security/apparmor/file.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * AppArmor security module
   4  *
   5  * This file contains AppArmor mediation of files
   6  *
   7  * Copyright (C) 1998-2008 Novell/SUSE
   8  * Copyright 2009-2010 Canonical Ltd.
   9  */
  10
  11 #include <linux/tty.h>
  12 #include <linux/fdtable.h>
  13 #include <linux/file.h>
  14
  15 #include "include/apparmor.h"
  16 #include "include/audit.h"
  17 #include "include/cred.h"
  18 #include "include/file.h"
  19 #include "include/match.h"
  20 #include "include/net.h"
  21 #include "include/path.h"
  22 #include "include/policy.h"
  23 #include "include/label.h"
  24
  25 static u32 map_mask_to_chr_mask(u32 mask)
  26 {
  27         u32 m = mask & PERMS_CHRS_MASK;
  28
  29         if (mask & AA_MAY_GETATTR)
  30                 m |= MAY_READ;
  31         if (mask & (AA_MAY_SETATTR | AA_MAY_CHMOD | AA_MAY_CHOWN))
  32                 m |= MAY_WRITE;
  33
  34         return m;
  35 }
  36
  37 /**
  38  * audit_file_mask - convert mask to permission string
  39  * @buffer: buffer to write string to (NOT NULL)
  40  * @mask: permission mask to convert
  41  */
  42 static void audit_file_mask(struct audit_buffer *ab, u32 mask)
  43 {
  44         char str[10];
  45
  46         aa_perm_mask_to_str(str, sizeof(str), aa_file_perm_chrs,
  47                             map_mask_to_chr_mask(mask));
  48         audit_log_string(ab, str);
  49 }
  50
  51 /**
  52  * file_audit_cb - call back for file specific audit fields
  53  * @ab: audit_buffer  (NOT NULL)
  54  * @va: audit struct to audit values of  (NOT NULL)
  55  */
  56 static void file_audit_cb(struct audit_buffer *ab, void *va)
  57 {
  58         struct common_audit_data *sa = va;
  59         kuid_t fsuid = current_fsuid();
  60
  61         if (aad(sa)->request & AA_AUDIT_FILE_MASK) {
  62                 audit_log_format(ab, " requested_mask=");
  63                 audit_file_mask(ab, aad(sa)->request);
  64         }
  65         if (aad(sa)->denied & AA_AUDIT_FILE_MASK) {
  66                 audit_log_format(ab, " denied_mask=");
  67                 audit_file_mask(ab, aad(sa)->denied);
  68         }
  69         if (aad(sa)->request & AA_AUDIT_FILE_MASK) {
  70                 audit_log_format(ab, " fsuid=%d",
  71                                  from_kuid(&init_user_ns, fsuid));
  72                 audit_log_format(ab, " ouid=%d",
  73                                  from_kuid(&init_user_ns, aad(sa)->fs.ouid));
  74         }
  75
  76         if (aad(sa)->peer) {
  77                 audit_log_format(ab, " target=");
  78                 aa_label_xaudit(ab, labels_ns(aad(sa)->label), aad(sa)->peer,
  79                                 FLAG_VIEW_SUBNS, GFP_ATOMIC);
  80         } else if (aad(sa)->fs.target) {
  81                 audit_log_format(ab, " target=");
  82                 audit_log_untrustedstring(ab, aad(sa)->fs.target);
  83         }
  84 }
  85
  86 /**
  87  * aa_audit_file - handle the auditing of file operations
  88  * @profile: the profile being enforced  (NOT NULL)
  89  * @perms: the permissions computed for the request (NOT NULL)
  90  * @op: operation being mediated
  91  * @request: permissions requested
  92  * @name: name of object being mediated (MAYBE NULL)
  93  * @target: name of target (MAYBE NULL)
  94  * @tlabel: target label (MAY BE NULL)
  95  * @ouid: object uid
  96  * @info: extra information message (MAYBE NULL)
  97  * @error: 0 if operation allowed else failure error code
  98  *
  99  * Returns: %0 or error on failure
 100  */
 101 int aa_audit_file(struct aa_profile *profile, struct aa_perms *perms,
 102                   const char *op, u32 request, const char *name,
 103                   const char *target, struct aa_label *tlabel,
 104                   kuid_t ouid, const char *info, int error)
 105 {
 106         int type = AUDIT_APPARMOR_AUTO;
 107         DEFINE_AUDIT_DATA(sa, LSM_AUDIT_DATA_TASK, op);
 108
 109         sa.u.tsk = NULL;
 110         aad(&sa)->request = request;
 111         aad(&sa)->name = name;
 112         aad(&sa)->fs.target = target;
