fs/notify/fanotify/fanotify

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This source file includes following definitions.
fanotify_event_info_len
get_one_event
create_fd
finish_permission_event
process_access_response
copy_fid_to_user
copy_event_to_user
fanotify_poll
fanotify_read
fanotify_write
fanotify_release
fanotify_ioctl
fanotify_find_path
fanotify_mark_remove_from_mask
fanotify_remove_mark
fanotify_remove_vfsmount_mark
fanotify_remove_sb_mark
fanotify_remove_inode_mark
fanotify_mark_add_to_mask
fanotify_add_new_mark
fanotify_add_mark
fanotify_add_vfsmount_mark
fanotify_add_sb_mark
fanotify_add_inode_mark
SYSCALL_DEFINE2
fanotify_test_fid
fanotify_events_supported
do_fanotify_mark
SYSCALL_DEFINE5
COMPAT_SYSCALL_DEFINE6
fanotify_user_setup
   1 // SPDX-License-Identifier: GPL-2.0
   2 #include <linux/fanotify.h>
   3 #include <linux/fcntl.h>
   4 #include <linux/file.h>
   5 #include <linux/fs.h>
   6 #include <linux/anon_inodes.h>
   7 #include <linux/fsnotify_backend.h>
   8 #include <linux/init.h>
   9 #include <linux/mount.h>
  10 #include <linux/namei.h>
  11 #include <linux/poll.h>
  12 #include <linux/security.h>
  13 #include <linux/syscalls.h>
  14 #include <linux/slab.h>
  15 #include <linux/types.h>
  16 #include <linux/uaccess.h>
  17 #include <linux/compat.h>
  18 #include <linux/sched/signal.h>
  19 #include <linux/memcontrol.h>
  20 #include <linux/statfs.h>
  21 #include <linux/exportfs.h>
  22 
  23 #include <asm/ioctls.h>
  24 
  25 #include "../../mount.h"
  26 #include "../fdinfo.h"
  27 #include "fanotify.h"
  28 
  29 #define FANOTIFY_DEFAULT_MAX_EVENTS     16384
  30 #define FANOTIFY_DEFAULT_MAX_MARKS      8192
  31 #define FANOTIFY_DEFAULT_MAX_LISTENERS  128
  32 
  33 /*
  34  * All flags that may be specified in parameter event_f_flags of fanotify_init.
  35  *
  36  * Internal and external open flags are stored together in field f_flags of
  37  * struct file. Only external open flags shall be allowed in event_f_flags.
  38  * Internal flags like FMODE_NONOTIFY, FMODE_EXEC, FMODE_NOCMTIME shall be
  39  * excluded.
  40  */
  41 #define FANOTIFY_INIT_ALL_EVENT_F_BITS                          ( \
  42                 O_ACCMODE       | O_APPEND      | O_NONBLOCK    | \
  43                 __O_SYNC        | O_DSYNC       | O_CLOEXEC     | \
  44                 O_LARGEFILE     | O_NOATIME     )
  45 
  46 extern const struct fsnotify_ops fanotify_fsnotify_ops;
  47 
  48 struct kmem_cache *fanotify_mark_cache __read_mostly;
  49 struct kmem_cache *fanotify_event_cachep __read_mostly;
  50 struct kmem_cache *fanotify_perm_event_cachep __read_mostly;
  51 
  52 #define FANOTIFY_EVENT_ALIGN 4
  53 
  54 static int fanotify_event_info_len(struct fanotify_event *event)
  55 {
  56         if (!fanotify_event_has_fid(event))
  57                 return 0;
  58 
  59         return roundup(sizeof(struct fanotify_event_info_fid) +
  60                        sizeof(struct file_handle) + event->fh_len,
  61                        FANOTIFY_EVENT_ALIGN);
  62 }
  63 
  64 /*
  65  * Get an fsnotify notification event if one exists and is small
  66  * enough to fit in "count". Return an error pointer if the count
  67  * is not large enough. When permission event is dequeued, its state is
  68  * updated accordingly.
  69  */
  70 static struct fsnotify_event *get_one_event(struct fsnotify_group *group,
  71                                             size_t count)
  72 {
  73         size_t event_size = FAN_EVENT_METADATA_LEN;
  74         struct fsnotify_event *fsn_event = NULL;
  75 
  76         pr_debug("%s: group=%p count=%zd\n", __func__, group, count);
  77 
  78         spin_lock(&group->notification_lock);
  79         if (fsnotify_notify_queue_is_empty(group))
  80                 goto out;
  81 
  82         if (FAN_GROUP_FLAG(group, FAN_REPORT_FID)) {
  83                 event_size += fanotify_event_info_len(
  84                         FANOTIFY_E(fsnotify_peek_first_event(group)));
  85         }
  86 
  87         if (event_size > count) {
  88                 fsn_event = ERR_PTR(-EINVAL);
  89                 goto out;
  90         }
  91         fsn_event = fsnotify_remove_first_event(group);
  92         if (fanotify_is_perm_event(FANOTIFY_E(fsn_event)->mask))
  93                 FANOTIFY_PE(fsn_event)->state = FAN_EVENT_REPORTED;
  94 out:
  95         spin_unlock(&group->notification_lock);
  96         return fsn_event;
  97 }
  98 
  99 static int create_fd(struct fsnotify_group *group,
 100                      struct fanotify_event *event,
 101                      struct file **file)
 102 {
 103         int client_fd;
 104         struct file *new_file;
 105 
 106         pr_debug("%s: group=%p event=%p\n", __func__, group, event);
 107 
 108         client_fd = get_unused_fd_flags(group->fanotify_data.f_flags);
 109         if (client_fd < 0)
 110                 return client_fd;
 111 
 112         /*
 113          * we need a new file handle for the userspace program so it can read even if it was
 114          * originally opened O_WRONLY.
