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