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/af_unix.h"
  20 #include "include/apparmor.h"
  21 #include "include/audit.h"
  22 #include "include/context.h"
  23 #include "include/file.h"
  24 #include "include/match.h"
  25 #include "include/path.h"
  26 #include "include/policy.h"
  27 #include "include/label.h"
  28
  29 static u32 map_mask_to_chr_mask(u32 mask)
  30 {
  31         u32 m = mask & PERMS_CHRS_MASK;
  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
 110         DEFINE_AUDIT_DATA(sa, LSM_AUDIT_DATA_TASK, op);
 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                      bool delegate_deleted)
 172 {
 173         struct aa_profile *profile;
 174         const char *info = NULL;
 175         int error = aa_path_name(path, flags, buffer, name, &info,
 176                                  labels_profile(label)->disconnected);
 177         if (error) {
 178                 if (error == -ENOENT && is_deleted(path->dentry) &&
 179                     delegate_deleted)
 180                         return 0;
 181                 fn_for_each_confined(label, profile,
 182                         aa_audit_file(profile, &nullperms, op, request, *name,
 183                                       NULL, NULL, cond->uid, info, error));
 184                 return error;
 185         }
 186
 187         return 0;
 188 }
 189
 190 /**
 191  * map_old_perms - map old file perms layout to the new layout
 192  * @old: permission set in old mapping
 193  *
 194  * Returns: new permission mapping
 195  */
 196 static u32 map_old_perms(u32 old)
 197 {
 198         u32 new = old & 0xf;
 199         if (old & MAY_READ)
 200                 new |= AA_MAY_GETATTR | AA_MAY_OPEN;
 201         if (old & MAY_WRITE)
 202                 new |= AA_MAY_SETATTR | AA_MAY_CREATE | AA_MAY_DELETE |
 203                         AA_MAY_CHMOD | AA_MAY_CHOWN | AA_MAY_OPEN |
 204                         AA_MAY_DELETE;
 205         if (old & 0x10)
 206                 new |= AA_MAY_LINK;
 207         /* the old mapping lock and link_subset flags where overlaid
 208          * and use was determined by part of a pair that they were in
 209          */
 210         if (old & 0x20)
 211                 new |= AA_MAY_LOCK | AA_LINK_SUBSET;
 212         if (old & 0x40) /* AA_EXEC_MMAP */
 213                 new |= AA_EXEC_MMAP;
 214
 215         return new;
 216 }
 217
 218 /**
 219  * aa_compute_fperms - convert dfa compressed perms to internal perms
 220  * @dfa: dfa to compute perms for   (NOT NULL)
 221  * @state: state in dfa
 222  * @cond:  conditions to consider  (NOT NULL)
 223  *
 224  * TODO: convert from dfa + state to permission entry, do computation conversion
 225  *       at load time.
 226  *
 227  * Returns: computed permission set
 228  */
 229 struct aa_perms aa_compute_fperms(struct aa_dfa *dfa, unsigned int state,
 230                                   struct path_cond *cond)
 231 {
 232         struct aa_perms perms;
 233
 234         /* FIXME: change over to new dfa format
 235          * currently file perms are encoded in the dfa, new format
 236          * splits the permissions from the dfa.  This mapping can be
 237          * done at profile load
 238          */
 239         perms.deny = 0;
 240         perms.kill = perms.stop = 0;
 241         perms.complain = perms.cond = 0;
 242         perms.hide = 0;
 243         perms.prompt = 0;
 244
 245         if (uid_eq(current_fsuid(), cond->uid)) {
 246                 perms.allow = map_old_perms(dfa_user_allow(dfa, state));
 247                 perms.audit = map_old_perms(dfa_user_audit(dfa, state));
 248                 perms.quiet = map_old_perms(dfa_user_quiet(dfa, state));
 249                 perms.xindex = dfa_user_xindex(dfa, state);
 250         } else {
 251                 perms.allow = map_old_perms(dfa_other_allow(dfa, state));
 252                 perms.audit = map_old_perms(dfa_other_audit(dfa, state));
