fs/notify/fanotify/fanotify_user.c

   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
  20 #include <asm/ioctls.h>
  21
  22 #include "../../mount.h"
  23 #include "../fdinfo.h"
  24 #include "fanotify.h"
  25
  26 #define FANOTIFY_DEFAULT_MAX_EVENTS     16384
  27 #define FANOTIFY_DEFAULT_MAX_MARKS      8192
  28 #define FANOTIFY_DEFAULT_MAX_LISTENERS  128
  29
  30 /*
  31  * All flags that may be specified in parameter event_f_flags of fanotify_init.
  32  *
  33  * Internal and external open flags are stored together in field f_flags of
  34  * struct file. Only external open flags shall be allowed in event_f_flags.
  35  * Internal flags like FMODE_NONOTIFY, FMODE_EXEC, FMODE_NOCMTIME shall be
  36  * excluded.
  37  */
  38 #define FANOTIFY_INIT_ALL_EVENT_F_BITS                          ( \
  39                 O_ACCMODE       | O_APPEND      | O_NONBLOCK    | \
  40                 __O_SYNC        | O_DSYNC       | O_CLOEXEC     | \
  41                 O_LARGEFILE     | O_NOATIME     )
  42
  43 extern const struct fsnotify_ops fanotify_fsnotify_ops;
  44
  45 struct kmem_cache *fanotify_mark_cache __read_mostly;
  46 struct kmem_cache *fanotify_event_cachep __read_mostly;
  47 struct kmem_cache *fanotify_perm_event_cachep __read_mostly;
  48
  49 /*
  50  * Get an fsnotify notification event if one exists and is small
  51  * enough to fit in "count". Return an error pointer if the count
  52  * is not large enough.
  53  *
  54  * Called with the group->notification_lock held.
  55  */
  56 static struct fsnotify_event *get_one_event(struct fsnotify_group *group,
  57                                             size_t count)
  58 {
  59         assert_spin_locked(&group->notification_lock);
  60
  61         pr_debug("%s: group=%p count=%zd\n", __func__, group, count);
  62
  63         if (fsnotify_notify_queue_is_empty(group))
  64                 return NULL;
  65
  66         if (FAN_EVENT_METADATA_LEN > count)
  67                 return ERR_PTR(-EINVAL);
  68
  69         /* held the notification_lock the whole time, so this is the
  70          * same event we peeked above */
  71         return fsnotify_remove_first_event(group);
  72 }
  73
  74 static int create_fd(struct fsnotify_group *group,
  75                      struct fanotify_event_info *event,
  76                      struct file **file)
  77 {
  78         int client_fd;
  79         struct file *new_file;
  80
  81         pr_debug("%s: group=%p event=%p\n", __func__, group, event);
  82
  83         client_fd = get_unused_fd_flags(group->fanotify_data.f_flags);
  84         if (client_fd < 0)
  85                 return client_fd;
  86
  87         /*
  88          * we need a new file handle for the userspace program so it can read even if it was
  89          * originally opened O_WRONLY.
  90          */
  91         /* it's possible this event was an overflow event.  in that case dentry and mnt
  92          * are NULL;  That's fine, just don't call dentry open */
  93         if (event->path.dentry && event->path.mnt)
  94                 new_file = dentry_open(&event->path,
  95                                        group->fanotify_data.f_flags | FMODE_NONOTIFY,
  96                                        current_cred());
  97         else
  98                 new_file = ERR_PTR(-EOVERFLOW);
  99         if (IS_ERR(new_file)) {
 100                 /*
 101                  * we still send an event even if we can't open the file.  this
 102                  * can happen when say tasks are gone and we try to open their
 103                  * /proc files or we try to open a WRONLY file like in sysfs
 104                  * we just send the errno to userspace since there isn't much
 105                  * else we can do.
