1 // SPDX-License-Identifier: GPL-2.0-or-later 2 /* 3 * Copyright (C) 2008 Red Hat, Inc., Eric Paris <eparis@redhat.com> 4 */ 5 6 #include <linux/dcache.h> 7 #include <linux/fs.h> 8 #include <linux/gfp.h> 9 #include <linux/init.h> 10 #include <linux/module.h> 11 #include <linux/mount.h> 12 #include <linux/srcu.h> 13 14 #include <linux/fsnotify_backend.h> 15 #include "fsnotify.h" 16 17 /* 18 * Clear all of the marks on an inode when it is being evicted from core 19 */ 20 void __fsnotify_inode_delete(struct inode *inode) 21 { 22 fsnotify_clear_marks_by_inode(inode); 23 } 24 EXPORT_SYMBOL_GPL(__fsnotify_inode_delete); 25 26 void __fsnotify_vfsmount_delete(struct vfsmount *mnt) 27 { 28 fsnotify_clear_marks_by_mount(mnt); 29 } 30 31 /** 32 * fsnotify_unmount_inodes - an sb is unmounting. handle any watched inodes. 33 * @sb: superblock being unmounted. 34 * 35 * Called during unmount with no locks held, so needs to be safe against 36 * concurrent modifiers. We temporarily drop sb->s_inode_list_lock and CAN block. 37 */ 38 static void fsnotify_unmount_inodes(struct super_block *sb) 39 { 40 struct inode *inode, *iput_inode = NULL; 41 42 spin_lock(&sb->s_inode_list_lock); 43 list_for_each_entry(inode, &sb->s_inodes, i_sb_list) { 44 /* 45 * We cannot __iget() an inode in state I_FREEING, 46 * I_WILL_FREE, or I_NEW which is fine because by that point 47 * the inode cannot have any associated watches. 48 */ 49 spin_lock(&inode->i_lock); 50 if (inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW)) { 51 spin_unlock(&inode->i_lock); 52 continue; 53 } 54 55 /* 56 * If i_count is zero, the inode cannot have any watches and 57 * doing an __iget/iput with SB_ACTIVE clear would actually 58 * evict all inodes with zero i_count from icache which is 59 * unnecessarily violent and may in fact be illegal to do. 60 * However, we should have been called /after/ evict_inodes 61 * removed all zero refcount inodes, in any case. Test to 62 * be sure. 63 */ 64 if (!atomic_read(&inode->i_count)) { 65 spin_unlock(&inode->i_lock); 66 continue; 67 } 68 69 __iget(inode); 70 spin_unlock(&inode->i_lock); 71 spin_unlock(&sb->s_inode_list_lock); 72 73 iput(iput_inode); 74 75 /* for each watch, send FS_UNMOUNT and then remove it */ 76 fsnotify_inode(inode, FS_UNMOUNT); 77 78 fsnotify_inode_delete(inode); 79 80 iput_inode = inode; 81 82 cond_resched(); 83 spin_lock(&sb->s_inode_list_lock); 84 } 85 spin_unlock(&sb->s_inode_list_lock); 86 87 iput(iput_inode); 88 } 89 90 void fsnotify_sb_delete(struct super_block *sb) 91 { 92 fsnotify_unmount_inodes(sb); 93 fsnotify_clear_marks_by_sb(sb); 94 /* Wait for outstanding object references from connectors */ 95 wait_var_event(&sb->s_fsnotify_connectors, 96 !atomic_long_read(&sb->s_fsnotify_connectors)); 97 } 98 99 /* 100 * Given an inode, first check if we care what happens to our children. Inotify 101 * and dnotify both tell their parents about events. If we care about any event 102 * on a child we run all of our children and set a dentry flag saying that the 103 * parent cares. Thus when an event happens on a child it can quickly tell if 104 * if there is a need to find a parent and send the event to the parent. 