tname, cond,
 423                      &perms);
 424
 425         /* AA_MAY_LINK is not considered in the subset test */
 426         request = lperms.allow & ~AA_MAY_LINK;
 427         lperms.allow &= perms.allow | AA_MAY_LINK;
 428
 429         request |= AA_AUDIT_FILE_MASK & (lperms.allow & ~perms.allow);
 430         if (request & ~lperms.allow) {
 431                 goto audit;
 432         } else if ((lperms.allow & MAY_EXEC) &&
 433                    !xindex_is_subset(lperms.xindex, perms.xindex)) {
 434                 lperms.allow &= ~MAY_EXEC;
 435                 request |= MAY_EXEC;
 436                 info = "link not subset of target";
 437                 goto audit;
 438         }
 439
 440 done_tests:
 441         error = 0;
 442
 443 audit:
 444         return aa_audit_file(profile, &lperms, OP_LINK, request, lname, tname,
 445                              NULL, cond->uid, info, error);
 446 }
 447
 448 /**
 449  * aa_path_link - Handle hard link permission check
 450  * @label: the label being enforced  (NOT NULL)
 451  * @old_dentry: the target dentry  (NOT NULL)
 452  * @new_dir: directory the new link will be created in  (NOT NULL)
 453  * @new_dentry: the link being created  (NOT NULL)
 454  *
 455  * Handle the permission test for a link & target pair.  Permission
 456  * is encoded as a pair where the link permission is determined
 457  * first, and if allowed, the target is tested.  The target test
 458  * is done from the point of the link match (not start of DFA)
 459  * making the target permission dependent on the link permission match.
 460  *
 461  * The subset test if required forces that permissions granted
 462  * on link are a subset of the permission granted to target.
 463  *
 464  * Returns: %0 if allowed else error
 465  */
 466 int aa_path_link(struct aa_label *label, struct dentry *old_dentry,
 467                  const struct path *new_dir, struct dentry *new_dentry)
 468 {
 469         struct path link = { .mnt = new_dir->mnt, .dentry = new_dentry };
 470         struct path target = { .mnt = new_dir->mnt, .dentry = old_dentry };
 471         struct path_cond cond = {
 472                 d_backing_inode(old_dentry)->i_uid,
 473                 d_backing_inode(old_dentry)->i_mode
 474         };
 475         char *buffer = NULL, *buffer2 = NULL;
 476         struct aa_profile *profile;
 477         int error;
 478
 479         /* buffer freed below, lname is pointer in buffer */
 480         get_buffers(buffer, buffer2);
 481         error = fn_for_each_confined(label, profile,
 482                         profile_path_link(profile, &link, buffer, &target,
 483                                           buffer2, &cond));
 484         put_buffers(buffer, buffer2);
 485
 486         return error;
 487 }
 488
 489 static void update_file_ctx(struct aa_file_ctx *fctx, struct aa_label *label,
 490                             u32 request)
 491 {
 492         struct aa_label *l, *old;
 493
 494         /* update caching of label on file_ctx */
 495         spin_lock(&fctx->lock);
 496         old = rcu_dereference_protected(fctx->label,
 497                                         spin_is_locked(&fctx->lock));
 498         l = aa_label_merge(old, label, GFP_ATOMIC);
 499         if (l) {
 500                 if (l != old) {
 501                         rcu_assign_pointer(fctx->label, l);
 502                         aa_put_label(old);
 503                 } else
 504                         aa_put_label(l);
 505                 fctx->allow |= request;
 506         }
 507         spin_unlock(&fctx->lock);
 508 }
 509
 510 static int __file_path_perm(const char *op, struct aa_label *label,
 511                             struct aa_label *flabel, struct file *file,
 512                             u32 request, u32 denied)
 513 {
 514         struct aa_profile *profile;
 515         struct aa_perms perms = {};
 516         struct path_cond cond = {
 517                 .uid = file_inode(file)->i_uid,
 518                 .mode = file_inode(file)->i_mode
 519         };
 520         char *buffer;
 521         int flags, error;
 522
 523         /* revalidation due to label out of date. No revocation at this time */
 524         if (!denied && aa_label_is_subset(flabel, label))
 525                 /* TODO: check for revocation on stale profiles */
 526                 return 0;
 527
 528         flags = PATH_DELEGATE_DELETED | (S_ISDIR(cond.mode) ? PATH_IS_DIR : 0);
 529         get_buffers(buffer);
 530
 531         /* check every profile in task label not in current cache */
 532         error = fn_for_each_not_in_set(flabel, label, profile,
 533                         profile_path_perm(op, profile, &file->f_path, buffer,
 534                                           request, &cond, flags, &perms));
 535         if (denied && !error) {
 536                 /*
 537                  * check every profile in file label that was not tested
 538                  * in the initial check above.