 113         aad(&sa)->peer = tlabel;
 114         aad(&sa)->fs.ouid = ouid;
 115         aad(&sa)->info = info;
 116         aad(&sa)->error = error;
 117         sa.u.tsk = NULL;
 118
 119         if (likely(!aad(&sa)->error)) {
 120                 u32 mask = perms->audit;
 121
 122                 if (unlikely(AUDIT_MODE(profile) == AUDIT_ALL))
 123                         mask = 0xffff;
 124
 125                 /* mask off perms that are not being force audited */
 126                 aad(&sa)->request &= mask;
 127
 128                 if (likely(!aad(&sa)->request))
 129                         return 0;
 130                 type = AUDIT_APPARMOR_AUDIT;
 131         } else {
 132                 /* only report permissions that were denied */
 133                 aad(&sa)->request = aad(&sa)->request & ~perms->allow;
 134                 AA_BUG(!aad(&sa)->request);
 135
 136                 if (aad(&sa)->request & perms->kill)
 137                         type = AUDIT_APPARMOR_KILL;
 138
 139                 /* quiet known rejects, assumes quiet and kill do not overlap */
 140                 if ((aad(&sa)->request & perms->quiet) &&
 141                     AUDIT_MODE(profile) != AUDIT_NOQUIET &&
 142                     AUDIT_MODE(profile) != AUDIT_ALL)
 143                         aad(&sa)->request &= ~perms->quiet;
 144
 145                 if (!aad(&sa)->request)
 146                         return aad(&sa)->error;
 147         }
 148
 149         aad(&sa)->denied = aad(&sa)->request & ~perms->allow;
 150         return aa_audit(type, profile, &sa, file_audit_cb);
 151 }
 152
 153 /**
 154  * is_deleted - test if a file has been completely unlinked
 155  * @dentry: dentry of file to test for deletion  (NOT NULL)
 156  *
 157  * Returns: %1 if deleted else %0
 158  */
 159 static inline bool is_deleted(struct dentry *dentry)
 160 {
 161         if (d_unlinked(dentry) && d_backing_inode(dentry)->i_nlink == 0)
 162                 return 1;
 163         return 0;
 164 }
 165
 166 static int path_name(const char *op, struct aa_label *label,
 167                      const struct path *path, int flags, char *buffer,
 168                      const char **name, struct path_cond *cond, u32 request)
 169 {
 170         struct aa_profile *profile;
 171         const char *info = NULL;
 172         int error;
 173
 174         error = aa_path_name(path, flags, buffer, name, &info,
 175                              labels_profile(label)->disconnected);
 176         if (error) {
 177                 fn_for_each_confined(label, profile,
 178                         aa_audit_file(profile, &nullperms, op, request, *name,
 179                                       NULL, NULL, cond->uid, info, error));
 180                 return error;
 181         }
 182
 183         return 0;
 184 }
 185
 186 /**
 187  * map_old_perms - map old file perms layout to the new layout
 188  * @old: permission set in old mapping
 189  *
 190  * Returns: new permission mapping
 191  */
 192 static u32 map_old_perms(u32 old)
 193 {
 194         u32 new = old & 0xf;
 195         if (old & MAY_READ)
 196                 new |= AA_MAY_GETATTR | AA_MAY_OPEN;
 197         if (old & MAY_WRITE)
 198                 new |= AA_MAY_SETATTR | AA_MAY_CREATE | AA_MAY_DELETE |
 199                        AA_MAY_CHMOD | AA_MAY_CHOWN | AA_MAY_OPEN;
 200         if (old & 0x10)
 201                 new |= AA_MAY_LINK;
 202         /* the old mapping lock and link_subset flags where overlaid
 203          * and use was determined by part of a pair that they were in
 204          */
 205         if (old & 0x20)
 206                 new |= AA_MAY_LOCK | AA_LINK_SUBSET;
 207         if (old & 0x40) /* AA_EXEC_MMAP */
 208                 new |= AA_EXEC_MMAP;
 209
 210         return new;
 211 }
 212
 213 /**
 214  * aa_compute_fperms - convert dfa compressed perms to internal perms
 215  * @dfa: dfa to compute perms for   (NOT NULL)
 216  * @state: state in dfa
 217  * @cond:  conditions to consider  (NOT NULL)
 218  *
 219  * TODO: convert from dfa + state to permission entry, do computation conversion
 220  *       at load time.