105 */ 106 void __fsnotify_update_child_dentry_flags(struct inode *inode) 107 { 108 struct dentry *alias; 109 int watched; 110 111 if (!S_ISDIR(inode->i_mode)) 112 return; 113 114 /* determine if the children should tell inode about their events */ 115 watched = fsnotify_inode_watches_children(inode); 116 117 spin_lock(&inode->i_lock); 118 /* run all of the dentries associated with this inode. Since this is a 119 * directory, there damn well better only be one item on this list */ 120 hlist_for_each_entry(alias, &inode->i_dentry, d_u.d_alias) { 121 struct dentry *child; 122 123 /* run all of the children of the original inode and fix their 124 * d_flags to indicate parental interest (their parent is the 125 * original inode) */ 126 spin_lock(&alias->d_lock); 127 list_for_each_entry(child, &alias->d_subdirs, d_child) { 128 if (!child->d_inode) 129 continue; 130 131 spin_lock_nested(&child->d_lock, DENTRY_D_LOCK_NESTED); 132 if (watched) 133 child->d_flags |= DCACHE_FSNOTIFY_PARENT_WATCHED; 134 else 135 child->d_flags &= ~DCACHE_FSNOTIFY_PARENT_WATCHED; 136 spin_unlock(&child->d_lock); 137 } 138 spin_unlock(&alias->d_lock); 139 } 140 spin_unlock(&inode->i_lock); 141 } 142 143 /* Are inode/sb/mount interested in parent and name info with this event? */ 144 static bool fsnotify_event_needs_parent(struct inode *inode, struct mount *mnt, 145 __u32 mask) 146 { 147 __u32 marks_mask = 0; 148 149 /* We only send parent/name to inode/sb/mount for events on non-dir */ 150 if (mask & FS_ISDIR) 151 return false; 152 153 /* 154 * All events that are possible on child can also may be reported with 155 * parent/name info to inode/sb/mount. Otherwise, a watching parent 156 * could result in events reported with unexpected name info to sb/mount. 157 */ 158 BUILD_BUG_ON(FS_EVENTS_POSS_ON_CHILD & ~FS_EVENTS_POSS_TO_PARENT); 159 160 /* Did either inode/sb/mount subscribe for events with parent/name? */ 161 marks_mask |= fsnotify_parent_needed_mask(inode->i_fsnotify_mask); 162 marks_mask |= fsnotify_parent_needed_mask(inode->i_sb->s_fsnotify_mask); 163 if (mnt) 164 marks_mask |= fsnotify_parent_needed_mask(mnt->mnt_fsnotify_mask); 165 166 /* Did they subscribe for this event with parent/name info? */ 167 return mask & marks_mask; 168 } 169 170 /* 171 * Notify this dentry's parent about a child's events with child name info 172 * if parent is watching or if inode/sb/mount are interested in events with 173 * parent and name info. 174 * 175 * Notify only the child without name info if parent is not watching and 176 * inode/sb/mount are not interested in events with parent and name info. 177 */ 178 int __fsnotify_parent(struct dentry *dentry, __u32 mask, const void *data, 179 int data_type) 180 { 181 const struct path *path = fsnotify_data_path(data, data_type); 182 struct mount *mnt = path ? real_mount(path->mnt) : NULL; 183 struct inode *inode = d_inode(dentry); 184 struct dentry *parent; 185 bool parent_watched = dentry->d_flags & DCACHE_FSNOTIFY_PARENT_WATCHED; 186 bool parent_needed, parent_interested; 187 __u32 p_mask; 188 struct inode *p_inode = NULL; 189 struct name_snapshot name; 190 struct qstr *file_name = NULL; 191 int ret = 0; 192 193 /* 194 * Do inode/sb/mount care about parent and name info on non-dir? 195 * Do they care about any event at all? 196 */ 197 