 115          */
 116         /* it's possible this event was an overflow event.  in that case dentry and mnt
 117          * are NULL;  That's fine, just don't call dentry open */
 118         if (event->path.dentry && event->path.mnt)
 119                 new_file = dentry_open(&event->path,
 120                                        group->fanotify_data.f_flags | FMODE_NONOTIFY,
 121                                        current_cred());
 122         else
 123                 new_file = ERR_PTR(-EOVERFLOW);
 124         if (IS_ERR(new_file)) {
 125                 /*
 126                  * we still send an event even if we can't open the file.  this
 127                  * can happen when say tasks are gone and we try to open their
 128                  * /proc files or we try to open a WRONLY file like in sysfs
 129                  * we just send the errno to userspace since there isn't much
 130                  * else we can do.
 131                  */
 132                 put_unused_fd(client_fd);
 133                 client_fd = PTR_ERR(new_file);
 134         } else {
 135                 *file = new_file;
 136         }
 137 
 138         return client_fd;
 139 }
 140 
 141 /*
 142  * Finish processing of permission event by setting it to ANSWERED state and
 143  * drop group->notification_lock.
 144  */
 145 static void finish_permission_event(struct fsnotify_group *group,
 146                                     struct fanotify_perm_event *event,
 147                                     unsigned int response)
 148                                     __releases(&group->notification_lock)
 149 {
 150         bool destroy = false;
 151 
 152         assert_spin_locked(&group->notification_lock);
 153         event->response = response;
 154         if (event->state == FAN_EVENT_CANCELED)
 155                 destroy = true;
 156         else
 157                 event->state = FAN_EVENT_ANSWERED;
 158         spin_unlock(&group->notification_lock);
 159         if (destroy)
 160                 fsnotify_destroy_event(group, &event->fae.fse);
 161 }
 162 
 163 static int process_access_response(struct fsnotify_group *group,
 164                                    struct fanotify_response *response_struct)
 165 {
 166         struct fanotify_perm_event *event;
 167         int fd = response_struct->fd;
 168         int response = response_struct->response;
 169 
 170         pr_debug("%s: group=%p fd=%d response=%d\n", __func__, group,
 171                  fd, response);
 172         /*
 173          * make sure the response is valid, if invalid we do nothing and either
 174          * userspace can send a valid response or we will clean it up after the
 175          * timeout
 176          */
 177         switch (response & ~FAN_AUDIT) {
 178         case FAN_ALLOW:
 179         case FAN_DENY:
 180                 break;
 181         default:
 182                 return -EINVAL;
 183         }
 184 
 185         if (fd < 0)
 186                 return -EINVAL;
 187 
 188         if ((response & FAN_AUDIT) && !FAN_GROUP_FLAG(group, FAN_ENABLE_AUDIT))
 189                 return -EINVAL;
 190 
 191         spin_lock(&group->notification_lock);
 192         list_for_each_entry(event, &group->fanotify_data.access_list,
 193                             fae.fse.list) {
 194                 if (event->fd != fd)
 195                         continue;
 196 
 197                 list_del_init(&event->fae.fse.list);
 198                 finish_permission_event(group, event, response);
 199                 wake_up(&group->fanotify_data.access_waitq);
 200                 return 0;
 201         }
 202         spin_unlock(&group->notification_lock);
 203 
 204         return -ENOENT;
 205 }
 206 
 207 static int copy_fid_to_user(struct fanotify_event *event, char __user *buf)
 208 {
 209         struct fanotify_event_info_fid info = { };
 210         struct file_handle handle = { };
 211         unsigned char bounce[FANOTIFY_INLINE_FH_LEN], *fh;
 212         size_t fh_len = event->fh_len;
 213         size_t len = fanotify_event_info_len(event);
 214 
 215         if (!len)
 216                 return 0;
 217 
 218         if (WARN_ON_ONCE(len < sizeof(info) + sizeof(handle) + fh_len))
 219                 return -EFAULT;
 220 
 221         /* Copy event info fid header followed by vaiable sized file handle */
 222         info.hdr.info_type = FAN_EVENT_INFO_TYPE_FID;
 223         info.hdr.len = len;
 224         info.fsid = event->fid.fsid;
 225         if (copy_to_user(buf, &info, sizeof(info)))
 226                 return -EFAULT;
 227 
 228         buf += sizeof(info);
 229         len -= sizeof(info);
 230         handle.handle_type = event->fh_type;
 231         handle.handle_bytes = fh_len;
 232         if (copy_to_user(buf, &handle, sizeof(handle)))
 233                 return -EFAULT;
 234 
 235         buf += sizeof(handle);
 236         len -= sizeof(handle);
 237         /*
 238          * For an inline fh, copy through stack to exclude the copy from
 239          * usercopy hardening protections.
 240          */
 241         fh = fanotify_event_fh(event);
 242         if (fh_len <= FANOTIFY_INLINE_FH_LEN) {
 243                 memcpy(bounce, fh, fh_len);
 244                 fh = bounce;
 245         }
 246         if (copy_to_user(buf, fh, fh_len))
 247                 return -EFAULT;
 248 
 249         /* Pad with 0's */
 250         buf += fh_len;
 251         len -= fh_len;
 252         WARN_ON_ONCE(len < 0 || len >= FANOTIFY_EVENT_ALIGN);
 253         if (len > 0 && clear_user(buf, len))
 254                 return -EFAULT;
 255 
 256         return 0;
 257 }
 258 
 259 static ssize_t copy_event_to_user(struct fsnotify_group *group,
 260                                   struct fsnotify_event *fsn_event,
 261                                   char __user *buf, size_t count)
 262 {
 263         struct fanotify_event_metadata metadata;
 264         struct fanotify_event *event;
 265         struct file *f = NULL;
 266         int ret, fd = FAN_NOFD;
 267 
 268         pr_debug("%s: group=%p event=%p\n", __func__, group, fsn_event);
 269 
 270         event = container_of(fsn_event, struct fanotify_event, fse);
 271         metadata.event_len = FAN_EVENT_METADATA_LEN;
 272         metadata.metadata_len = FAN_EVENT_METADATA_LEN;
 273         metadata.vers = FANOTIFY_METADATA_VERSION;
 274         metadata.reserved = 0;
 275         metadata.mask = event->mask & FANOTIFY_OUTGOING_EVENTS;
 276         metadata.pid = pid_vnr(event->pid);
 277 
 278         if (fanotify_event_has_path(event)) {
 279                 fd = create_fd(group, event, &f);
 280                 if (fd < 0)
 281                         return fd;
 282         } else if (fanotify_event_has_fid(event)) {
 283                 metadata.event_len += fanotify_event_info_len(event);
 284         }
 285         metadata.fd = fd;
 286 
 287         ret = -EFAULT;
 288         /*
 289          * Sanity check copy size in case get_one_event() and
 290          * fill_event_metadata() event_len sizes ever get out of sync.
