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 */ 20void __fsnotify_inode_delete(struct inode *inode) 21{ 22 fsnotify_clear_marks_by_inode(inode); 23} 24EXPORT_SYMBOL_GPL(__fsnotify_inode_delete); 25 26void __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 */ 38static 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 90void 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 104 * if there is a need to find a parent and send the event to the parent. 105 */ 106void __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 hlist_for_each_entry(child, &alias->d_children, d_sib) { 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? */ 144static bool fsnotify_event_needs_parent(struct inode *inode, __u32 mnt_mask, 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 marks_mask |= fsnotify_parent_needed_mask(mnt_mask); 164 165 /* Did they subscribe for this event with parent/name info? */ 166 return mask & marks_mask; 167} 168 169/* Are there any inode/mount/sb objects that are interested in this event? */ 170static inline bool fsnotify_object_watched(struct inode *inode, __u32 mnt_mask, 171 __u32 mask) 172{ 173 __u32 marks_mask = inode->i_fsnotify_mask | mnt_mask | 174 inode->i_sb->s_fsnotify_mask; 175 176 return mask & marks_mask & ALL_FSNOTIFY_EVENTS; 177} 178 179/* 180 * Notify this dentry's parent about a child's events with child name info 181 * if parent is watching or if inode/sb/mount are interested in events with 182 * parent and name info. 183 * 184 * Notify only the child without name info if parent is not watching and 185 * inode/sb/mount are not interested in events with parent and name info. 186 */ 187int __fsnotify_parent(struct dentry *dentry, __u32 mask, const void *data, 188 int data_type) 189{ 190 const struct path *path = fsnotify_data_path(data, data_type); 191 __u32 mnt_mask = path ? real_mount(path->mnt)->mnt_fsnotify_mask : 0; 192 struct inode *inode = d_inode(dentry); 193 struct dentry *parent; 194 bool parent_watched = dentry->d_flags & DCACHE_FSNOTIFY_PARENT_WATCHED; 195 bool parent_needed, parent_interested; 196 __u32 p_mask; 197 struct inode *p_inode = NULL; 198 struct name_snapshot name; 199 struct qstr *file_name = NULL; 200 int ret = 0; 201 202 /* Optimize the likely case of nobody watching this path */ 203 if (likely(!parent_watched && 204 !fsnotify_object_watched(inode, mnt_mask, mask))) 205 return 0; 206 207 parent = NULL; 208 parent_needed = fsnotify_event_needs_parent(inode, mnt_mask, mask); 209 if (!parent_watched && !parent_needed) 210 goto notify; 211 212 /* Does parent inode care about events on children? */ 213 parent = dget_parent(dentry); 214 p_inode = parent->d_inode; 215 p_mask = fsnotify_inode_watches_children(p_inode); 216 if (unlikely(parent_watched && !p_mask)) 217 __fsnotify_update_child_dentry_flags(p_inode); 218 219 /* 220 * Include parent/name in notification either if some notification 221 * groups require parent info or the parent is interested in this event. 222 */ 223 parent_interested = mask & p_mask & ALL_FSNOTIFY_EVENTS; 224 if (parent_needed || parent_interested) { 225 /* When notifying parent, child should be passed as data */ 226 WARN_ON_ONCE(inode != fsnotify_data_inode(data, data_type)); 227 228 /* Notify both parent and child with child name info */ 229 take_dentry_name_snapshot(&name, dentry); 230 file_name = &name.name; 231 if (parent_interested) 232 mask |= FS_EVENT_ON_CHILD; 233 } 234 235notify: 236 ret = fsnotify(mask, data, data_type, p_inode, file_name, inode, 0); 237 238 if (file_name) 239 release_dentry_name_snapshot(&name); 240 dput(parent); 241 242 return ret; 243} 244EXPORT_SYMBOL_GPL(__fsnotify_parent); 245 246static int fsnotify_handle_inode_event(struct fsnotify_group *group, 247 struct fsnotify_mark *inode_mark, 248 u32 mask, const void *data, int data_type, 