if (!inode->i_fsnotify_marks && !inode->i_sb->s_fsnotify_marks && 198 (!mnt || !mnt->mnt_fsnotify_marks) && !parent_watched) 199 return 0; 200 201 parent = NULL; 202 parent_needed = fsnotify_event_needs_parent(inode, mnt, mask); 203 if (!parent_watched && !parent_needed) 204 goto notify; 205 206 /* Does parent inode care about events on children? */ 207 parent = dget_parent(dentry); 208 p_inode = parent->d_inode; 209 p_mask = fsnotify_inode_watches_children(p_inode); 210 if (unlikely(parent_watched && !p_mask)) 211 __fsnotify_update_child_dentry_flags(p_inode); 212 213 /* 214 * Include parent/name in notification either if some notification 215 * groups require parent info or the parent is interested in this event. 216 */ 217 parent_interested = mask & p_mask & ALL_FSNOTIFY_EVENTS; 218 if (parent_needed || parent_interested) { 219 /* When notifying parent, child should be passed as data */ 220 WARN_ON_ONCE(inode != fsnotify_data_inode(data, data_type)); 221 222 /* Notify both parent and child with child name info */ 223 take_dentry_name_snapshot(&name, dentry); 224 file_name = &name.name; 225 if (parent_interested) 226 mask |= FS_EVENT_ON_CHILD; 227 } 228 229 notify: 230 ret = fsnotify(mask, data, data_type, p_inode, file_name, inode, 0); 231 232 if (file_name) 233 release_dentry_name_snapshot(&name); 234 dput(parent); 235 236 return ret; 237 } 238 EXPORT_SYMBOL_GPL(__fsnotify_parent); 239 240 static int fsnotify_handle_inode_event(struct fsnotify_group *group, 241 struct fsnotify_mark *inode_mark, 242 u32 mask, const void *data, int data_type, 243 struct inode *dir, const struct qstr *name, 244 u32 cookie) 245 { 246 const struct path *path = fsnotify_data_path(data, data_type); 247 struct inode *inode = fsnotify_data_inode(data, data_type); 248 const struct fsnotify_ops *ops = group->ops; 249 250 if (WARN_ON_ONCE(!ops->handle_inode_event)) 251 return 0; 252 253 if (WARN_ON_ONCE(!inode && !dir)) 254 return 0; 255 256 if ((inode_mark->flags & FSNOTIFY_MARK_FLAG_EXCL_UNLINK) && 257 path && d_unlinked(path->dentry)) 258 return 0; 259 260 /* Check interest of this mark in case event was sent with two marks */ 261 if (!(mask & inode_mark->mask & ALL_FSNOTIFY_EVENTS)) 262 return 0; 263 264 return ops->handle_inode_event(inode_mark, mask, inode, dir, name, cookie); 265 } 266 267 static int fsnotify_handle_event(struct fsnotify_group *group, __u32 mask, 268 const void *data, int data_type, 269 struct inode *dir, const struct qstr *name, 270 u32 cookie, struct fsnotify_iter_info *iter_info) 271 { 272 struct fsnotify_mark *inode_mark = fsnotify_iter_inode_mark(iter_info); 273 struct fsnotify_mark *parent_mark = fsnotify_iter_parent_mark(iter_info); 274 int ret; 275 276 if (WARN_ON_ONCE(fsnotify_iter_sb_mark(iter_info)) || 277 WARN_ON_ONCE(fsnotify_iter_vfsmount_mark(iter_info))) 278 return 0; 279 280 /* 281 * For FS_RENAME, 'dir' is old dir and 'data' is new dentry. 282 * The only ->handle_inode_event() backend that supports FS_RENAME is 283 * dnotify, where it means file was renamed within same parent. 