 253                 perms.quiet = map_old_perms(dfa_other_quiet(dfa, state));
 254                 perms.xindex = dfa_other_xindex(dfa, state);
 255         }
 256         perms.allow |= AA_MAY_GETATTR;
 257
 258         /* change_profile wasn't determined by ownership in old mapping */
 259         if (ACCEPT_TABLE(dfa)[state] & 0x80000000)
 260                 perms.allow |= AA_MAY_CHANGE_PROFILE;
 261         if (ACCEPT_TABLE(dfa)[state] & 0x40000000)
 262                 perms.allow |= AA_MAY_ONEXEC;
 263
 264         return perms;
 265 }
 266
 267 /**
 268  * aa_str_perms - find permission that match @name
 269  * @dfa: to match against  (MAYBE NULL)
 270  * @state: state to start matching in
 271  * @name: string to match against dfa  (NOT NULL)
 272  * @cond: conditions to consider for permission set computation  (NOT NULL)
 273  * @perms: Returns - the permissions found when matching @name
 274  *
 275  * Returns: the final state in @dfa when beginning @start and walking @name
 276  */
 277 unsigned int aa_str_perms(struct aa_dfa *dfa, unsigned int start,
 278                           const char *name, struct path_cond *cond,
 279                           struct aa_perms *perms)
 280 {
 281         unsigned int state;
 282         state = aa_dfa_match(dfa, start, name);
 283         *perms = aa_compute_fperms(dfa, state, cond);
 284
 285         return state;
 286 }
 287
 288 int __aa_path_perm(const char *op, struct aa_profile *profile, const char *name,
 289                    u32 request, struct path_cond *cond, int flags,
 290                    struct aa_perms *perms)
 291 {
 292         int e = 0;
 293         if (profile_unconfined(profile) ||
 294             ((flags & PATH_SOCK_COND) && !PROFILE_MEDIATES_AF(profile, AF_UNIX)))
 295                 return 0;
 296         aa_str_perms(profile->file.dfa, profile->file.start, name, cond, perms);
 297         if (request & ~perms->allow)
 298                 e = -EACCES;
 299         return aa_audit_file(profile, perms, op, request, name, NULL, NULL,
 300                              cond->uid, NULL, e);
 301 }
 302
 303 /**
 304  * aa_path_perm - do permissions check & audit for @path
 305  * @op: operation being checked
 306  * @label: profile being enforced  (NOT NULL)
 307  * @path: path to check permissions of  (NOT NULL)
 308  * @flags: any additional path flags beyond what the profile specifies
 309  * @request: requested permissions
 310  * @cond: conditional info for this request  (NOT NULL)
 311  *
 312  * Returns: %0 else error if access denied or other error
 313  */
 314 int aa_path_perm(const char *op, struct aa_label *label,
 315                  const struct path *path, int flags, u32 request,
 316                  struct path_cond *cond)
 317 {
 318         struct aa_perms perms = {};
 319         char *buffer = NULL;
 320         const char *name;
 321         struct aa_profile *profile;
 322         int error;
 323
 324         /* TODO: fix path lookup flags */
 325         flags |= labels_profile(label)->path_flags |
 326                 (S_ISDIR(cond->mode) ? PATH_IS_DIR : 0);
 327         get_buffers(buffer);
 328
 329         error = path_name(op, label, path, flags, buffer, &name, cond,
 330                           request, true);
 331         if (!error)
 332                 error = fn_for_each_confined(label, profile,
 333                                 __aa_path_perm(op, profile, name, request, cond,
 334                                                flags, &perms));
 335
 336         put_buffers(buffer);
 337         return error;
 338 }
 339
 340 /**
 341  * xindex_is_subset - helper for aa_path_link
 342  * @link: link permission set
 343  * @target: target permission set
 344  *
 345  * test target x permissions are equal OR a subset of link x permissions
 346  * this is done as part of the subset test, where a hardlink must have
 347  * a subset of permissions that the target has.