 221  *
 222  * Returns: computed permission set
 223  */
 224 struct aa_perms aa_compute_fperms(struct aa_dfa *dfa, unsigned int state,
 225                                   struct path_cond *cond)
 226 {
 227         /* FIXME: change over to new dfa format
 228          * currently file perms are encoded in the dfa, new format
 229          * splits the permissions from the dfa.  This mapping can be
 230          * done at profile load
 231          */
 232         struct aa_perms perms = { };
 233
 234         if (uid_eq(current_fsuid(), cond->uid)) {
 235                 perms.allow = map_old_perms(dfa_user_allow(dfa, state));
 236                 perms.audit = map_old_perms(dfa_user_audit(dfa, state));
 237                 perms.quiet = map_old_perms(dfa_user_quiet(dfa, state));
 238                 perms.xindex = dfa_user_xindex(dfa, state);
 239         } else {
 240                 perms.allow = map_old_perms(dfa_other_allow(dfa, state));
 241                 perms.audit = map_old_perms(dfa_other_audit(dfa, state));
 242                 perms.quiet = map_old_perms(dfa_other_quiet(dfa, state));
 243                 perms.xindex = dfa_other_xindex(dfa, state);
 244         }
 245         perms.allow |= AA_MAY_GETATTR;
 246
 247         /* change_profile wasn't determined by ownership in old mapping */
 248         if (ACCEPT_TABLE(dfa)[state] & 0x80000000)
 249                 perms.allow |= AA_MAY_CHANGE_PROFILE;
 250         if (ACCEPT_TABLE(dfa)[state] & 0x40000000)
 251                 perms.allow |= AA_MAY_ONEXEC;
 252
 253         return perms;
 254 }
 255
 256 /**
 257  * aa_str_perms - find permission that match @name
 258  * @dfa: to match against  (MAYBE NULL)
 259  * @state: state to start matching in
 260  * @name: string to match against dfa  (NOT NULL)
 261  * @cond: conditions to consider for permission set computation  (NOT NULL)
 262  * @perms: Returns - the permissions found when matching @name
 263  *
 264  * Returns: the final state in @dfa when beginning @start and walking @name
 265  */
 266 unsigned int aa_str_perms(struct aa_dfa *dfa, unsigned int start,
 267                           const char *name, struct path_cond *cond,
 268                           struct aa_perms *perms)
 269 {
 270         unsigned int state;
 271         state = aa_dfa_match(dfa, start, name);
 272         *perms = aa_compute_fperms(dfa, state, cond);
 273
 274         return state;
 275 }
 276
 277 int __aa_path_perm(const char *op, struct aa_profile *profile, const char *name,
 278                    u32 request, struct path_cond *cond, int flags,
 279                    struct aa_perms *perms)
 280 {
 281         int e = 0;
 282
 283         if (profile_unconfined(profile))
 284                 return 0;
 285         aa_str_perms(profile->file.dfa, profile->file.start, name, cond, perms);
 286         if (request & ~perms->allow)
 287                 e = -EACCES;
 288         return aa_audit_file(profile, perms, op, request, name, NULL, NULL,
 289                              cond->uid, NULL, e);
 290 }
 291
 292
 293 static int profile_path_perm(const char *op, struct aa_profile *profile,
 294                              const struct path *path, char *buffer, u32 request,
 295                              struct path_cond *cond, int flags,
 296                              struct aa_perms *perms)
 297 {
 298         const char *name;
 299         int error;
 300
 301         if (profile_unconfined(profile))
 302                 return 0;
 303
 304         error = path_name(op, &profile->label, path,
 305                           flags | profile->path_flags, buffer, &name, cond,
 306                           request);
 307         if (error)
 308                 return error;