 106                  */
 107                 put_unused_fd(client_fd);
 108                 client_fd = PTR_ERR(new_file);
 109         } else {
 110                 *file = new_file;
 111         }
 112
 113         return client_fd;
 114 }
 115
 116 static int fill_event_metadata(struct fsnotify_group *group,
 117                                struct fanotify_event_metadata *metadata,
 118                                struct fsnotify_event *fsn_event,
 119                                struct file **file)
 120 {
 121         int ret = 0;
 122         struct fanotify_event_info *event;
 123
 124         pr_debug("%s: group=%p metadata=%p event=%p\n", __func__,
 125                  group, metadata, fsn_event);
 126
 127         *file = NULL;
 128         event = container_of(fsn_event, struct fanotify_event_info, fse);
 129         metadata->event_len = FAN_EVENT_METADATA_LEN;
 130         metadata->metadata_len = FAN_EVENT_METADATA_LEN;
 131         metadata->vers = FANOTIFY_METADATA_VERSION;
 132         metadata->reserved = 0;
 133         metadata->mask = fsn_event->mask & FAN_ALL_OUTGOING_EVENTS;
 134         metadata->pid = pid_vnr(event->tgid);
 135         if (unlikely(fsn_event->mask & FAN_Q_OVERFLOW))
 136                 metadata->fd = FAN_NOFD;
 137         else {
 138                 metadata->fd = create_fd(group, event, file);
 139                 if (metadata->fd < 0)
 140                         ret = metadata->fd;
 141         }
 142
 143         return ret;
 144 }
 145
 146 static struct fanotify_perm_event_info *dequeue_event(
 147                                 struct fsnotify_group *group, int fd)
 148 {
 149         struct fanotify_perm_event_info *event, *return_e = NULL;
 150
 151         spin_lock(&group->notification_lock);
 152         list_for_each_entry(event, &group->fanotify_data.access_list,
 153                             fae.fse.list) {
 154                 if (event->fd != fd)
 155                         continue;
 156
 157                 list_del_init(&event->fae.fse.list);
 158                 return_e = event;
 159                 break;
 160         }
 161         spin_unlock(&group->notification_lock);
 162
 163         pr_debug("%s: found return_re=%p\n", __func__, return_e);
 164
 165         return return_e;
 166 }
 167
 168 static int process_access_response(struct fsnotify_group *group,
 169                                    struct fanotify_response *response_struct)
 170 {
 171         struct fanotify_perm_event_info *event;
 172         int fd = response_struct->fd;
 173         int response = response_struct->response;
 174
 175         pr_debug("%s: group=%p fd=%d response=%d\n", __func__, group,
 176                  fd, response);
 177         /*
 178          * make sure the response is valid, if invalid we do nothing and either
 179          * userspace can send a valid response or we will clean it up after the
 180          * timeout
 181          */
 182         switch (response & ~FAN_AUDIT) {
 183         case FAN_ALLOW:
 184         case FAN_DENY:
 185                 break;
 186         default:
 187                 return -EINVAL;
 188         }
 189
 190         if (fd < 0)
 191                 return -EINVAL;
 192
 193         if ((response & FAN_AUDIT) && !group->fanotify_data.audit)
 194                 return -EINVAL;
 195
 196         event = dequeue_event(group, fd);
 197         if (!event)
 198                 return -ENOENT;
 199
 200         event->response = response;
 201         wake_up(&group->fanotify_data.access_waitq);
 202
 203         return 0;
 204 }
 205
 206 static ssize_t copy_event_to_user(struct fsnotify_group *group,
 207                                   struct fsnotify_event *event,
 208                                   char __user *buf)
 209 {
 210         struct fanotify_event_metadata fanotify_event_metadata;
 211         struct file *f;
 212         int fd, ret;
 213
 214         pr_debug("%s: group=%p event=%p\n", __func__, group, event);
 215
 216         ret = fill_event_metadata(group, &fanotify_event_metadata, event, &f);
 217         if (ret < 0)
 218                 return ret;
 219
 220         fd = fanotify_event_metadata.fd;
 221         ret = -EFAULT;
 222         if (copy_to_user(buf, &fanotify_event_metadata,
 223                          fanotify_event_metadata.event_len))
 224                 goto out_close_fd;
 225
 226         if (fanotify_is_perm_event(event->mask))
 227                 FANOTIFY_PE(event)->fd = fd;
 228
 229         if (fd != FAN_NOFD)
 230                 fd_install(fd, f);
 231         return fanotify_event_metadata.event_len;
 232
 233 out_close_fd:
 234         if (fd != FAN_NOFD) {
 235                 put_unused_fd(fd);
 236                 fput(f);
 237         }
 238         return ret;
 239 }
 240
 241 /* intofiy userspace file descriptor functions */
 242 static __poll_t fanotify_poll(struct file *file, poll_table *wait)
 243 {
 244         struct fsnotify_group *group = file->private_data;
 245         __poll_t ret = 0;
 246
 247         poll_wait(file, &group->notification_waitq, wait);
 248         spin_lock(&group->notification_lock);
 249         if (!fsnotify_notify_queue_is_empty(group))
 250                 ret = EPOLLIN | EPOLLRDNORM;
 251         spin_unlock(&group->notification_lock);
 252
 253         return ret;
 254 }
 255
 256 static ssize_t fanotify_read(struct file *file, char __user *buf,
 257                              size_t count, loff_t *pos)
 258 {
 259         struct fsnotify_group *group;
 260         struct fsnotify_event *kevent;
 261         char __user *start;
 262         int ret;
 263         DEFINE_WAIT_FUNC(wait, woken_wake_function);
 264
 265         start = buf;
 266         group = file->private_data;
 267
 268         pr_debug("%s: group=%p\n", __func__, group);
 269
 270         add_wait_queue(&group->notification_waitq, &wait);
 271         while (1) {
 272                 spin_lock(&group->notification_lock);
 273                 kevent = get_one_event(group, count);
 274                 spin_unlock(&group->notification_lock);
 275
 276                 if (IS_ERR(kevent)) {
 277                         ret = PTR_ERR(kevent);
 278                         break;
 279                 }
 280
 281                 if (!kevent) {
 282                         ret = -EAGAIN;
 283                         if (file->f_flags & O_NONBLOCK)
 284                                 break;
 285
 286                         ret = -ERESTARTSYS;
 287                         if (signal_pending(current))
 288                                 break;
 289
 290                         if (start != buf)
 291                                 break;
 292
 293                         wait_woken(&wait, TASK_INTERRUPTIBLE, MAX_SCHEDULE_TIMEOUT);
 294                         continue;
 295                 }
 296
 297                 ret = copy_event_to_user(group, kevent, buf);
 298                 if (unlikely(ret == -EOPENSTALE)) {
 299                         /*
 300                          * We cannot report events with stale fd so drop it.