 348  *
 349  * Returns: %1 if subset else %0
 350  */
 351 static inline bool xindex_is_subset(u32 link, u32 target)
 352 {
 353         if (((link & ~AA_X_UNSAFE) != (target & ~AA_X_UNSAFE)) ||
 354             ((link & AA_X_UNSAFE) && !(target & AA_X_UNSAFE)))
 355                 return 0;
 356
 357         return 1;
 358 }
 359
 360 static int profile_path_link(struct aa_profile *profile, const char *lname,
 361                              const char *tname, struct path_cond *cond)
 362 {
 363         struct aa_perms lperms, perms;
 364         const char *info = NULL;
 365         u32 request = AA_MAY_LINK;
 366         unsigned int state;
 367         int e = -EACCES;
 368
 369         /* aa_str_perms - handles the case of the dfa being NULL */
 370         state = aa_str_perms(profile->file.dfa, profile->file.start, lname,
 371                              cond, &lperms);
 372
 373         if (!(lperms.allow & AA_MAY_LINK))
 374                 goto audit;
 375
 376         /* test to see if target can be paired with link */
 377         state = aa_dfa_null_transition(profile->file.dfa, state);
 378         aa_str_perms(profile->file.dfa, state, tname, cond, &perms);
 379
 380         /* force audit/quiet masks for link are stored in the second entry
 381          * in the link pair.
 382          */
 383         lperms.audit = perms.audit;
 384         lperms.quiet = perms.quiet;
 385         lperms.kill = perms.kill;
 386
 387         if (!(perms.allow & AA_MAY_LINK)) {
 388                 info = "target restricted";
 389                 lperms = perms;
 390                 goto audit;
 391         }
 392
 393         /* done if link subset test is not required */
 394         if (!(perms.allow & AA_LINK_SUBSET))
 395                 goto done_tests;
 396
 397         /* Do link perm subset test requiring allowed permission on link are
 398          * a subset of the allowed permissions on target.
 399          */
 400         aa_str_perms(profile->file.dfa, profile->file.start, tname, cond,
 401                      &perms);
 402
 403         /* AA_MAY_LINK is not considered in the subset test */
 404         request = lperms.allow & ~AA_MAY_LINK;
 405         lperms.allow &= perms.allow | AA_MAY_LINK;
 406
 407         request |= AA_AUDIT_FILE_MASK & (lperms.allow & ~perms.allow);
 408         if (request & ~lperms.allow) {
 409                 goto audit;
 410         } else if ((lperms.allow & MAY_EXEC) &&
 411                    !xindex_is_subset(lperms.xindex, perms.xindex)) {
 412                 lperms.allow &= ~MAY_EXEC;
 413                 request |= MAY_EXEC;
 414                 info = "link not subset of target";
 415                 goto audit;
 416         }
 417
 418 done_tests:
 419         e = 0;
 420
 421 audit:
 422         return aa_audit_file(profile, &lperms, OP_LINK, request, lname, tname,
 423                              NULL, cond->uid, info, e);
 424 }
 425
 426 /**
 427  * aa_path_link - Handle hard link permission check
 428  * @label: the label being enforced  (NOT NULL)
 429  * @old_dentry: the target dentry  (NOT NULL)
 430  * @new_dir: directory the new link will be created in  (NOT NULL)
 431  * @new_dentry: the link being created  (NOT NULL)
 432  *
 433  * Handle the permission test for a link & target pair.  Permission
 434  * is encoded as a pair where the link permission is determined
 435  * first, and if allowed, the target is tested.  The target test
 436  * is done from the point of the link match (not start of DFA)
 437  * making the target permission dependent on the link permission match.
 438  *
 439  * The subset test if required forces that permissions granted
 440  * on link are a subset of the permission granted to target.