 539                  *
 540                  * TODO: cache full perms so this only happens because of
 541                  * conditionals
 542                  * TODO: don't audit here
 543                  */
 544                 if (label == flabel)
 545                         error = fn_for_each(label, profile,
 546                                 profile_path_perm(op, profile, &file->f_path,
 547                                                   buffer, request, &cond, flags,
 548                                                   &perms));
 549                 else
 550                         error = fn_for_each_not_in_set(label, flabel, profile,
 551                                 profile_path_perm(op, profile, &file->f_path,
 552                                                   buffer, request, &cond, flags,
 553                                                   &perms));
 554         }
 555         if (!error)
 556                 update_file_ctx(file_ctx(file), label, request);
 557
 558         put_buffers(buffer);
 559
 560         return error;
 561 }
 562
 563 /**
 564  * aa_file_perm - do permission revalidation check & audit for @file
 565  * @op: operation being checked
 566  * @label: label being enforced   (NOT NULL)
 567  * @file: file to revalidate access permissions on  (NOT NULL)
 568  * @request: requested permissions
 569  *
 570  * Returns: %0 if access allowed else error
 571  */
 572 int aa_file_perm(const char *op, struct aa_label *label, struct file *file,
 573                  u32 request)
 574 {
 575         struct aa_file_ctx *fctx;
 576         struct aa_label *flabel;
 577         u32 denied;
 578         int error = 0;
 579
 580         AA_BUG(!label);
 581         AA_BUG(!file);
 582
 583         fctx = file_ctx(file);
 584
 585         rcu_read_lock();
 586         flabel  = rcu_dereference(fctx->label);
 587         AA_BUG(!flabel);
 588
 589         /* revalidate access, if task is unconfined, or the cached cred
 590          * doesn't match or if the request is for more permissions than
 591          * was granted.
 592          *
 593          * Note: the test for !unconfined(flabel) is to handle file
 594          *       delegation from unconfined tasks
 595          */
 596         denied = request & ~fctx->allow;
 597         if (unconfined(label) || unconfined(flabel) ||
 598             (!denied && aa_label_is_subset(flabel, label)))
 599                 goto done;
 600
 601         /* TODO: label cross check */
 602
 603         if (file->f_path.mnt && path_mediated_fs(file->f_path.dentry))
 604                 error = __file_path_perm(op, label, flabel, file, request,
 605                                          denied);
 606
 607 done:
 608         rcu_read_unlock();
 609
 610         return error;
 611 }
 612
 613 static void revalidate_tty(struct aa_label *label)
 614 {
 615         struct tty_struct *tty;
 616         int drop_tty = 0;
 617
 618         tty = get_current_tty();
 619         if (!tty)
 620                 return;
 621
 622         spin_lock(&tty->files_lock);
 623         if (!list_empty(&tty->tty_files)) {
 624                 struct tty_file_private *file_priv;
 625                 struct file *file;
 626                 /* TODO: Revalidate access to controlling tty. */
 627                 file_priv = list_first_entry(&tty->tty_files,
 628                                              struct tty_file_private, list);
 629                 file = file_priv->file;
 630
 631                 if (aa_file_perm(OP_INHERIT, label, file, MAY_READ | MAY_WRITE))
 632                         drop_tty = 1;
 633         }
 634         spin_unlock(&tty->files_lock);
 635         tty_kref_put(tty);
 636
 637         if (drop_tty)
 638                 no_tty();
 639 }
 640
 641 static int match_file(const void *p, struct file *file, unsigned int fd)
 642 {
 643         struct aa_label *label = (struct aa_label *)p;
 644
 645         if (aa_file_perm(OP_INHERIT, label, file, aa_map_file_to_perms(file)))
 646                 return fd + 1;
 647         return 0;
 648 }
 649
 650
 651 /* based on selinux's flush_unauthorized_files */
 652 void aa_inherit_files(const struct cred *cred, struct files_struct *files)
 653 {
 654         struct aa_label *label = aa_get_newest_cred_label(cred);
 655         struct file *devnull = NULL;
 656         unsigned int n;
 657
 658         revalidate_tty(label);
 659
 660         /* Revalidate access to inherited open files. */
 661         n = iterate_fd(files, 0, match_file, label);
 662         if (!n) /* none found? */
 663                 goto out;
 664
 665         devnull = dentry_open(&aa_null, O_RDWR, cred);
 666         if (IS_ERR(devnull))
 667                 devnull = NULL;
 668         /* replace all the matching ones with this */
 669         do {
 670                 replace_fd(n - 1, devnull, 0);
 671         } while ((n = iterate_fd(files, n, match_file, label)) != 0);
 672         if (devnull)
 673                 fput(devnull);
 674 out:
 675         aa_put_label(label);
 676 }