 291          */
 292         if (WARN_ON_ONCE(metadata.event_len > count))
 293                 goto out_close_fd;
 294 
 295         if (copy_to_user(buf, &metadata, FAN_EVENT_METADATA_LEN))
 296                 goto out_close_fd;
 297 
 298         if (fanotify_is_perm_event(event->mask))
 299                 FANOTIFY_PE(fsn_event)->fd = fd;
 300 
 301         if (fanotify_event_has_path(event)) {
 302                 fd_install(fd, f);
 303         } else if (fanotify_event_has_fid(event)) {
 304                 ret = copy_fid_to_user(event, buf + FAN_EVENT_METADATA_LEN);
 305                 if (ret < 0)
 306                         return ret;
 307         }
 308 
 309         return metadata.event_len;
 310 
 311 out_close_fd:
 312         if (fd != FAN_NOFD) {
 313                 put_unused_fd(fd);
 314                 fput(f);
 315         }
 316         return ret;
 317 }
 318 
 319 /* intofiy userspace file descriptor functions */
 320 static __poll_t fanotify_poll(struct file *file, poll_table *wait)
 321 {
 322         struct fsnotify_group *group = file->private_data;
 323         __poll_t ret = 0;
 324 
 325         poll_wait(file, &group->notification_waitq, wait);
 326         spin_lock(&group->notification_lock);
 327         if (!fsnotify_notify_queue_is_empty(group))
 328                 ret = EPOLLIN | EPOLLRDNORM;
 329         spin_unlock(&group->notification_lock);
 330 
 331         return ret;
 332 }
 333 
 334 static ssize_t fanotify_read(struct file *file, char __user *buf,
 335                              size_t count, loff_t *pos)
 336 {
 337         struct fsnotify_group *group;
 338         struct fsnotify_event *kevent;
 339         char __user *start;
 340         int ret;
 341         DEFINE_WAIT_FUNC(wait, woken_wake_function);
 342 
 343         start = buf;
 344         group = file->private_data;
 345 
 346         pr_debug("%s: group=%p\n", __func__, group);
 347 
 348         add_wait_queue(&group->notification_waitq, &wait);
 349         while (1) {
 350                 kevent = get_one_event(group, count);
 351                 if (IS_ERR(kevent)) {
 352                         ret = PTR_ERR(kevent);
 353                         break;
 354                 }
 355 
 356                 if (!kevent) {
 357                         ret = -EAGAIN;
 358                         if (file->f_flags & O_NONBLOCK)
 359                                 break;
 360 
 361                         ret = -ERESTARTSYS;
 362                         if (signal_pending(current))
 363                                 break;
 364 
 365                         if (start != buf)
 366                                 break;
 367 
 368                         wait_woken(&wait, TASK_INTERRUPTIBLE, MAX_SCHEDULE_TIMEOUT);
 369                         continue;
 370                 }
 371 
 372                 ret = copy_event_to_user(group, kevent, buf, count);
 373                 if (unlikely(ret == -EOPENSTALE)) {
 374                         /*
 375                          * We cannot report events with stale fd so drop it.
 376                          * Setting ret to 0 will continue the event loop and
 377                          * do the right thing if there are no more events to
 378                          * read (i.e. return bytes read, -EAGAIN or wait).
 379                          */
 380                         ret = 0;
 381                 }
 382 
 383                 /*
 384                  * Permission events get queued to wait for response.  Other
 385                  * events can be destroyed now.
 386                  */
 387                 if (!fanotify_is_perm_event(FANOTIFY_E(kevent)->mask)) {
 388                         fsnotify_destroy_event(group, kevent);
 389                 } else {
 390                         if (ret <= 0) {
 391                                 spin_lock(&group->notification_lock);
 392                                 finish_permission_event(group,
 393                                         FANOTIFY_PE(kevent), FAN_DENY);
 394                                 wake_up(&group->fanotify_data.access_waitq);
 395                         } else {
 396                                 spin_lock(&group->notification_lock);
 397                                 list_add_tail(&kevent->list,
 398                                         &group->fanotify_data.access_list);
 399                                 spin_unlock(&group->notification_lock);
 400                         }
 401                 }
 402                 if (ret < 0)
 403                         break;
 404                 buf += ret;
 405                 count -= ret;
 406         }
 407         remove_wait_queue(&group->notification_waitq, &wait);
 408 
 409         if (start != buf && ret != -EFAULT)
 410                 ret = buf - start;
 411         return ret;
 412 }
 413 
 414 static ssize_t fanotify_write(struct file *file, const char __user *buf, size_t count, loff_t *pos)
 415 {
 416         struct fanotify_response response = { .fd = -1, .response = -1 };
 417         struct fsnotify_group *group;
 418         int ret;
 419 
 420         if (!IS_ENABLED(CONFIG_FANOTIFY_ACCESS_PERMISSIONS))
 421                 return -EINVAL;
 422 
 423         group = file->private_data;
 424 
 425         if (count > sizeof(response))
 426                 count = sizeof(response);
 427 
 428         pr_debug("%s: group=%p count=%zu\n", __func__, group, count);
 429 
 430         if (copy_from_user(&response, buf, count))
 431                 return -EFAULT;
 432 
 433         ret = process_access_response(group, &response);
 434         if (ret < 0)
 435                 count = ret;
 436 
 437         return count;
 438 }
 439 
 440 static int fanotify_release(struct inode *ignored, struct file *file)
 441 {
 442         struct fsnotify_group *group = file->private_data;
 443         struct fanotify_perm_event *event;
 444         struct fsnotify_event *fsn_event;
 445 
 446         /*
 447          * Stop new events from arriving in the notification queue. since
 448          * userspace cannot use fanotify fd anymore, no event can enter or
 449          * leave access_list by now either.