 301                          * Setting ret to 0 will continue the event loop and
 302                          * do the right thing if there are no more events to
 303                          * read (i.e. return bytes read, -EAGAIN or wait).
 304                          */
 305                         ret = 0;
 306                 }
 307
 308                 /*
 309                  * Permission events get queued to wait for response.  Other
 310                  * events can be destroyed now.
 311                  */
 312                 if (!fanotify_is_perm_event(kevent->mask)) {
 313                         fsnotify_destroy_event(group, kevent);
 314                 } else {
 315                         if (ret <= 0) {
 316                                 FANOTIFY_PE(kevent)->response = FAN_DENY;
 317                                 wake_up(&group->fanotify_data.access_waitq);
 318                         } else {
 319                                 spin_lock(&group->notification_lock);
 320                                 list_add_tail(&kevent->list,
 321                                         &group->fanotify_data.access_list);
 322                                 spin_unlock(&group->notification_lock);
 323                         }
 324                 }
 325                 if (ret < 0)
 326                         break;
 327                 buf += ret;
 328                 count -= ret;
 329         }
 330         remove_wait_queue(&group->notification_waitq, &wait);
 331
 332         if (start != buf && ret != -EFAULT)
 333                 ret = buf - start;
 334         return ret;
 335 }
 336
 337 static ssize_t fanotify_write(struct file *file, const char __user *buf, size_t count, loff_t *pos)
 338 {
 339         struct fanotify_response response = { .fd = -1, .response = -1 };
 340         struct fsnotify_group *group;
 341         int ret;
 342
 343         if (!IS_ENABLED(CONFIG_FANOTIFY_ACCESS_PERMISSIONS))
 344                 return -EINVAL;
 345
 346         group = file->private_data;
 347
 348         if (count > sizeof(response))
 349                 count = sizeof(response);
 350
 351         pr_debug("%s: group=%p count=%zu\n", __func__, group, count);
 352
 353         if (copy_from_user(&response, buf, count))
 354                 return -EFAULT;
 355
 356         ret = process_access_response(group, &response);
 357         if (ret < 0)
 358                 count = ret;
 359
 360         return count;
 361 }
 362
 363 static int fanotify_release(struct inode *ignored, struct file *file)
 364 {
 365         struct fsnotify_group *group = file->private_data;
 366         struct fanotify_perm_event_info *event, *next;
 367         struct fsnotify_event *fsn_event;
 368
 369         /*
 370          * Stop new events from arriving in the notification queue. since
 371          * userspace cannot use fanotify fd anymore, no event can enter or
 372          * leave access_list by now either.
 373          */
 374         fsnotify_group_stop_queueing(group);
 375
 376         /*
 377          * Process all permission events on access_list and notification queue
 378          * and simulate reply from userspace.
 379          */
 380         spin_lock(&group->notification_lock);
 381         list_for_each_entry_safe(event, next, &group->fanotify_data.access_list,
 382                                  fae.fse.list) {
 383                 pr_debug("%s: found group=%p event=%p\n", __func__, group,
 384                          event);
 385
 386                 list_del_init(&event->fae.fse.list);
 387                 event->response = FAN_ALLOW;
 388         }
 389
 390         /*
 391          * Destroy all non-permission events. For permission events just
 392          * dequeue them and set the response. They will be freed once the
 393          * response is consumed and fanotify_get_response() returns.