 309         return __aa_path_perm(op, profile, name, request, cond, flags,
 310                               perms);
 311 }
 312
 313 /**
 314  * aa_path_perm - do permissions check & audit for @path
 315  * @op: operation being checked
 316  * @label: profile being enforced  (NOT NULL)
 317  * @path: path to check permissions of  (NOT NULL)
 318  * @flags: any additional path flags beyond what the profile specifies
 319  * @request: requested permissions
 320  * @cond: conditional info for this request  (NOT NULL)
 321  *
 322  * Returns: %0 else error if access denied or other error
 323  */
 324 int aa_path_perm(const char *op, struct aa_label *label,
 325                  const struct path *path, int flags, u32 request,
 326                  struct path_cond *cond)
 327 {
 328         struct aa_perms perms = {};
 329         struct aa_profile *profile;
 330         char *buffer = NULL;
 331         int error;
 332
 333         flags |= PATH_DELEGATE_DELETED | (S_ISDIR(cond->mode) ? PATH_IS_DIR :
 334                                                                 0);
 335         get_buffers(buffer);
 336         error = fn_for_each_confined(label, profile,
 337                         profile_path_perm(op, profile, path, buffer, request,
 338                                           cond, flags, &perms));
 339
 340         put_buffers(buffer);
 341
 342         return error;
 343 }
 344
 345 /**
 346  * xindex_is_subset - helper for aa_path_link
 347  * @link: link permission set
 348  * @target: target permission set
 349  *
 350  * test target x permissions are equal OR a subset of link x permissions
 351  * this is done as part of the subset test, where a hardlink must have
 352  * a subset of permissions that the target has.
 353  *
 354  * Returns: %1 if subset else %0
 355  */
 356 static inline bool xindex_is_subset(u32 link, u32 target)
 357 {
 358         if (((link & ~AA_X_UNSAFE) != (target & ~AA_X_UNSAFE)) ||
 359             ((link & AA_X_UNSAFE) && !(target & AA_X_UNSAFE)))
 360                 return 0;
 361
 362         return 1;
 363 }
 364
 365 static int profile_path_link(struct aa_profile *profile,
 366                              const struct path *link, char *buffer,
 367                              const struct path *target, char *buffer2,
 368                              struct path_cond *cond)
 369 {
 370         const char *lname, *tname = NULL;
 371         struct aa_perms lperms = {}, perms;
 372         const char *info = NULL;
 373         u32 request = AA_MAY_LINK;
 374         unsigned int state;
 375         int error;
 376
 377         error = path_name(OP_LINK, &profile->label, link, profile->path_flags,
 378                           buffer, &lname, cond, AA_MAY_LINK);
 379         if (error)
 380                 goto audit;
 381
 382         /* buffer2 freed below, tname is pointer in buffer2 */
 383         error = path_name(OP_LINK, &profile->label, target, profile->path_flags,
 384                           buffer2, &tname, cond, AA_MAY_LINK);
 385         if (error)
 386                 goto audit;
 387
 388         error = -EACCES;
 389         /* aa_str_perms - handles the case of the dfa being NULL */
 390         state = aa_str_perms(profile->file.dfa, profile->file.start, lname,
 391                              cond, &lperms);
 392
 393         if (!(lperms.allow & AA_MAY_LINK))
 394                 goto audit;
 395
 396         /* test to see if target can be paired with link */
 397         state = aa_dfa_null_transition(profile->file.dfa, state);
 398         aa_str_perms(profile->file.dfa, state, tname, cond, &perms);
 399
 400         /* force audit/quiet masks for link are stored in the second entry
 401          * in the link pair.