 450          */
 451         fsnotify_group_stop_queueing(group);
 452 
 453         /*
 454          * Process all permission events on access_list and notification queue
 455          * and simulate reply from userspace.
 456          */
 457         spin_lock(&group->notification_lock);
 458         while (!list_empty(&group->fanotify_data.access_list)) {
 459                 event = list_first_entry(&group->fanotify_data.access_list,
 460                                 struct fanotify_perm_event, fae.fse.list);
 461                 list_del_init(&event->fae.fse.list);
 462                 finish_permission_event(group, event, FAN_ALLOW);
 463                 spin_lock(&group->notification_lock);
 464         }
 465 
 466         /*
 467          * Destroy all non-permission events. For permission events just
 468          * dequeue them and set the response. They will be freed once the
 469          * response is consumed and fanotify_get_response() returns.
 470          */
 471         while (!fsnotify_notify_queue_is_empty(group)) {
 472                 fsn_event = fsnotify_remove_first_event(group);
 473                 if (!(FANOTIFY_E(fsn_event)->mask & FANOTIFY_PERM_EVENTS)) {
 474                         spin_unlock(&group->notification_lock);
 475                         fsnotify_destroy_event(group, fsn_event);
 476                 } else {
 477                         finish_permission_event(group, FANOTIFY_PE(fsn_event),
 478                                                 FAN_ALLOW);
 479                 }
 480                 spin_lock(&group->notification_lock);
 481         }
 482         spin_unlock(&group->notification_lock);
 483 
 484         /* Response for all permission events it set, wakeup waiters */
 485         wake_up(&group->fanotify_data.access_waitq);
 486 
 487         /* matches the fanotify_init->fsnotify_alloc_group */
 488         fsnotify_destroy_group(group);
 489 
 490         return 0;
 491 }
 492 
 493 static long fanotify_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 494 {
 495         struct fsnotify_group *group;
 496         struct fsnotify_event *fsn_event;
 497         void __user *p;
 498         int ret = -ENOTTY;
 499         size_t send_len = 0;
 500 
 501         group = file->private_data;
 502 
 503         p = (void __user *) arg;
 504 
 505         switch (cmd) {
 506         case FIONREAD:
 507                 spin_lock(&group->notification_lock);
 508                 list_for_each_entry(fsn_event, &group->notification_list, list)
 509                         send_len += FAN_EVENT_METADATA_LEN;
 510                 spin_unlock(&group->notification_lock);
 511                 ret = put_user(send_len, (int __user *) p);
 512                 break;
 513         }
 514 
 515         return ret;
 516 }
 517 
 518 static const struct file_operations fanotify_fops = {
 519         .show_fdinfo    = fanotify_show_fdinfo,
 520         .poll           = fanotify_poll,
 521         .read           = fanotify_read,
 522         .write          = fanotify_write,
 523         .fasync         = NULL,
 524         .release        = fanotify_release,
 525         .unlocked_ioctl = fanotify_ioctl,
 526         .compat_ioctl   = fanotify_ioctl,
 527         .llseek         = noop_llseek,
 528 };
 529 
 530 static int fanotify_find_path(int dfd, const char __user *filename,
 531                               struct path *path, unsigned int flags, __u64 mask,
 532                               unsigned int obj_type)
 533 {
 534         int ret;
 535 
 536         pr_debug("%s: dfd=%d filename=%p flags=%x\n", __func__,
 537                  dfd, filename, flags);
 538 
 539         if (filename == NULL) {
 540                 struct fd f = fdget(dfd);
 541 
 542                 ret = -EBADF;
 543                 if (!f.file)
 544                         goto out;
 545 
 546                 ret = -ENOTDIR;
 547                 if ((flags & FAN_MARK_ONLYDIR) &&
 548                     !(S_ISDIR(file_inode(f.file)->i_mode))) {
 549                         fdput(f);
 550                         goto out;
 551                 }
 552 
 553                 *path = f.file->f_path;
 554                 path_get(path);
 555                 fdput(f);
 556         } else {
 557                 unsigned int lookup_flags = 0;
 558 
 559                 if (!(flags & FAN_MARK_DONT_FOLLOW))
 560                         lookup_flags |= LOOKUP_FOLLOW;
 561                 if (flags & FAN_MARK_ONLYDIR)
 562                         lookup_flags |= LOOKUP_DIRECTORY;
 563 
 564                 ret = user_path_at(dfd, filename, lookup_flags, path);
 565                 if (ret)
 566                         goto out;
 567         }
 568 
 569         /* you can only watch an inode if you have read permissions on it */
 570         ret = inode_permission(path->dentry->d_inode, MAY_READ);
 571         if (ret) {
 572                 path_put(path);
 573                 goto out;
 574         }
 575 
 576         ret = security_path_notify(path, mask, obj_type);
 577         if (ret)
 578                 path_put(path);
 579 
 580 out:
 581         return ret;
 582 }
 583 
 584 static __u32 fanotify_mark_remove_from_mask(struct fsnotify_mark *fsn_mark,
 585                                             __u32 mask,
 586                                             unsigned int flags,
 587                                             int *destroy)
 588 {
 589         __u32 oldmask = 0;
 590 
 591         spin_lock(&fsn_mark->lock);
 592         if (!(flags & FAN_MARK_IGNORED_MASK)) {
 593                 oldmask = fsn_mark->mask;
 594                 fsn_mark->mask &= ~mask;
 595         } else {
 596                 fsn_mark->ignored_mask &= ~mask;
 597         }
 598         *destroy = !(fsn_mark->mask | fsn_mark->ignored_mask);
 599         spin_unlock(&fsn_mark->lock);
 600 
 601         return mask & oldmask;
 602 }
 603 
 604 static int fanotify_remove_mark(struct fsnotify_group *group,
 605                                 fsnotify_connp_t *connp, __u32 mask,
 606                                 unsigned int flags)
 607 {
 608         struct fsnotify_mark *fsn_mark = NULL;