 394          */
 395         while (!fsnotify_notify_queue_is_empty(group)) {
 396                 fsn_event = fsnotify_remove_first_event(group);
 397                 if (!(fsn_event->mask & FAN_ALL_PERM_EVENTS)) {
 398                         spin_unlock(&group->notification_lock);
 399                         fsnotify_destroy_event(group, fsn_event);
 400                         spin_lock(&group->notification_lock);
 401                 } else {
 402                         FANOTIFY_PE(fsn_event)->response = FAN_ALLOW;
 403                 }
 404         }
 405         spin_unlock(&group->notification_lock);
 406
 407         /* Response for all permission events it set, wakeup waiters */
 408         wake_up(&group->fanotify_data.access_waitq);
 409
 410         /* matches the fanotify_init->fsnotify_alloc_group */
 411         fsnotify_destroy_group(group);
 412
 413         return 0;
 414 }
 415
 416 static long fanotify_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 417 {
 418         struct fsnotify_group *group;
 419         struct fsnotify_event *fsn_event;
 420         void __user *p;
 421         int ret = -ENOTTY;
 422         size_t send_len = 0;
 423
 424         group = file->private_data;
 425
 426         p = (void __user *) arg;
 427
 428         switch (cmd) {
 429         case FIONREAD:
 430                 spin_lock(&group->notification_lock);
 431                 list_for_each_entry(fsn_event, &group->notification_list, list)
 432                         send_len += FAN_EVENT_METADATA_LEN;
 433                 spin_unlock(&group->notification_lock);
 434                 ret = put_user(send_len, (int __user *) p);
 435                 break;
 436         }
 437
 438         return ret;
 439 }
 440
 441 static const struct file_operations fanotify_fops = {
 442         .show_fdinfo    = fanotify_show_fdinfo,
 443         .poll           = fanotify_poll,
 444         .read           = fanotify_read,
 445         .write          = fanotify_write,
 446         .fasync         = NULL,
 447         .release        = fanotify_release,
 448         .unlocked_ioctl = fanotify_ioctl,
 449         .compat_ioctl   = fanotify_ioctl,
 450         .llseek         = noop_llseek,
 451 };
 452
 453 static int fanotify_find_path(int dfd, const char __user *filename,
 454                               struct path *path, unsigned int flags)
 455 {
 456         int ret;
 457
 458         pr_debug("%s: dfd=%d filename=%p flags=%x\n", __func__,
 459                  dfd, filename, flags);
 460
 461         if (filename == NULL) {
 462                 struct fd f = fdget(dfd);
 463
 464                 ret = -EBADF;
 465                 if (!f.file)
 466                         goto out;
 467
 468                 ret = -ENOTDIR;
 469                 if ((flags & FAN_MARK_ONLYDIR) &&
 470                     !(S_ISDIR(file_inode(f.file)->i_mode))) {
 471                         fdput(f);
 472                         goto out;
 473                 }
 474
 475                 *path = f.file->f_path;
 476                 path_get(path);
 477                 fdput(f);
 478         } else {
 479                 unsigned int lookup_flags = 0;
 480
 481                 if (!(flags & FAN_MARK_DONT_FOLLOW))
 482                         lookup_flags |= LOOKUP_FOLLOW;
 483                 if (flags & FAN_MARK_ONLYDIR)
 484                         lookup_flags |= LOOKUP_DIRECTORY;
 485
 486                 ret = user_path_at(dfd, filename, lookup_flags, path);
 487                 if (ret)
 488                         goto out;
 489         }
 490
 491         /* you can only watch an inode if you have read permissions on it */
 492         ret = inode_permission(path->dentry->d_inode, MAY_READ);
 493         if (ret)
 494                 path_put(path);
 495 out:
 496         return ret;
 497 }
 498
 499 static __u32 fanotify_mark_remove_from_mask(struct fsnotify_mark *fsn_mark,
 500                                             __u32 mask,
 501                                             unsigned int flags,
 502                                             int *destroy)
 503 {
 504         __u32 oldmask = 0;
 505
 506         spin_lock(&fsn_mark->lock);
 507         if (!(flags & FAN_MARK_IGNORED_MASK)) {
 508                 __u32 tmask = fsn_mark->mask & ~mask;
 509
 510                 if (flags & FAN_MARK_ONDIR)
 511                         tmask &= ~FAN_ONDIR;
 512
 513                 oldmask = fsn_mark->mask;
 514                 fsn_mark->mask = tmask;
 515         } else {
 516                 __u32 tmask = fsn_mark->ignored_mask & ~mask;