284 */ 285 if (mask & FS_RENAME) { 286 struct dentry *moved = fsnotify_data_dentry(data, data_type); 287 288 if (dir != moved->d_parent->d_inode) 289 return 0; 290 } 291 292 if (parent_mark) { 293 ret = fsnotify_handle_inode_event(group, parent_mark, mask, 294 data, data_type, dir, name, 0); 295 if (ret) 296 return ret; 297 } 298 299 if (!inode_mark) 300 return 0; 301 302 if (mask & FS_EVENT_ON_CHILD) { 303 /* 304 * Some events can be sent on both parent dir and child marks 305 * (e.g. FS_ATTRIB). If both parent dir and child are 306 * watching, report the event once to parent dir with name (if 307 * interested) and once to child without name (if interested). 308 * The child watcher is expecting an event without a file name 309 * and without the FS_EVENT_ON_CHILD flag. 310 */ 311 mask &= ~FS_EVENT_ON_CHILD; 312 dir = NULL; 313 name = NULL; 314 } 315 316 return fsnotify_handle_inode_event(group, inode_mark, mask, data, data_type, 317 dir, name, cookie); 318 } 319 320 static int send_to_group(__u32 mask, const void *data, int data_type, 321 struct inode *dir, const struct qstr *file_name, 322 u32 cookie, struct fsnotify_iter_info *iter_info) 323 { 324 struct fsnotify_group *group = NULL; 325 __u32 test_mask = (mask & ALL_FSNOTIFY_EVENTS); 326 __u32 marks_mask = 0; 327 __u32 marks_ignored_mask = 0; 328 struct fsnotify_mark *mark; 329 int type; 330 331 if (!iter_info->report_mask) 332 return 0; 333 334 /* clear ignored on inode modification */ 335 if (mask & FS_MODIFY) { 336 fsnotify_foreach_iter_mark_type(iter_info, mark, type) { 337 if (!(mark->flags & 338 FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY)) 339 mark->ignored_mask = 0; 340 } 341 } 342 343 /* Are any of the group marks interested in this event? */ 344 fsnotify_foreach_iter_mark_type(iter_info, mark, type) { 345 group = mark->group; 346 marks_mask |= mark->mask; 347 marks_ignored_mask |= mark->ignored_mask; 348 } 349 350 pr_debug("%s: group=%p mask=%x marks_mask=%x marks_ignored_mask=%x data=%p data_type=%d dir=%p cookie=%d\n", 351 __func__, group, mask, marks_mask, marks_ignored_mask, 352 data, data_type, dir, cookie); 353 354 if (!(test_mask & marks_mask & ~marks_ignored_mask)) 355 return 0; 356 357 if (group->ops->handle_event) { 358 return group->ops->handle_event(group, mask, data, data_type, dir, 359 file_name, cookie, iter_info); 360 } 361 362 return fsnotify_handle_event(group, mask, data, data_type, dir, 363 file_name, cookie, iter_info); 364 } 365 366 static struct fsnotify_mark *fsnotify_first_mark(struct fsnotify_mark_connector **connp) 367 { 368 struct fsnotify_mark_connector *conn; 369 struct hlist_node *node = NULL; 370 371 conn = srcu_dereference(*connp, &fsnotify_mark_srcu); 372 if (conn) 373 node = srcu_dereference(conn->list.first, &fsnotify_mark_srcu); 374 375 return hlist_entry_safe(node, struct fsnotify_mark, obj_list); 376 } 377 378 static struct fsnotify_mark *fsnotify_next_mark(struct fsnotify_mark *mark) 379 { 380 struct hlist_node *node = NULL; 381 382 if (mark) 383 node = srcu_dereference(mark->obj_list.next, 384 &fsnotify_mark_srcu); 385 386 return hlist_entry_safe(node, struct fsnotify_mark, obj_list); 387 } 388 389 /* 390 * iter_info is a multi head priority queue of marks. 391 * Pick a subset of marks from queue heads, all with the same group 392 * and set the report_mask to a subset of the selected marks. 393 * Returns false if there are no more groups to iterate. 