 402          */
 403         lperms.audit = perms.audit;
 404         lperms.quiet = perms.quiet;
 405         lperms.kill = perms.kill;
 406
 407         if (!(perms.allow & AA_MAY_LINK)) {
 408                 info = "target restricted";
 409                 lperms = perms;
 410                 goto audit;
 411         }
 412
 413         /* done if link subset test is not required */
 414         if (!(perms.allow & AA_LINK_SUBSET))
 415                 goto done_tests;
 416
 417         /* Do link perm subset test requiring allowed permission on link are
 418          * a subset of the allowed permissions on target.
 419          */
 420         aa_str_perms(profile->file.dfa, profile->file.start, tname, cond,
 421                      &perms);
 422
 423         /* AA_MAY_LINK is not considered in the subset test */
 424         request = lperms.allow & ~AA_MAY_LINK;
 425         lperms.allow &= perms.allow | AA_MAY_LINK;
 426
 427         request |= AA_AUDIT_FILE_MASK & (lperms.allow & ~perms.allow);
 428         if (request & ~lperms.allow) {
 429                 goto audit;
 430         } else if ((lperms.allow & MAY_EXEC) &&
 431                    !xindex_is_subset(lperms.xindex, perms.xindex)) {
 432                 lperms.allow &= ~MAY_EXEC;
 433                 request |= MAY_EXEC;
 434                 info = "link not subset of target";
 435                 goto audit;
 436         }
 437
 438 done_tests:
 439         error = 0;
 440
 441 audit:
 442         return aa_audit_file(profile, &lperms, OP_LINK, request, lname, tname,
 443                              NULL, cond->uid, info, error);
 444 }
 445
 446 /**
 447  * aa_path_link - Handle hard link permission check
 448  * @label: the label being enforced  (NOT NULL)
 449  * @old_dentry: the target dentry  (NOT NULL)
 450  * @new_dir: directory the new link will be created in  (NOT NULL)
 451  * @new_dentry: the link being created  (NOT NULL)
 452  *
 453  * Handle the permission test for a link & target pair.  Permission
 454  * is encoded as a pair where the link permission is determined
 455  * first, and if allowed, the target is tested.  The target test
 456  * is done from the point of the link match (not start of DFA)
 457  * making the target permission dependent on the link permission match.
 458  *
 459  * The subset test if required forces that permissions granted
 460  * on link are a subset of the permission granted to target.