 517                 if (flags & FAN_MARK_ONDIR)
 518                         tmask &= ~FAN_ONDIR;
 519                 fsn_mark->ignored_mask = tmask;
 520         }
 521         *destroy = !(fsn_mark->mask | fsn_mark->ignored_mask);
 522         spin_unlock(&fsn_mark->lock);
 523
 524         return mask & oldmask;
 525 }
 526
 527 static int fanotify_remove_vfsmount_mark(struct fsnotify_group *group,
 528                                          struct vfsmount *mnt, __u32 mask,
 529                                          unsigned int flags)
 530 {
 531         struct fsnotify_mark *fsn_mark = NULL;
 532         __u32 removed;
 533         int destroy_mark;
 534
 535         mutex_lock(&group->mark_mutex);
 536         fsn_mark = fsnotify_find_mark(&real_mount(mnt)->mnt_fsnotify_marks,
 537                                       group);
 538         if (!fsn_mark) {
 539                 mutex_unlock(&group->mark_mutex);
 540                 return -ENOENT;
 541         }
 542
 543         removed = fanotify_mark_remove_from_mask(fsn_mark, mask, flags,
 544                                                  &destroy_mark);
 545         if (removed & real_mount(mnt)->mnt_fsnotify_mask)
 546                 fsnotify_recalc_mask(real_mount(mnt)->mnt_fsnotify_marks);
 547         if (destroy_mark)
 548                 fsnotify_detach_mark(fsn_mark);
 549         mutex_unlock(&group->mark_mutex);
 550         if (destroy_mark)
 551                 fsnotify_free_mark(fsn_mark);
 552
 553         fsnotify_put_mark(fsn_mark);
 554         return 0;
 555 }
 556
 557 static int fanotify_remove_inode_mark(struct fsnotify_group *group,
 558                                       struct inode *inode, __u32 mask,
 559                                       unsigned int flags)
 560 {
 561         struct fsnotify_mark *fsn_mark = NULL;
 562         __u32 removed;
 563         int destroy_mark;
 564
 565         mutex_lock(&group->mark_mutex);
 566         fsn_mark = fsnotify_find_mark(&inode->i_fsnotify_marks, group);
 567         if (!fsn_mark) {
 568                 mutex_unlock(&group->mark_mutex);
 569                 return -ENOENT;
 570         }
 571
 572         removed = fanotify_mark_remove_from_mask(fsn_mark, mask, flags,
 573                                                  &destroy_mark);
 574         if (removed & inode->i_fsnotify_mask)
 575                 fsnotify_recalc_mask(inode->i_fsnotify_marks);
 576         if (destroy_mark)
 577                 fsnotify_detach_mark(fsn_mark);
 578         mutex_unlock(&group->mark_mutex);
 579         if (destroy_mark)
 580                 fsnotify_free_mark(fsn_mark);
 581
 582         /* matches the fsnotify_find_mark() */
 583         fsnotify_put_mark(fsn_mark);
 584
 585         return 0;
 586 }
 587
 588 static __u32 fanotify_mark_add_to_mask(struct fsnotify_mark *fsn_mark,
 589                                        __u32 mask,
 590                                        unsigned int flags)
 591 {
 592         __u32 oldmask = -1;
 593
 594         spin_lock(&fsn_mark->lock);
 595         if (!(flags & FAN_MARK_IGNORED_MASK)) {
 596                 __u32 tmask = fsn_mark->mask | mask;
 597
 598                 if (flags & FAN_MARK_ONDIR)
 599                         tmask |= FAN_ONDIR;
 600
 601                 oldmask = fsn_mark->mask;
 602                 fsn_mark->mask = tmask;
 603         } else {
 604                 __u32 tmask = fsn_mark->ignored_mask | mask;
 605                 if (flags & FAN_MARK_ONDIR)
 606                         tmask |= FAN_ONDIR;
 607
 608                 fsn_mark->ignored_mask = tmask;
 609                 if (flags & FAN_MARK_IGNORED_SURV_MODIFY)
 610                         fsn_mark->flags |= FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY;
 611         }
 612         spin_unlock(&fsn_mark->lock);
 613
 614         return mask & ~oldmask;
 615 }
 616
 617 static struct fsnotify_mark *fanotify_add_new_mark(struct fsnotify_group *group,
 618                                                    struct inode *inode,
 619                                                    struct vfsmount *mnt)
 620 {
 621         struct fsnotify_mark *mark;
 622         int ret;
 623
 624         if (atomic_read(&group->num_marks) > group->fanotify_data.max_marks)
 625                 return ERR_PTR(-ENOSPC);
 626
 627         mark = kmem_cache_alloc(fanotify_mark_cache, GFP_KERNEL);
 628         if (!mark)
 629                 return ERR_PTR(-ENOMEM);
 630
 631         fsnotify_init_mark(mark, group);
 632         ret = fsnotify_add_mark_locked(mark, inode, mnt, 0);
 633         if (ret) {