249 struct inode *dir, const struct qstr *name, 250 u32 cookie) 251{ 252 const struct path *path = fsnotify_data_path(data, data_type); 253 struct inode *inode = fsnotify_data_inode(data, data_type); 254 const struct fsnotify_ops *ops = group->ops; 255 256 if (WARN_ON_ONCE(!ops->handle_inode_event)) 257 return 0; 258 259 if (WARN_ON_ONCE(!inode && !dir)) 260 return 0; 261 262 if ((inode_mark->flags & FSNOTIFY_MARK_FLAG_EXCL_UNLINK) && 263 path && d_unlinked(path->dentry)) 264 return 0; 265 266 /* Check interest of this mark in case event was sent with two marks */ 267 if (!(mask & inode_mark->mask & ALL_FSNOTIFY_EVENTS)) 268 return 0; 269 270 return ops->handle_inode_event(inode_mark, mask, inode, dir, name, cookie); 271} 272 273static int fsnotify_handle_event(struct fsnotify_group *group, __u32 mask, 274 const void *data, int data_type, 275 struct inode *dir, const struct qstr *name, 276 u32 cookie, struct fsnotify_iter_info *iter_info) 277{ 278 struct fsnotify_mark *inode_mark = fsnotify_iter_inode_mark(iter_info); 279 struct fsnotify_mark *parent_mark = fsnotify_iter_parent_mark(iter_info); 280 int ret; 281 282 if (WARN_ON_ONCE(fsnotify_iter_sb_mark(iter_info)) || 283 WARN_ON_ONCE(fsnotify_iter_vfsmount_mark(iter_info))) 284 return 0; 285 286 /* 287 * For FS_RENAME, 'dir' is old dir and 'data' is new dentry. 288 * The only ->handle_inode_event() backend that supports FS_RENAME is 289 * dnotify, where it means file was renamed within same parent. 290 */ 291 if (mask & FS_RENAME) { 292 struct dentry *moved = fsnotify_data_dentry(data, data_type); 293 294 if (dir != moved->d_parent->d_inode) 295 return 0; 296 } 297 298 if (parent_mark) { 299 ret = fsnotify_handle_inode_event(group, parent_mark, mask, 300 data, data_type, dir, name, 0); 301 if (ret) 302 return ret; 303 } 304 305 if (!inode_mark) 306 return 0; 307 308 if (mask & FS_EVENT_ON_CHILD) { 309 /* 310 * Some events can be sent on both parent dir and child marks 311 * (e.g. FS_ATTRIB). If both parent dir and child are 312 * watching, report the event once to parent dir with name (if 313 * interested) and once to child without name (if interested). 314 * The child watcher is expecting an event without a file name 315 * and without the FS_EVENT_ON_CHILD flag. 316 */ 317 mask &= ~FS_EVENT_ON_CHILD; 318 dir = NULL; 319 name = NULL; 320 } 321 322 return fsnotify_handle_inode_event(group, inode_mark, mask, data, data_type, 323 dir, name, cookie); 324} 325 326static int send_to_group(__u32 mask, const void *data, int data_type, 327 struct inode *dir, const struct qstr *file_name, 328 u32 cookie, struct fsnotify_iter_info *iter_info) 329{ 330 struct fsnotify_group *group = NULL; 331 __u32 test_mask = (mask & ALL_FSNOTIFY_EVENTS); 332 __u32 marks_mask = 0; 333 __u32 marks_ignore_mask = 0; 334 bool is_dir = mask & FS_ISDIR; 335 struct fsnotify_mark *mark; 336 int type; 337 338 if (!iter_info->report_mask) 339 return 0; 340 341 /* clear ignored on inode modification */ 342 if (mask & FS_MODIFY) { 343 fsnotify_foreach_iter_mark_type(iter_info, mark, type) { 344 if (!(mark->flags & 345 FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY)) 346 mark->ignore_mask = 0; 347 } 348 } 349 350 /* Are any of the group marks interested in this event? */ 351 fsnotify_foreach_iter_mark_type(iter_info, mark, type) { 352 group = mark->group; 353 marks_mask |= mark->mask; 354 marks_ignore_mask |= 355 fsnotify_effective_ignore_mask(mark, is_dir, type); 356 } 357 358 pr_debug("%s: group=%p mask=%x marks_mask=%x marks_ignore_mask=%x data=%p data_type=%d dir=%p cookie=%d\n", 359 __func__, group, mask, marks_mask, marks_ignore_mask, 360 data, data_type, dir, cookie); 361 362 if (!