 441  *
 442  * Returns: %0 if allowed else error
 443  */
 444 int aa_path_link(struct aa_label *label, struct dentry *old_dentry,
 445                  const struct path *new_dir, struct dentry *new_dentry)
 446 {
 447         struct path link = { new_dir->mnt, new_dentry };
 448         struct path target = { new_dir->mnt, old_dentry };
 449         struct path_cond cond = {
 450                 d_backing_inode(old_dentry)->i_uid,
 451                 d_backing_inode(old_dentry)->i_mode
 452         };
 453         char *buffer = NULL, *buffer2 = NULL;
 454         const char *lname, *tname = NULL;
 455         struct aa_profile *profile;
 456         int error;
 457
 458         /* TODO: fix path lookup flags, auditing of failed path for profile */
 459         profile = labels_profile(label);
 460         /* buffer freed below, lname is pointer in buffer */
 461         get_buffers(buffer, buffer2);
 462         error = path_name(OP_LINK, label, &link,
 463                           labels_profile(label)->path_flags, buffer,
 464                           &lname, &cond, AA_MAY_LINK, false);
 465         if (error)
 466                 goto out;
 467
 468         /* buffer2 freed below, tname is pointer in buffer2 */
 469         error = path_name(OP_LINK, label, &target,
 470                           labels_profile(label)->path_flags, buffer2, &tname,
 471                           &cond, AA_MAY_LINK, false);
 472         if (error)
 473                 goto out;
 474
 475         error = fn_for_each_confined(label, profile,
 476                         profile_path_link(profile, lname, tname, &cond));
 477
 478 out:
 479         put_buffers(buffer, buffer2);
 480
 481         return error;
 482 }
 483
 484 static void update_file_ctx(struct aa_file_ctx *fctx, struct aa_label *label,
 485                             u32 request)
 486 {
 487         struct aa_label *l, *old;
 488
 489         /* update caching of label on file_ctx */
 490         spin_lock(&fctx->lock);
 491         old = rcu_dereference_protected(fctx->label,
 492                                         spin_is_locked(&fctx->lock));
 493         l = aa_label_merge(old, label, GFP_ATOMIC);
 494         if (l) {
 495                 if (l != old) {
 496                         rcu_assign_pointer(fctx->label, l);
 497                         aa_put_label(old);
 498                 } else
 499                         aa_put_label(l);
 500                 fctx->allow |= request;
 501         }
 502         spin_unlock(&fctx->lock);
 503 }
 504
 505 static int __file_path_perm(const char *op, struct aa_label *label,
 506                             struct aa_label *flabel, struct file *file,
 507                             u32 request, u32 denied)
 508 {
 509         struct aa_profile *profile;
 510         struct aa_perms perms = {};
 511         struct path_cond cond = {
 512                 .uid = file_inode(file)->i_uid,
 513                 .mode = file_inode(file)->i_mode
 514         };
 515         const char *name;
 516         char *buffer;
 517         int flags, error;
 518
 519         /* revalidation due to label out of date. No revocation at this time */
 520         if (!denied && aa_label_is_subset(flabel, label))
 521                 /* TODO: check for revocation on stale profiles */
 522                 return 0;
 523
 524         /* TODO: fix path lookup flags */
 525         flags = PATH_DELEGATE_DELETED | labels_profile(label)->path_flags |
 526                 (S_ISDIR(cond.mode) ? PATH_IS_DIR : 0);
 527         get_buffers(buffer);
 528
 529         error = path_name(op, label, &file->f_path, flags, buffer, &name, &cond,
 530                           request, true);
 531         if (error) {
 532                 if (error == 1)
 533                         /* Access to open files that are deleted are
 534                          * given a pass (implicit delegation)
 535                          */
 536                         /* TODO not needed when full perms cached */
 537                         error = 0;
 538                 goto out;
 539         }
 540
 541         /* check every profile in task label not in current cache */
 542         error = fn_for_each_not_in_set(flabel, label, profile,
 543                         __aa_path_perm(op, profile, name, request, &cond, 0,
 544                                        &perms));
 545         if (denied) {
 546                 /* check every profile in file label that was not tested
 547                  * in the initial check above.
 548                  */
 549                 /* TODO: cache full perms so this only happens because of
 550                  * conditionals */
 551                 /* TODO: don't audit here */
 552                 last_error(error,
 553                         fn_for_each_not_in_set(label, flabel, profile,
 554                                 __aa_path_perm(op, profile, name, request,
 555                                                &cond, 0, &perms)));
 556         }
 557         if (!error)
 558                 update_file_ctx(file_ctx(file), label, request);
 559
 560 out:
 561         put_buffers(buffer);
 562
 563         return error;
 564 }
 565
 566 static int __file_sock_perm(const char *op, struct aa_label *label,
 567                             struct aa_label *flabel, struct file *file,
 568                             u32 request, u32 denied)
 569 {
 570         struct socket *sock = (struct socket *) file->private_data;
 571         int error;
 572
 573         AA_BUG(!sock);
 574
 575         /* revalidation due to label out of date. No revocation at this time */
 576         if (!denied && aa_label_is_subset(flabel, label))
 577                 return 0;
 578
 579         /* TODO: improve to skip profiles cached in flabel */
 580         error = aa_sock_file_perm(label, op, request, sock);
 581         if (denied) {
 582                 /* TODO: improve to skip profiles checked above */
 583                 /* check every profile in file label to is cached */
 584                 last_error(error, aa_sock_file_perm(flabel, op, request, sock));
 585         }
 586         if (!error)
 587                 update_file_ctx(file_ctx(file), label, request);
 588
 589         return error;
 590 }
 591
 592 /**
 593  * aa_file_perm - do permission revalidation check & audit for @file
 594  * @op: operation being checked
 595  * @label: label being enforced   (NOT NULL)
 596  * @file: file to revalidate access permissions on  (NOT NULL)
 597  * @request: requested permissions
 598  *
 599  * Returns: %0 if access allowed else error
 600  */
 601 int aa_file_perm(const char *op, struct aa_label *label, struct file *file,
 602                  u32 request)
 603 {
 604         struct aa_file_ctx *fctx;
 605         struct aa_label *flabel;
 606         u32 denied;
 607         int error = 0;
 608
 609         AA_BUG(!label);
 610         AA_BUG(!file);
 611
 612         fctx = file_ctx(file);
 613
 614         rcu_read_lock();
 615         flabel  = rcu_dereference(fctx->label);
 616         AA_BUG(!flabel);
 617
 618         /* revalidate access, if task is unconfined, or the cached cred
 619          * doesn't match or if the request is for more permissions than
 620          * was granted.