 634                 fsnotify_put_mark(mark);
 635                 return ERR_PTR(ret);
 636         }
 637
 638         return mark;
 639 }
 640
 641
 642 static int fanotify_add_vfsmount_mark(struct fsnotify_group *group,
 643                                       struct vfsmount *mnt, __u32 mask,
 644                                       unsigned int flags)
 645 {
 646         struct fsnotify_mark *fsn_mark;
 647         __u32 added;
 648
 649         mutex_lock(&group->mark_mutex);
 650         fsn_mark = fsnotify_find_mark(&real_mount(mnt)->mnt_fsnotify_marks,
 651                                       group);
 652         if (!fsn_mark) {
 653                 fsn_mark = fanotify_add_new_mark(group, NULL, mnt);
 654                 if (IS_ERR(fsn_mark)) {
 655                         mutex_unlock(&group->mark_mutex);
 656                         return PTR_ERR(fsn_mark);
 657                 }
 658         }
 659         added = fanotify_mark_add_to_mask(fsn_mark, mask, flags);
 660         if (added & ~real_mount(mnt)->mnt_fsnotify_mask)
 661                 fsnotify_recalc_mask(real_mount(mnt)->mnt_fsnotify_marks);
 662         mutex_unlock(&group->mark_mutex);
 663
 664         fsnotify_put_mark(fsn_mark);
 665         return 0;
 666 }
 667
 668 static int fanotify_add_inode_mark(struct fsnotify_group *group,
 669                                    struct inode *inode, __u32 mask,
 670                                    unsigned int flags)
 671 {
 672         struct fsnotify_mark *fsn_mark;
 673         __u32 added;
 674
 675         pr_debug("%s: group=%p inode=%p\n", __func__, group, inode);
 676
 677         /*
 678          * If some other task has this inode open for write we should not add
 679          * an ignored mark, unless that ignored mark is supposed to survive
 680          * modification changes anyway.
 681          */
 682         if ((flags & FAN_MARK_IGNORED_MASK) &&
 683             !(flags & FAN_MARK_IGNORED_SURV_MODIFY) &&
 684             (atomic_read(&inode->i_writecount) > 0))
 685                 return 0;
 686
 687         mutex_lock(&group->mark_mutex);
 688         fsn_mark = fsnotify_find_mark(&inode->i_fsnotify_marks, group);
 689         if (!fsn_mark) {
 690                 fsn_mark = fanotify_add_new_mark(group, inode, NULL);
 691                 if (IS_ERR(fsn_mark)) {
 692                         mutex_unlock(&group->mark_mutex);
 693                         return PTR_ERR(fsn_mark);
 694                 }
 695         }
 696         added = fanotify_mark_add_to_mask(fsn_mark, mask, flags);
 697         if (added & ~inode->i_fsnotify_mask)
 698                 fsnotify_recalc_mask(inode->i_fsnotify_marks);
 699         mutex_unlock(&group->mark_mutex);
 700
 701         fsnotify_put_mark(fsn_mark);
 702         return 0;
 703 }
 704
 705 /* fanotify syscalls */
 706 SYSCALL_DEFINE2(fanotify_init, unsigned int, flags, unsigned int, event_f_flags)
 707 {
 708         struct fsnotify_group *group;
 709         int f_flags, fd;
 710         struct user_struct *user;
 711         struct fanotify_event_info *oevent;
 712
 713         pr_debug("%s: flags=%d event_f_flags=%d\n",
 714                 __func__, flags, event_f_flags);
 715
 716         if (!capable(CAP_SYS_ADMIN))
 717                 return -EPERM;
 718
 719 #ifdef CONFIG_AUDITSYSCALL
 720         if (flags & ~(FAN_ALL_INIT_FLAGS | FAN_ENABLE_AUDIT))
 721 #else
 722         if (flags & ~FAN_ALL_INIT_FLAGS)
 723 #endif
 724                 return -EINVAL;
 725
 726         if (event_f_flags & ~FANOTIFY_INIT_ALL_EVENT_F_BITS)
 727                 return -EINVAL;
 728
 729         switch (event_f_flags & O_ACCMODE) {
 730         case O_RDONLY:
 731         case O_RDWR:
 732         case O_WRONLY:
 733                 break;
 734         default:
 735                 return -EINVAL;
 736         }
 737
 738         user = get_current_user();
 739         if (atomic_read(&user->fanotify_listeners) > FANOTIFY_DEFAULT_MAX_LISTENERS) {
 740                 free_uid(user);
 741                 return -EMFILE;
 742         }
 743
 744         f_flags = O_RDWR | FMODE_NONOTIFY;
 745         if (flags & FAN_CLOEXEC)
 746                 f_flags |= O_CLOEXEC;
 747         if (flags & FAN_NONBLOCK)
 748                 f_flags |= O_NONBLOCK;
 749
 750         /* fsnotify_alloc_group takes a ref.  Dropped in fanotify_release */
 751         group = fsnotify_alloc_group(&fanotify_fsnotify_ops);
 752         if (IS_ERR(group)) {
 753                 free_uid(user);
 754                 return PTR_ERR(group);
 755         }
 756
 757         group->fanotify_data.user = user;