 609         __u32 removed;
 610         int destroy_mark;
 611 
 612         mutex_lock(&group->mark_mutex);
 613         fsn_mark = fsnotify_find_mark(connp, group);
 614         if (!fsn_mark) {
 615                 mutex_unlock(&group->mark_mutex);
 616                 return -ENOENT;
 617         }
 618 
 619         removed = fanotify_mark_remove_from_mask(fsn_mark, mask, flags,
 620                                                  &destroy_mark);
 621         if (removed & fsnotify_conn_mask(fsn_mark->connector))
 622                 fsnotify_recalc_mask(fsn_mark->connector);
 623         if (destroy_mark)
 624                 fsnotify_detach_mark(fsn_mark);
 625         mutex_unlock(&group->mark_mutex);
 626         if (destroy_mark)
 627                 fsnotify_free_mark(fsn_mark);
 628 
 629         /* matches the fsnotify_find_mark() */
 630         fsnotify_put_mark(fsn_mark);
 631         return 0;
 632 }
 633 
 634 static int fanotify_remove_vfsmount_mark(struct fsnotify_group *group,
 635                                          struct vfsmount *mnt, __u32 mask,
 636                                          unsigned int flags)
 637 {
 638         return fanotify_remove_mark(group, &real_mount(mnt)->mnt_fsnotify_marks,
 639                                     mask, flags);
 640 }
 641 
 642 static int fanotify_remove_sb_mark(struct fsnotify_group *group,
 643                                       struct super_block *sb, __u32 mask,
 644                                       unsigned int flags)
 645 {
 646         return fanotify_remove_mark(group, &sb->s_fsnotify_marks, mask, flags);
 647 }
 648 
 649 static int fanotify_remove_inode_mark(struct fsnotify_group *group,
 650                                       struct inode *inode, __u32 mask,
 651                                       unsigned int flags)
 652 {
 653         return fanotify_remove_mark(group, &inode->i_fsnotify_marks, mask,
 654                                     flags);
 655 }
 656 
 657 static __u32 fanotify_mark_add_to_mask(struct fsnotify_mark *fsn_mark,
 658                                        __u32 mask,
 659                                        unsigned int flags)
 660 {
 661         __u32 oldmask = -1;
 662 
 663         spin_lock(&fsn_mark->lock);
 664         if (!(flags & FAN_MARK_IGNORED_MASK)) {
 665                 oldmask = fsn_mark->mask;
 666                 fsn_mark->mask |= mask;
 667         } else {
 668                 fsn_mark->ignored_mask |= mask;
 669                 if (flags & FAN_MARK_IGNORED_SURV_MODIFY)
 670                         fsn_mark->flags |= FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY;
 671         }
 672         spin_unlock(&fsn_mark->lock);
 673 
 674         return mask & ~oldmask;
 675 }
 676 
 677 static struct fsnotify_mark *fanotify_add_new_mark(struct fsnotify_group *group,
 678                                                    fsnotify_connp_t *connp,
 679                                                    unsigned int type,
 680                                                    __kernel_fsid_t *fsid)
 681 {
 682         struct fsnotify_mark *mark;
 683         int ret;
 684 
 685         if (atomic_read(&group->num_marks) > group->fanotify_data.max_marks)
 686                 return ERR_PTR(-ENOSPC);
 687 
 688         mark = kmem_cache_alloc(fanotify_mark_cache, GFP_KERNEL);
 689         if (!mark)
 690                 return ERR_PTR(-ENOMEM);
 691 
 692         fsnotify_init_mark(mark, group);
 693         ret = fsnotify_add_mark_locked(mark, connp, type, 0, fsid);
 694         if (ret) {
 695                 fsnotify_put_mark(mark);
 696                 return ERR_PTR(ret);
 697         }
 698 
 699         return mark;
 700 }
 701 
 702 
 703 static int fanotify_add_mark(struct fsnotify_group *group,
 704                              fsnotify_connp_t *connp, unsigned int type,
 705                              __u32 mask, unsigned int flags,
 706                              __kernel_fsid_t *fsid)
 707 {
 708         struct fsnotify_mark *fsn_mark;
 709         __u32 added;
 710 
 711         mutex_lock(&group->mark_mutex);
 712         fsn_mark = fsnotify_find_mark(connp, group);
 713         if (!fsn_mark) {
 714                 fsn_mark = fanotify_add_new_mark(group, connp, type, fsid);
 715                 if (IS_ERR(fsn_mark)) {
 716                         mutex_unlock(&group->mark_mutex);
 717                         return PTR_ERR(fsn_mark);
 718                 }
 719         }
 720         added = fanotify_mark_add_to_mask(fsn_mark, mask, flags);
 721         if (added & ~fsnotify_conn_mask(fsn_mark->connector))
 722                 fsnotify_recalc_mask(fsn_mark->connector);
 723         mutex_unlock(&group->mark_mutex);
 724 
 725         fsnotify_put_mark(fsn_mark);
 726         return 0;
 727 }
 728 
 729 static int fanotify_add_vfsmount_mark(struct fsnotify_group *group,
 730                                       struct vfsmount *mnt, __u32 mask,
 731                                       unsigned int flags, __kernel_fsid_t *fsid)
 732 {
 733         return fanotify_add_mark(group, &real_mount(mnt)->mnt_fsnotify_marks,
 734                                  FSNOTIFY_OBJ_TYPE_VFSMOUNT, mask, flags, fsid);
 735 }
 736 
 737 static int fanotify_add_sb_mark(struct fsnotify_group *group,
 738                                 struct super_block *sb, __u32 mask,
 739                                 unsigned int flags, __kernel_fsid_t *fsid)
 740 {
 741         return fanotify_add_mark(group, &sb->s_fsnotify_marks,
 742                                  FSNOTIFY_OBJ_TYPE_SB, mask, flags, fsid);
 743 }
 744 
 745 static int fanotify_add_inode_mark(struct fsnotify_group *group,
 746                                    struct inode *inode, __u32 mask,
 747                                    unsigned int flags, __kernel_fsid_t *fsid)
 748 {
 749         pr_debug("%s: group=%p inode=%p\n", __func__, group, inode);
 750 
 751         /*
 752          * If some other task has this inode open for write we should not add
 753          * an ignored mark, unless that ignored mark is supposed to survive
 754          * modification changes anyway.