 621          *
 622          * Note: the test for !unconfined(flabel) is to handle file
 623          *       delegation from unconfined tasks
 624          */
 625         denied = request & ~fctx->allow;
 626         if (unconfined(label) || unconfined(flabel) ||
 627             (!denied && aa_label_is_subset(flabel, label)))
 628                 goto done;
 629
 630         /* TODO: label cross check */
 631
 632         if (file->f_path.mnt && path_mediated_fs(file->f_path.dentry)) {
 633                 error = __file_path_perm(op, label, flabel, file, request,
 634                                          denied);
 635
 636         } else if (S_ISSOCK(file_inode(file)->i_mode)) {
 637                 error = __file_sock_perm(op, label, flabel, file, request,
 638                                          denied);
 639         }
 640 done:
 641         rcu_read_unlock();
 642
 643         return error;
 644 }
 645
 646 static void revalidate_tty(struct aa_label *label)
 647 {
 648         struct tty_struct *tty;
 649         int drop_tty = 0;
 650
 651         tty = get_current_tty();
 652         if (!tty)
 653                 return;
 654
 655         spin_lock(&tty->files_lock);
 656         if (!list_empty(&tty->tty_files)) {
 657                 struct tty_file_private *file_priv;
 658                 struct file *file;
 659                 /* TODO: Revalidate access to controlling tty. */
 660                 file_priv = list_first_entry(&tty->tty_files,
 661                                              struct tty_file_private, list);
 662                 file = file_priv->file;
 663
 664                 if (aa_file_perm(OP_INHERIT, label, file, MAY_READ | MAY_WRITE))
 665                         drop_tty = 1;
 666         }
 667         spin_unlock(&tty->files_lock);
 668         tty_kref_put(tty);
 669
 670         if (drop_tty)
 671                 no_tty();
 672 }
 673
 674 static int match_file(const void *p, struct file *file, unsigned fd)
 675 {
 676         struct aa_label *label = (struct aa_label *)p;
 677         if (aa_file_perm(OP_INHERIT, label, file, aa_map_file_to_perms(file)))
 678                 return fd + 1;
 679         return 0;
 680 }
 681
 682
 683 /* based on selinux's flush_unauthorized_files */
 684 void aa_inherit_files(const struct cred *cred, struct files_struct *files)
 685 {
 686         struct aa_label *label = aa_get_newest_cred_label(cred);
 687         struct file *devnull = NULL;
 688         unsigned n;
 689
 690         revalidate_tty(label);
 691
 692         /* Revalidate access to inherited open files. */
 693         n = iterate_fd(files, 0, match_file, label);
 694         if (!n) /* none found? */
 695                 goto out;
 696
 697         devnull = dentry_open(&aa_null, O_RDWR, cred);
 698         if (IS_ERR(devnull))
 699                 devnull = NULL;
 700         /* replace all the matching ones with this */
 701         do {
 702                 replace_fd(n - 1, devnull, 0);
 703         } while ((n = iterate_fd(files, n, match_file, label)) != 0);
 704         if (devnull)
 705                 fput(devnull);
 706 out:
 707         aa_put_label(label);
 708 }