(test_mask & marks_mask & ~marks_ignore_mask)) 363 return 0; 364 365 if (group->ops->handle_event) { 366 return group->ops->handle_event(group, mask, data, data_type, dir, 367 file_name, cookie, iter_info); 368 } 369 370 return fsnotify_handle_event(group, mask, data, data_type, dir, 371 file_name, cookie, iter_info); 372} 373 374static struct fsnotify_mark *fsnotify_first_mark(struct fsnotify_mark_connector **connp) 375{ 376 struct fsnotify_mark_connector *conn; 377 struct hlist_node *node = NULL; 378 379 conn = srcu_dereference(*connp, &fsnotify_mark_srcu); 380 if (conn) 381 node = srcu_dereference(conn->list.first, &fsnotify_mark_srcu); 382 383 return hlist_entry_safe(node, struct fsnotify_mark, obj_list); 384} 385 386static struct fsnotify_mark *fsnotify_next_mark(struct fsnotify_mark *mark) 387{ 388 struct hlist_node *node = NULL; 389 390 if (mark) 391 node = srcu_dereference(mark->obj_list.next, 392 &fsnotify_mark_srcu); 393 394 return hlist_entry_safe(node, struct fsnotify_mark, obj_list); 395} 396 397/* 398 * iter_info is a multi head priority queue of marks. 399 * Pick a subset of marks from queue heads, all with the same group 400 * and set the report_mask to a subset of the selected marks. 401 * Returns false if there are no more groups to iterate. 402 */ 403static bool fsnotify_iter_select_report_types( 404 struct fsnotify_iter_info *iter_info) 405{ 406 struct fsnotify_group *max_prio_group = NULL; 407 struct fsnotify_mark *mark; 408 int type; 409 410 /* Choose max prio group among groups of all queue heads */ 411 fsnotify_foreach_iter_type(type) { 412 mark = iter_info->marks[type]; 413 if (mark && 414 fsnotify_compare_groups(max_prio_group, mark->group) > 0) 415 max_prio_group = mark->group; 416 } 417 418 if (!max_prio_group) 419 return false; 420 421 /* Set the report mask for marks from same group as max prio group */ 422 iter_info->current_group = max_prio_group; 423 iter_info->report_mask = 0; 424 fsnotify_foreach_iter_type(type) { 425 mark = iter_info->marks[type]; 426 if (mark && mark->group == iter_info->current_group) { 427 /* 428 * FSNOTIFY_ITER_TYPE_PARENT indicates that this inode 429 * is watching children and interested in this event, 430 * which is an event possible on child. 431 * But is *this mark* watching children? 432 */ 433 if (type == FSNOTIFY_ITER_TYPE_PARENT && 434 !(mark->mask & FS_EVENT_ON_CHILD) && 435 !(fsnotify_ignore_mask(mark) & FS_EVENT_ON_CHILD)) 436 continue; 437 438 fsnotify_iter_set_report_type(iter_info, type); 439 } 440 } 441 442 return true; 443} 444 445/* 446 * Pop from iter_info multi head queue, the marks that belong to the group of 447 * current iteration step. 448 */ 449static void fsnotify_iter_next(struct fsnotify_iter_info *iter_info) 450{ 451 struct fsnotify_mark *mark; 452 int type; 453 454 /* 455 * We cannot use fsnotify_foreach_iter_mark_type() here because we 456 * may need to advance a mark of type X that belongs to current_group 457 * but was not selected for reporting. 458 */ 459 fsnotify_foreach_iter_type(type) { 460 mark = iter_info->marks[type]; 461 if (mark && mark->group == iter_info->current_group) 462 iter_info->marks[type] = 463 fsnotify_next_mark(iter_info->marks[type]); 464 } 465} 466 467/* 468 * fsnotify - This is the main call to fsnotify. 469 * 470 * The VFS calls into hook specific functions in linux/fsnotify.h. 471 * Those functions then in turn call here. Here will call out to all of the 472 * registered fsnotify_group. Those groups can then use the notification event 473 * in whatever means they feel necessary. 