 755          */
 756         if ((flags & FAN_MARK_IGNORED_MASK) &&
 757             !(flags & FAN_MARK_IGNORED_SURV_MODIFY) &&
 758             inode_is_open_for_write(inode))
 759                 return 0;
 760 
 761         return fanotify_add_mark(group, &inode->i_fsnotify_marks,
 762                                  FSNOTIFY_OBJ_TYPE_INODE, mask, flags, fsid);
 763 }
 764 
 765 /* fanotify syscalls */
 766 SYSCALL_DEFINE2(fanotify_init, unsigned int, flags, unsigned int, event_f_flags)
 767 {
 768         struct fsnotify_group *group;
 769         int f_flags, fd;
 770         struct user_struct *user;
 771         struct fanotify_event *oevent;
 772 
 773         pr_debug("%s: flags=%x event_f_flags=%x\n",
 774                  __func__, flags, event_f_flags);
 775 
 776         if (!capable(CAP_SYS_ADMIN))
 777                 return -EPERM;
 778 
 779 #ifdef CONFIG_AUDITSYSCALL
 780         if (flags & ~(FANOTIFY_INIT_FLAGS | FAN_ENABLE_AUDIT))
 781 #else
 782         if (flags & ~FANOTIFY_INIT_FLAGS)
 783 #endif
 784                 return -EINVAL;
 785 
 786         if (event_f_flags & ~FANOTIFY_INIT_ALL_EVENT_F_BITS)
 787                 return -EINVAL;
 788 
 789         switch (event_f_flags & O_ACCMODE) {
 790         case O_RDONLY:
 791         case O_RDWR:
 792         case O_WRONLY:
 793                 break;
 794         default:
 795                 return -EINVAL;
 796         }
 797 
 798         if ((flags & FAN_REPORT_FID) &&
 799             (flags & FANOTIFY_CLASS_BITS) != FAN_CLASS_NOTIF)
 800                 return -EINVAL;
 801 
 802         user = get_current_user();
 803         if (atomic_read(&user->fanotify_listeners) > FANOTIFY_DEFAULT_MAX_LISTENERS) {
 804                 free_uid(user);
 805                 return -EMFILE;
 806         }
 807 
 808         f_flags = O_RDWR | FMODE_NONOTIFY;
 809         if (flags & FAN_CLOEXEC)
 810                 f_flags |= O_CLOEXEC;
 811         if (flags & FAN_NONBLOCK)
 812                 f_flags |= O_NONBLOCK;
 813 
 814         /* fsnotify_alloc_group takes a ref.  Dropped in fanotify_release */
 815         group = fsnotify_alloc_group(&fanotify_fsnotify_ops);
 816         if (IS_ERR(group)) {
 817                 free_uid(user);
 818                 return PTR_ERR(group);
 819         }
 820 
 821         group->fanotify_data.user = user;
 822         group->fanotify_data.flags = flags;
 823         atomic_inc(&user->fanotify_listeners);
 824         group->memcg = get_mem_cgroup_from_mm(current->mm);
 825 
 826         oevent = fanotify_alloc_event(group, NULL, FS_Q_OVERFLOW, NULL,
 827                                       FSNOTIFY_EVENT_NONE, NULL);
 828         if (unlikely(!oevent)) {
 829                 fd = -ENOMEM;
 830                 goto out_destroy_group;
 831         }
 832         group->overflow_event = &oevent->fse;
 833 
 834         if (force_o_largefile())
 835                 event_f_flags |= O_LARGEFILE;
 836         group->fanotify_data.f_flags = event_f_flags;
 837         init_waitqueue_head(&group->fanotify_data.access_waitq);
 838         INIT_LIST_HEAD(&group->fanotify_data.access_list);
 839         switch (flags & FANOTIFY_CLASS_BITS) {
 840         case FAN_CLASS_NOTIF:
 841                 group->priority = FS_PRIO_0;
 842                 break;
 843         case FAN_CLASS_CONTENT:
 844                 group->priority = FS_PRIO_1;
 845                 break;
 846         case FAN_CLASS_PRE_CONTENT:
 847                 group->priority = FS_PRIO_2;
 848                 break;
 849         default:
 850                 fd = -EINVAL;
 851                 goto out_destroy_group;
 852         }
 853 
 854         if (flags & FAN_UNLIMITED_QUEUE) {
 855                 fd = -EPERM;
 856                 if (!capable(CAP_SYS_ADMIN))
 857                         goto out_destroy_group;
 858                 group->max_events = UINT_MAX;
 859         } else {
 860                 group->max_events = FANOTIFY_DEFAULT_MAX_EVENTS;
 861         }
 862 
 863         if (flags & FAN_UNLIMITED_MARKS) {
 864                 fd = -EPERM;
 865                 if (!capable(CAP_SYS_ADMIN))
 866                         goto out_destroy_group;
 867                 group->fanotify_data.max_marks = UINT_MAX;
 868         } else {
 869                 group->fanotify_data.max_marks = FANOTIFY_DEFAULT_MAX_MARKS;
 870         }
 871 
 872         if (flags & FAN_ENABLE_AUDIT) {
 873                 fd = -EPERM;
 874                 if (!capable(CAP_AUDIT_WRITE))
 875                         goto out_destroy_group;
 876         }
 877 
 878         fd = anon_inode_getfd("[fanotify]", &fanotify_fops, group, f_flags);
 879         if (fd < 0)
 880                 goto out_destroy_group;
 881 
 882         return fd;
 883 
 884 out_destroy_group:
 885         fsnotify_destroy_group(group);
 886         return fd;
 887 }
 888 
 889 /* Check if filesystem can encode a unique fid */
 890 static int fanotify_test_fid(struct path *path, __kernel_fsid_t *fsid)
 891 {
 892         __kernel_fsid_t root_fsid;
 893         int err;
 894 
 895         /*
 896          * Make sure path is not in filesystem with zero fsid (e.g. tmpfs).