394 */ 395 static bool fsnotify_iter_select_report_types( 396 struct fsnotify_iter_info *iter_info) 397 { 398 struct fsnotify_group *max_prio_group = NULL; 399 struct fsnotify_mark *mark; 400 int type; 401 402 /* Choose max prio group among groups of all queue heads */ 403 fsnotify_foreach_iter_type(type) { 404 mark = iter_info->marks[type]; 405 if (mark && 406 fsnotify_compare_groups(max_prio_group, mark->group) > 0) 407 max_prio_group = mark->group; 408 } 409 410 if (!max_prio_group) 411 return false; 412 413 /* Set the report mask for marks from same group as max prio group */ 414 iter_info->current_group = max_prio_group; 415 iter_info->report_mask = 0; 416 fsnotify_foreach_iter_type(type) { 417 mark = iter_info->marks[type]; 418 if (mark && mark->group == iter_info->current_group) { 419 /* 420 * FSNOTIFY_ITER_TYPE_PARENT indicates that this inode 421 * is watching children and interested in this event, 422 * which is an event possible on child. 423 * But is *this mark* watching children? 424 */ 425 if (type == FSNOTIFY_ITER_TYPE_PARENT && 426 !(mark->mask & FS_EVENT_ON_CHILD)) 427 continue; 428 429 fsnotify_iter_set_report_type(iter_info, type); 430 } 431 } 432 433 return true; 434 } 435 436 /* 437 * Pop from iter_info multi head queue, the marks that belong to the group of 438 * current iteration step. 439 */ 440 static void fsnotify_iter_next(struct fsnotify_iter_info *iter_info) 441 { 442 struct fsnotify_mark *mark; 443 int type; 444 445 /* 446 * We cannot use fsnotify_foreach_iter_mark_type() here because we 447 * may need to advance a mark of type X that belongs to current_group 448 * but was not selected for reporting. 449 */ 450 fsnotify_foreach_iter_type(type) { 451 mark = iter_info->marks[type]; 452 if (mark && mark->group == iter_info->current_group) 453 iter_info->marks[type] = 454 fsnotify_next_mark(iter_info->marks[type]); 455 } 456 } 457 458 /* 459 * fsnotify - This is the main call to fsnotify. 460 * 461 * The VFS calls into hook specific functions in linux/fsnotify.h. 462 * Those functions then in turn call here. Here will call out to all of the 463 * registered fsnotify_group. Those groups can then use the notification event 464 * in whatever means they feel necessary. 465 * 466 * @mask: event type and flags 467 * @data: object that event happened on 468 * @data_type: type of object for fanotify_data_XXX() accessors 469 * @dir: optional directory associated with event - 470 * if @file_name is not NULL, this is the directory that 471 * @file_name is relative to 472 * @file_name: optional file name associated with event 473 * @inode: optional inode associated with event - 474 * If @dir and @inode are both non-NULL, event may be 475 * reported to both. 476 * @cookie: inotify rename cookie 477 */ 478 int fsnotify(__u32 mask, const void *data, int data_type, struct inode *dir, 479 const struct qstr *file_name, struct inode *inode, u32 cookie) 480 { 481 const struct path *path = fsnotify_data_path(data, data_type); 482 struct super_block *sb = fsnotify_data_sb(data, data_type); 483 struct fsnotify_iter_info iter_info = {}; 484 struct mount *mnt = NULL; 485 struct inode *inode2 = NULL; 486 struct dentry *moved; 487 int inode2_type; 488 int ret = 0; 489 __u32 test_mask, marks_mask; 