 461  *
 462  * Returns: %0 if allowed else error
 463  */
 464 int aa_path_link(struct aa_label *label, struct dentry *old_dentry,
 465                  const struct path *new_dir, struct dentry *new_dentry)
 466 {
 467         struct path link = { .mnt = new_dir->mnt, .dentry = new_dentry };
 468         struct path target = { .mnt = new_dir->mnt, .dentry = old_dentry };
 469         struct path_cond cond = {
 470                 d_backing_inode(old_dentry)->i_uid,
 471                 d_backing_inode(old_dentry)->i_mode
 472         };
 473         char *buffer = NULL, *buffer2 = NULL;
 474         struct aa_profile *profile;
 475         int error;
 476
 477         /* buffer freed below, lname is pointer in buffer */
 478         get_buffers(buffer, buffer2);
 479         error = fn_for_each_confined(label, profile,
 480                         profile_path_link(profile, &link, buffer, &target,
 481                                           buffer2, &cond));
 482         put_buffers(buffer, buffer2);
 483
 484         return error;
 485 }
 486
 487 static void update_file_ctx(struct aa_file_ctx *fctx, struct aa_label *label,
 488                             u32 request)
 489 {
 490         struct aa_label *l, *old;
 491
 492         /* update caching of label on file_ctx */
 493         spin_lock(&fctx->lock);
 494         old = rcu_dereference_protected(fctx->label,
 495                                         lockdep_is_held(&fctx->lock));
 496         l = aa_label_merge(old, label, GFP_ATOMIC);
 497         if (l) {
 498                 if (l != old) {
 499                         rcu_assign_pointer(fctx->label, l);
 500                         aa_put_label(old);
 501                 } else
 502                         aa_put_label(l);
 503                 fctx->allow |= request;
 504         }
 505         spin_unlock(&fctx->lock);
 506 }
 507
 508 static int __file_path_perm(const char *op, struct aa_label *label,
 509                             struct aa_label *flabel, struct file *file,
 510                             u32 request, u32 denied)
 511 {
 512         struct aa_profile *profile;
 513         struct aa_perms perms = {};
 514         struct path_cond cond = {
 515                 .uid = file_inode(file)->i_uid,
 516                 .mode = file_inode(file)->i_mode
 517         };
 518         char *buffer;
 519         int flags, error;
 520
 521         /* revalidation due to label out of date. No revocation at this time */
 522         if (!denied && aa_label_is_subset(flabel, label))
 523                 /* TODO: check for revocation on stale profiles */
 524                 return 0;
 525
 526         flags = PATH_DELEGATE_DELETED | (S_ISDIR(cond.mode) ? PATH_IS_DIR : 0);
 527         get_buffers(buffer);
 528
 529         /* check every profile in task label not in current cache */
 530         error = fn_for_each_not_in_set(flabel, label, profile,
 531                         profile_path_perm(op, profile, &file->f_path, buffer,
 532                                           request, &cond, flags, &perms));
 533         if (denied && !error) {
 534                 /*
 535                  * check every profile in file label that was not tested
 536                  * in the initial check above.
 537                  *
 538                  * TODO: cache full perms so this only happens because of
 539                  * conditionals
 540                  * TODO: don't audit here
 541                  */
 542                 if (label == flabel)
 543                         error = fn_for_each(label, profile,
 544                                 profile_path_perm(op, profile, &file->f_path,
 545                                                   buffer, request, &cond, flags,
 546                                                   &perms));
 547                 else
 548                         error = fn_for_each_not_in_set(label, flabel, profile,
 549                                 profile_path_perm(op, profile, &file->f_path,
 550                                                   buffer, request, &cond, flags,
 551                                                   &perms));
 552         }
 553         if (!error)
 554                 update_file_ctx(file_ctx(file), label, request);
 555
 556         put_buffers(buffer);
 557
 558         return error;
 559 }
 560
 561 static int __file_sock_perm(const char *op, struct aa_label *label,
 562                             struct aa_label *flabel, struct file *file,
 563                             u32 request, u32 denied)
 564 {
 565         struct socket *sock = (struct socket *) file->private_data;
 566         int error;
 567
 568         AA_BUG(!sock);
 569
 570         /* revalidation due to label out of date. No revocation at this time */
 571         if (!denied && aa_label_is_subset(flabel, label))
 572                 return 0;
 573
 574         /* TODO: improve to skip profiles cached in flabel */
 575         error = aa_sock_file_perm(label, op, request, sock);
 576         if (denied) {
 577                 /* TODO: improve to skip profiles checked above */
 578                 /* check every profile in file label to is cached */
 579                 last_error(error, aa_sock_file_perm(flabel, op, request, sock));
 580         }
 581         if (!error)
 582                 update_file_ctx(file_ctx(file), label, request);
 583
 584         return error;
 585 }
 586
 587 /**
 588  * aa_file_perm - do permission revalidation check & audit for @file
 589  * @op: operation being checked
 590  * @label: label being enforced   (NOT NULL)
 591  * @file: file to revalidate access permissions on  (NOT NULL)
 592  * @request: requested permissions
 593  *
 594  * Returns: %0 if access allowed else error
 595  */
 596 int aa_file_perm(const char *op, struct aa_label *label, struct file *file,
 597                  u32 request)
 598 {
 599         struct aa_file_ctx *fctx;
 600         struct aa_label *flabel;
 601         u32 denied;
 602         int error = 0;
 603
 604         AA_BUG(!label);
 605         AA_BUG(!file);
 606
 607         fctx = file_ctx(file);
 608
 609         rcu_read_lock();
 610         flabel  = rcu_dereference(fctx->label);
 611         AA_BUG(!flabel);
 612
 613         /* revalidate access, if task is unconfined, or the cached cred
 614          * doesn't match or if the request is for more permissions than
 615          * was granted.