474 * 475 * @mask: event type and flags 476 * @data: object that event happened on 477 * @data_type: type of object for fanotify_data_XXX() accessors 478 * @dir: optional directory associated with event - 479 * if @file_name is not NULL, this is the directory that 480 * @file_name is relative to 481 * @file_name: optional file name associated with event 482 * @inode: optional inode associated with event - 483 * If @dir and @inode are both non-NULL, event may be 484 * reported to both. 485 * @cookie: inotify rename cookie 486 */ 487int fsnotify(__u32 mask, const void *data, int data_type, struct inode *dir, 488 const struct qstr *file_name, struct inode *inode, u32 cookie) 489{ 490 const struct path *path = fsnotify_data_path(data, data_type); 491 struct super_block *sb = fsnotify_data_sb(data, data_type); 492 struct fsnotify_iter_info iter_info = {}; 493 struct mount *mnt = NULL; 494 struct inode *inode2 = NULL; 495 struct dentry *moved; 496 int inode2_type; 497 int ret = 0; 498 __u32 test_mask, marks_mask; 499 500 if (path) 501 mnt = real_mount(path->mnt); 502 503 if (!inode) { 504 /* Dirent event - report on TYPE_INODE to dir */ 505 inode = dir; 506 /* For FS_RENAME, inode is old_dir and inode2 is new_dir */ 507 if (mask & FS_RENAME) { 508 moved = fsnotify_data_dentry(data, data_type); 509 inode2 = moved->d_parent->d_inode; 510 inode2_type = FSNOTIFY_ITER_TYPE_INODE2; 511 } 512 } else if (mask & FS_EVENT_ON_CHILD) { 513 /* 514 * Event on child - report on TYPE_PARENT to dir if it is 515 * watching children and on TYPE_INODE to child. 516 */ 517 inode2 = dir; 518 inode2_type = FSNOTIFY_ITER_TYPE_PARENT; 519 } 520 521 /* 522 * Optimization: srcu_read_lock() has a memory barrier which can 523 * be expensive. It protects walking the *_fsnotify_marks lists. 524 * However, if we do not walk the lists, we do not have to do 525 * SRCU because we have no references to any objects and do not 526 * need SRCU to keep them "alive". 527 */ 528 if (!sb->s_fsnotify_marks && 529 (!mnt || !mnt->mnt_fsnotify_marks) && 530 (!inode || !inode->i_fsnotify_marks) && 531 (!inode2 || !inode2->i_fsnotify_marks)) 532 return 0; 533 534 marks_mask = sb->s_fsnotify_mask; 535 if (mnt) 536 marks_mask |= mnt->mnt_fsnotify_mask; 537 if (inode) 538 marks_mask |= inode->i_fsnotify_mask; 539 if (inode2) 540 marks_mask |= inode2->i_fsnotify_mask; 541 542 543 /* 544 * If this is a modify event we may need to clear some ignore masks. 545 * In that case, the object with ignore masks will have the FS_MODIFY 546 * event in its mask. 547 * Otherwise, return if none of the marks care about this type of event. 548 */ 549 test_mask = (mask & ALL_FSNOTIFY_EVENTS); 550 if (!(test_mask & marks_mask)) 551 return 0; 552 553 iter_info.srcu_idx = srcu_read_lock(&fsnotify_mark_srcu); 554 555 iter_info.marks[FSNOTIFY_ITER_TYPE_SB] = 556 fsnotify_first_mark(&sb->s_fsnotify_marks); 557 if (mnt) { 558 iter_info.marks[FSNOTIFY_ITER_TYPE_VFSMOUNT] = 559 fsnotify_first_mark(&mnt->mnt_fsnotify_marks); 560 } 561 if (inode) { 562 iter_info.marks[FSNOTIFY_ITER_TYPE_INODE] = 563 fsnotify_first_mark(&inode->i_fsnotify_marks); 564 } 565 if (inode2) { 566 iter_info.marks[inode2_type] = 567 fsnotify_first_mark(&inode2->i_fsnotify_marks); 568 } 569 570 /* 571 * We need to merge inode/vfsmount/sb mark lists so that e.g. inode mark 572 * ignore masks are properly reflected for mount/sb mark notifications. 573 * That's why this traversal is so complicated... 574 */ 575 while (fsnotify_iter_select_report_types(&iter_info)) { 576 ret = send_to_group(mask, data, data_type, dir, file_name, 577 cookie, &iter_info); 578 579 if (ret && (mask & ALL_FSNOTIFY_PERM_EVENTS)) 580 goto out; 581 582 fsnotify_iter_next(&iter_info); 583 } 584 ret = 0; 585out: 586 srcu_read_unlock(&fsnotify_mark_srcu, iter_info.srcu_idx); 587 588 return ret; 589} 590EXPORT_SYMBOL_GPL(fsnotify); 591 592static __init int fsnotify_init(void) 593{ 594 int ret; 595 596 BUILD_BUG_ON(HWEIGHT32(ALL_FSNOTIFY_BITS) != 23); 597 598 ret = init_srcu_struct(&fsnotify_mark_srcu); 599 if (ret) 600 panic("initializing fsnotify_mark_srcu"); 601 602 fsnotify_mark_connector_cachep = KMEM_CACHE(fsnotify_mark_connector, 603 SLAB_PANIC); 604 605 return 0; 606} 607core_initcall(fsnotify_init); 608