 758         atomic_inc(&user->fanotify_listeners);
 759
 760         oevent = fanotify_alloc_event(group, NULL, FS_Q_OVERFLOW, NULL);
 761         if (unlikely(!oevent)) {
 762                 fd = -ENOMEM;
 763                 goto out_destroy_group;
 764         }
 765         group->overflow_event = &oevent->fse;
 766
 767         if (force_o_largefile())
 768                 event_f_flags |= O_LARGEFILE;
 769         group->fanotify_data.f_flags = event_f_flags;
 770         init_waitqueue_head(&group->fanotify_data.access_waitq);
 771         INIT_LIST_HEAD(&group->fanotify_data.access_list);
 772         switch (flags & FAN_ALL_CLASS_BITS) {
 773         case FAN_CLASS_NOTIF:
 774                 group->priority = FS_PRIO_0;
 775                 break;
 776         case FAN_CLASS_CONTENT:
 777                 group->priority = FS_PRIO_1;
 778                 break;
 779         case FAN_CLASS_PRE_CONTENT:
 780                 group->priority = FS_PRIO_2;
 781                 break;
 782         default:
 783                 fd = -EINVAL;
 784                 goto out_destroy_group;
 785         }
 786
 787         if (flags & FAN_UNLIMITED_QUEUE) {
 788                 fd = -EPERM;
 789                 if (!capable(CAP_SYS_ADMIN))
 790                         goto out_destroy_group;
 791                 group->max_events = UINT_MAX;
 792         } else {
 793                 group->max_events = FANOTIFY_DEFAULT_MAX_EVENTS;
 794         }
 795
 796         if (flags & FAN_UNLIMITED_MARKS) {
 797                 fd = -EPERM;
 798                 if (!capable(CAP_SYS_ADMIN))
 799                         goto out_destroy_group;
 800                 group->fanotify_data.max_marks = UINT_MAX;
 801         } else {
 802                 group->fanotify_data.max_marks = FANOTIFY_DEFAULT_MAX_MARKS;
 803         }
 804
 805         if (flags & FAN_ENABLE_AUDIT) {
 806                 fd = -EPERM;
 807                 if (!capable(CAP_AUDIT_WRITE))
 808                         goto out_destroy_group;
 809                 group->fanotify_data.audit = true;
 810         }
 811
 812         fd = anon_inode_getfd("[fanotify]", &fanotify_fops, group, f_flags);
 813         if (fd < 0)
 814                 goto out_destroy_group;
 815
 816         return fd;
 817
 818 out_destroy_group:
 819         fsnotify_destroy_group(group);
 820         return fd;
 821 }
 822
 823 static int do_fanotify_mark(int fanotify_fd, unsigned int flags, __u64 mask,
 824                             int dfd, const char  __user *pathname)
 825 {
 826         struct inode *inode = NULL;
 827         struct vfsmount *mnt = NULL;
 828         struct fsnotify_group *group;
 829         struct fd f;
 830         struct path path;
 831         u32 valid_mask = FAN_ALL_EVENTS | FAN_EVENT_ON_CHILD;
 832         int ret;
 833
 834         pr_debug("%s: fanotify_fd=%d flags=%x dfd=%d pathname=%p mask=%llx\n",
 835                  __func__, fanotify_fd, flags, dfd, pathname, mask);
 836
 837         /* we only use the lower 32 bits as of right now. */
 838         if (mask & ((__u64)0xffffffff << 32))
 839                 return -EINVAL;
 840
 841         if (flags & ~FAN_ALL_MARK_FLAGS)
 842                 return -EINVAL;
 843         switch (flags & (FAN_MARK_ADD | FAN_MARK_REMOVE | FAN_MARK_FLUSH)) {
 844         case FAN_MARK_ADD:              /* fallthrough */
 845         case FAN_MARK_REMOVE:
 846                 if (!mask)
 847                         return -EINVAL;
 848                 break;
 849         case FAN_MARK_FLUSH:
 850                 if (flags & ~(FAN_MARK_MOUNT | FAN_MARK_FLUSH))
 851                         return -EINVAL;
 852                 break;
 853         default:
 854                 return -EINVAL;
 855         }
 856
 857         if (mask & FAN_ONDIR) {
 858                 flags |= FAN_MARK_ONDIR;
 859                 mask &= ~FAN_ONDIR;
 860         }
 861
 862         if (IS_ENABLED(CONFIG_FANOTIFY_ACCESS_PERMISSIONS))
 863                 valid_mask |= FAN_ALL_PERM_EVENTS;
 864
 865         if (mask & ~valid_mask)
 866                 return -EINVAL;
 867
 868         f = fdget(fanotify_fd);
 869         if (unlikely(!f.file))
 870                 return -EBADF;
 871
 872         /* verify that this is indeed an fanotify instance */
 873         ret = -EINVAL;
 874         if (unlikely(f.file->f_op != &fanotify_fops))
 875                 goto fput_and_out;
 876         group = f.file->private_data;
 877
 878         /*
 879          * group->priority == FS_PRIO_0 == FAN_CLASS_NOTIF.  These are not
 880          * allowed to set permissions events.