 897          */
 898         err = vfs_get_fsid(path->dentry, fsid);
 899         if (err)
 900                 return err;
 901 
 902         if (!fsid->val[0] && !fsid->val[1])
 903                 return -ENODEV;
 904 
 905         /*
 906          * Make sure path is not inside a filesystem subvolume (e.g. btrfs)
 907          * which uses a different fsid than sb root.
 908          */
 909         err = vfs_get_fsid(path->dentry->d_sb->s_root, &root_fsid);
 910         if (err)
 911                 return err;
 912 
 913         if (root_fsid.val[0] != fsid->val[0] ||
 914             root_fsid.val[1] != fsid->val[1])
 915                 return -EXDEV;
 916 
 917         /*
 918          * We need to make sure that the file system supports at least
 919          * encoding a file handle so user can use name_to_handle_at() to
 920          * compare fid returned with event to the file handle of watched
 921          * objects. However, name_to_handle_at() requires that the
 922          * filesystem also supports decoding file handles.
 923          */
 924         if (!path->dentry->d_sb->s_export_op ||
 925             !path->dentry->d_sb->s_export_op->fh_to_dentry)
 926                 return -EOPNOTSUPP;
 927 
 928         return 0;
 929 }
 930 
 931 static int fanotify_events_supported(struct path *path, __u64 mask)
 932 {
 933         /*
 934          * Some filesystems such as 'proc' acquire unusual locks when opening
 935          * files. For them fanotify permission events have high chances of
 936          * deadlocking the system - open done when reporting fanotify event
 937          * blocks on this "unusual" lock while another process holding the lock
 938          * waits for fanotify permission event to be answered. Just disallow
 939          * permission events for such filesystems.
 940          */
 941         if (mask & FANOTIFY_PERM_EVENTS &&
 942             path->mnt->mnt_sb->s_type->fs_flags & FS_DISALLOW_NOTIFY_PERM)
 943                 return -EINVAL;
 944         return 0;
 945 }
 946 
 947 static int do_fanotify_mark(int fanotify_fd, unsigned int flags, __u64 mask,
 948                             int dfd, const char  __user *pathname)
 949 {
 950         struct inode *inode = NULL;
 951         struct vfsmount *mnt = NULL;
 952         struct fsnotify_group *group;
 953         struct fd f;
 954         struct path path;
 955         __kernel_fsid_t __fsid, *fsid = NULL;
 956         u32 valid_mask = FANOTIFY_EVENTS | FANOTIFY_EVENT_FLAGS;
 957         unsigned int mark_type = flags & FANOTIFY_MARK_TYPE_BITS;
 958         unsigned int obj_type;
 959         int ret;
 960 
 961         pr_debug("%s: fanotify_fd=%d flags=%x dfd=%d pathname=%p mask=%llx\n",
 962                  __func__, fanotify_fd, flags, dfd, pathname, mask);
 963 
 964         /* we only use the lower 32 bits as of right now. */
 965         if (mask & ((__u64)0xffffffff << 32))
 966                 return -EINVAL;
 967 
 968         if (flags & ~FANOTIFY_MARK_FLAGS)
 969                 return -EINVAL;
 970 
 971         switch (mark_type) {
 972         case FAN_MARK_INODE:
 973                 obj_type = FSNOTIFY_OBJ_TYPE_INODE;
 974                 break;
 975         case FAN_MARK_MOUNT:
 976                 obj_type = FSNOTIFY_OBJ_TYPE_VFSMOUNT;
 977                 break;
 978         case FAN_MARK_FILESYSTEM:
 979                 obj_type = FSNOTIFY_OBJ_TYPE_SB;
 980                 break;
 981         default:
 982                 return -EINVAL;
 983         }
 984 
 985         switch (flags & (FAN_MARK_ADD | FAN_MARK_REMOVE | FAN_MARK_FLUSH)) {
 986         case FAN_MARK_ADD:              /* fallthrough */
 987         case FAN_MARK_REMOVE:
 988                 if (!mask)
 989                         return -EINVAL;
 990                 break;
 991         case FAN_MARK_FLUSH:
 992                 if (flags & ~(FANOTIFY_MARK_TYPE_BITS | FAN_MARK_FLUSH))
 993                         return -EINVAL;
 994                 break;
 995         default:
 996                 return -EINVAL;
 997         }
 998 
 999         if (IS_ENABLED(CONFIG_FANOTIFY_ACCESS_PERMISSIONS))
1000                 valid_mask |= FANOTIFY_PERM_EVENTS;
1001 
1002         if (mask & ~valid_mask)
1003                 return -EINVAL;
1004 
1005         f = fdget(fanotify_fd);
1006         if (unlikely(!f.file))
1007                 return -EBADF;
1008 
1009         /* verify that this is indeed an fanotify instance */
1010         ret = -EINVAL;
1011         if (unlikely(f.file->f_op != &fanotify_fops))
1012                 goto fput_and_out;
1013         group = f.file->private_data;
1014 
1015         /*
1016          * group->priority == FS_PRIO_0 == FAN_CLASS_NOTIF.  These are not
1017          * allowed to set permissions events.