 616          *
 617          * Note: the test for !unconfined(flabel) is to handle file
 618          *       delegation from unconfined tasks
 619          */
 620         denied = request & ~fctx->allow;
 621         if (unconfined(label) || unconfined(flabel) ||
 622             (!denied && aa_label_is_subset(flabel, label)))
 623                 goto done;
 624
 625         /* TODO: label cross check */
 626
 627         if (file->f_path.mnt && path_mediated_fs(file->f_path.dentry))
 628                 error = __file_path_perm(op, label, flabel, file, request,
 629                                          denied);
 630
 631         else if (S_ISSOCK(file_inode(file)->i_mode))
 632                 error = __file_sock_perm(op, label, flabel, file, request,
 633                                          denied);
 634 done:
 635         rcu_read_unlock();
 636
 637         return error;
 638 }
 639
 640 static void revalidate_tty(struct aa_label *label)
 641 {
 642         struct tty_struct *tty;
 643         int drop_tty = 0;
 644
 645         tty = get_current_tty();
 646         if (!tty)
 647                 return;
 648
 649         spin_lock(&tty->files_lock);
 650         if (!list_empty(&tty->tty_files)) {
 651                 struct tty_file_private *file_priv;
 652                 struct file *file;
 653                 /* TODO: Revalidate access to controlling tty. */
 654                 file_priv = list_first_entry(&tty->tty_files,
 655                                              struct tty_file_private, list);
 656                 file = file_priv->file;
 657
 658                 if (aa_file_perm(OP_INHERIT, label, file, MAY_READ | MAY_WRITE))
 659                         drop_tty = 1;
 660         }
 661         spin_unlock(&tty->files_lock);
 662         tty_kref_put(tty);
 663
 664         if (drop_tty)
 665                 no_tty();
 666 }
 667
 668 static int match_file(const void *p, struct file *file, unsigned int fd)
 669 {
 670         struct aa_label *label = (struct aa_label *)p;
 671
 672         if (aa_file_perm(OP_INHERIT, label, file, aa_map_file_to_perms(file)))
 673                 return fd + 1;
 674         return 0;
 675 }
 676
 677
 678 /* based on selinux's flush_unauthorized_files */
 679 void aa_inherit_files(const struct cred *cred, struct files_struct *files)
 680 {
 681         struct aa_label *label = aa_get_newest_cred_label(cred);
 682         struct file *devnull = NULL;
 683         unsigned int n;
 684
 685         revalidate_tty(label);
 686
 687         /* Revalidate access to inherited open files. */
 688         n = iterate_fd(files, 0, match_file, label);
 689         if (!n) /* none found? */
 690                 goto out;
 691
 692         devnull = dentry_open(&aa_null, O_RDWR, cred);
 693         if (IS_ERR(devnull))
 694                 devnull = NULL;
 695         /* replace all the matching ones with this */
 696         do {
 697                 replace_fd(n - 1, devnull, 0);
 698         } while ((n = iterate_fd(files, n, match_file, label)) != 0);
 699         if (devnull)
 700                 fput(devnull);
 701 out:
 702         aa_put_label(label);
 703 }