490 491 if (path) 492 mnt = real_mount(path->mnt); 493 494 if (!inode) { 495 /* Dirent event - report on TYPE_INODE to dir */ 496 inode = dir; 497 /* For FS_RENAME, inode is old_dir and inode2 is new_dir */ 498 if (mask & FS_RENAME) { 499 moved = fsnotify_data_dentry(data, data_type); 500 inode2 = moved->d_parent->d_inode; 501 inode2_type = FSNOTIFY_ITER_TYPE_INODE2; 502 } 503 } else if (mask & FS_EVENT_ON_CHILD) { 504 /* 505 * Event on child - report on TYPE_PARENT to dir if it is 506 * watching children and on TYPE_INODE to child. 507 */ 508 inode2 = dir; 509 inode2_type = FSNOTIFY_ITER_TYPE_PARENT; 510 } 511 512 /* 513 * Optimization: srcu_read_lock() has a memory barrier which can 514 * be expensive. It protects walking the *_fsnotify_marks lists. 515 * However, if we do not walk the lists, we do not have to do 516 * SRCU because we have no references to any objects and do not 517 * need SRCU to keep them "alive". 518 */ 519 if (!sb->s_fsnotify_marks && 520 (!mnt || !mnt->mnt_fsnotify_marks) && 521 (!inode || !inode->i_fsnotify_marks) && 522 (!inode2 || !inode2->i_fsnotify_marks)) 523 return 0; 524 525 marks_mask = sb->s_fsnotify_mask; 526 if (mnt) 527 marks_mask |= mnt->mnt_fsnotify_mask; 528 if (inode) 529 marks_mask |= inode->i_fsnotify_mask; 530 if (inode2) 531 marks_mask |= inode2->i_fsnotify_mask; 532 533 534 /* 535 * If this is a modify event we may need to clear some ignored masks. 536 * In that case, the object with ignored masks will have the FS_MODIFY 537 * event in its mask. 538 * Otherwise, return if none of the marks care about this type of event. 539 */ 540 test_mask = (mask & ALL_FSNOTIFY_EVENTS); 541 if (!(test_mask & marks_mask)) 542 return 0; 543 544 iter_info.srcu_idx = srcu_read_lock(&fsnotify_mark_srcu); 545 546 iter_info.marks[FSNOTIFY_ITER_TYPE_SB] = 547 fsnotify_first_mark(&sb->s_fsnotify_marks); 548 if (mnt) { 549 iter_info.marks[FSNOTIFY_ITER_TYPE_VFSMOUNT] = 550 fsnotify_first_mark(&mnt->mnt_fsnotify_marks); 551 } 552 if (inode) { 553 iter_info.marks[FSNOTIFY_ITER_TYPE_INODE] = 554 fsnotify_first_mark(&inode->i_fsnotify_marks); 555 } 556 if (inode2) { 557 iter_info.marks[inode2_type] = 558 fsnotify_first_mark(&inode2->i_fsnotify_marks); 559 } 560 561 /* 562 * We need to merge inode/vfsmount/sb mark lists so that e.g. inode mark 563 * ignore masks are properly reflected for mount/sb mark notifications. 564 * That's why this traversal is so complicated... 565 */ 566 while (fsnotify_iter_select_report_types(&iter_info)) { 567 ret = send_to_group(mask, data, data_type, dir, file_name, 568 cookie, &iter_info); 569 570 if (ret && (mask & ALL_FSNOTIFY_PERM_EVENTS)) 571 goto out; 572 573 fsnotify_iter_next(&iter_info); 574 } 575 ret = 0; 576 out: 577 srcu_read_unlock(&fsnotify_mark_srcu, iter_info.srcu_idx); 578 579 return ret; 580 } 581 EXPORT_SYMBOL_GPL(fsnotify); 582 583 static __init int fsnotify_init(void) 584 { 585 int ret; 586 587 BUILD_BUG_ON(HWEIGHT32(ALL_FSNOTIFY_BITS) != 23); 588 589 ret = init_srcu_struct(&fsnotify_mark_srcu); 590 if (ret) 591 panic("initializing fsnotify_mark_srcu"); 592 593 fsnotify_mark_connector_cachep = KMEM_CACHE(fsnotify_mark_connector, 594 SLAB_PANIC); 595 596 return 0; 597 } 598 core_initcall(fsnotify_init); 599