1018          */
1019         ret = -EINVAL;
1020         if (mask & FANOTIFY_PERM_EVENTS &&
1021             group->priority == FS_PRIO_0)
1022                 goto fput_and_out;
1023 
1024         /*
1025          * Events with data type inode do not carry enough information to report
1026          * event->fd, so we do not allow setting a mask for inode events unless
1027          * group supports reporting fid.
1028          * inode events are not supported on a mount mark, because they do not
1029          * carry enough information (i.e. path) to be filtered by mount point.
1030          */
1031         if (mask & FANOTIFY_INODE_EVENTS &&
1032             (!FAN_GROUP_FLAG(group, FAN_REPORT_FID) ||
1033              mark_type == FAN_MARK_MOUNT))
1034                 goto fput_and_out;
1035 
1036         if (flags & FAN_MARK_FLUSH) {
1037                 ret = 0;
1038                 if (mark_type == FAN_MARK_MOUNT)
1039                         fsnotify_clear_vfsmount_marks_by_group(group);
1040                 else if (mark_type == FAN_MARK_FILESYSTEM)
1041                         fsnotify_clear_sb_marks_by_group(group);
1042                 else
1043                         fsnotify_clear_inode_marks_by_group(group);
1044                 goto fput_and_out;
1045         }
1046 
1047         ret = fanotify_find_path(dfd, pathname, &path, flags,
1048                         (mask & ALL_FSNOTIFY_EVENTS), obj_type);
1049         if (ret)
1050                 goto fput_and_out;
1051 
1052         if (flags & FAN_MARK_ADD) {
1053                 ret = fanotify_events_supported(&path, mask);
1054                 if (ret)
1055                         goto path_put_and_out;
1056         }
1057 
1058         if (FAN_GROUP_FLAG(group, FAN_REPORT_FID)) {
1059                 ret = fanotify_test_fid(&path, &__fsid);
1060                 if (ret)
1061                         goto path_put_and_out;
1062 
1063                 fsid = &__fsid;
1064         }
1065 
1066         /* inode held in place by reference to path; group by fget on fd */
1067         if (mark_type == FAN_MARK_INODE)
1068                 inode = path.dentry->d_inode;
1069         else
1070                 mnt = path.mnt;
1071 
1072         /* create/update an inode mark */
1073         switch (flags & (FAN_MARK_ADD | FAN_MARK_REMOVE)) {
1074         case FAN_MARK_ADD:
1075                 if (mark_type == FAN_MARK_MOUNT)
1076                         ret = fanotify_add_vfsmount_mark(group, mnt, mask,
1077                                                          flags, fsid);
1078                 else if (mark_type == FAN_MARK_FILESYSTEM)
1079                         ret = fanotify_add_sb_mark(group, mnt->mnt_sb, mask,
1080                                                    flags, fsid);
1081                 else
1082                         ret = fanotify_add_inode_mark(group, inode, mask,
1083                                                       flags, fsid);
1084                 break;
1085         case FAN_MARK_REMOVE:
1086                 if (mark_type == FAN_MARK_MOUNT)
1087                         ret = fanotify_remove_vfsmount_mark(group, mnt, mask,
1088                                                             flags);
1089                 else if (mark_type == FAN_MARK_FILESYSTEM)
1090                         ret = fanotify_remove_sb_mark(group, mnt->mnt_sb, mask,
1091                                                       flags);
1092                 else
1093                         ret = fanotify_remove_inode_mark(group, inode, mask,
1094                                                          flags);
1095                 break;
1096         default:
1097                 ret = -EINVAL;
1098         }
1099 
1100 path_put_and_out:
1101         path_put(&path);
1102 fput_and_out:
1103         fdput(f);
1104         return ret;
1105 }
1106 
1107 SYSCALL_DEFINE5(fanotify_mark, int, fanotify_fd, unsigned int, flags,
1108                               __u64, mask, int, dfd,
1109                               const char  __user *, pathname)
1110 {
1111         return do_fanotify_mark(fanotify_fd, flags, mask, dfd, pathname);
1112 }
1113 
1114 #ifdef CONFIG_COMPAT
1115 COMPAT_SYSCALL_DEFINE6(fanotify_mark,
1116                                 int, fanotify_fd, unsigned int, flags,
1117                                 __u32, mask0, __u32, mask1, int, dfd,
1118                                 const char  __user *, pathname)
1119 {
1120         return do_fanotify_mark(fanotify_fd, flags,
1121 #ifdef __BIG_ENDIAN
1122                                 ((__u64)mask0 << 32) | mask1,
1123 #else
1124                                 ((__u64)mask1 << 32) | mask0,
1125 #endif
1126                                  dfd, pathname);
1127 }
1128 #endif
1129 
1130 /*
1131  * fanotify_user_setup - Our initialization function.  Note that we cannot return
1132  * error because we have compiled-in VFS hooks.  So an (unlikely) failure here
1133  * must result in panic().
1134  */
1135 static int __init fanotify_user_setup(void)
1136 {
1137         BUILD_BUG_ON(HWEIGHT32(FANOTIFY_INIT_FLAGS) != 8);
1138         BUILD_BUG_ON(HWEIGHT32(FANOTIFY_MARK_FLAGS) != 9);
1139 
1140         fanotify_mark_cache = KMEM_CACHE(fsnotify_mark,
1141                                          SLAB_PANIC|SLAB_ACCOUNT);
1142         fanotify_event_cachep = KMEM_CACHE(fanotify_event, SLAB_PANIC);
1143         if (IS_ENABLED(CONFIG_FANOTIFY_ACCESS_PERMISSIONS)) {
1144                 fanotify_perm_event_cachep =
1145                         KMEM_CACHE(fanotify_perm_event, SLAB_PANIC);
1146         }
1147 
1148         return 0;
1149 }
1150 device_initcall(fanotify_user_setup);
/* [<][>][^][v][top][bottom][index][help] */
root/fs/notify/fanotify/fanotify_user.c

DEFINITIONS