 881          */
 882         ret = -EINVAL;
 883         if (mask & FAN_ALL_PERM_EVENTS &&
 884             group->priority == FS_PRIO_0)
 885                 goto fput_and_out;
 886
 887         if (flags & FAN_MARK_FLUSH) {
 888                 ret = 0;
 889                 if (flags & FAN_MARK_MOUNT)
 890                         fsnotify_clear_vfsmount_marks_by_group(group);
 891                 else
 892                         fsnotify_clear_inode_marks_by_group(group);
 893                 goto fput_and_out;
 894         }
 895
 896         ret = fanotify_find_path(dfd, pathname, &path, flags);
 897         if (ret)
 898                 goto fput_and_out;
 899
 900         /* inode held in place by reference to path; group by fget on fd */
 901         if (!(flags & FAN_MARK_MOUNT))
 902                 inode = path.dentry->d_inode;
 903         else
 904                 mnt = path.mnt;
 905
 906         /* create/update an inode mark */
 907         switch (flags & (FAN_MARK_ADD | FAN_MARK_REMOVE)) {
 908         case FAN_MARK_ADD:
 909                 if (flags & FAN_MARK_MOUNT)
 910                         ret = fanotify_add_vfsmount_mark(group, mnt, mask, flags);
 911                 else
 912                         ret = fanotify_add_inode_mark(group, inode, mask, flags);
 913                 break;
 914         case FAN_MARK_REMOVE:
 915                 if (flags & FAN_MARK_MOUNT)
 916                         ret = fanotify_remove_vfsmount_mark(group, mnt, mask, flags);
 917                 else
 918                         ret = fanotify_remove_inode_mark(group, inode, mask, flags);
 919                 break;
 920         default:
 921                 ret = -EINVAL;
 922         }
 923
 924         path_put(&path);
 925 fput_and_out:
 926         fdput(f);
 927         return ret;
 928 }
 929
 930 SYSCALL_DEFINE5(fanotify_mark, int, fanotify_fd, unsigned int, flags,
 931                               __u64, mask, int, dfd,
 932                               const char  __user *, pathname)
 933 {
 934         return do_fanotify_mark(fanotify_fd, flags, mask, dfd, pathname);
 935 }
 936
 937 #ifdef CONFIG_COMPAT
 938 COMPAT_SYSCALL_DEFINE6(fanotify_mark,
 939                                 int, fanotify_fd, unsigned int, flags,
 940                                 __u32, mask0, __u32, mask1, int, dfd,
 941                                 const char  __user *, pathname)
 942 {
 943         return do_fanotify_mark(fanotify_fd, flags,
 944 #ifdef __BIG_ENDIAN
 945                                 ((__u64)mask0 << 32) | mask1,
 946 #else
 947                                 ((__u64)mask1 << 32) | mask0,
 948 #endif
 949                                  dfd, pathname);
 950 }
 951 #endif
 952
 953 /*
 954  * fanotify_user_setup - Our initialization function.  Note that we cannot return
 955  * error because we have compiled-in VFS hooks.  So an (unlikely) failure here
 956  * must result in panic().
 957  */
 958 static int __init fanotify_user_setup(void)
 959 {
 960         fanotify_mark_cache = KMEM_CACHE(fsnotify_mark, SLAB_PANIC);
 961         fanotify_event_cachep = KMEM_CACHE(fanotify_event_info, SLAB_PANIC);
 962         if (IS_ENABLED(CONFIG_FANOTIFY_ACCESS_PERMISSIONS)) {
 963                 fanotify_perm_event_cachep =
 964                         KMEM_CACHE(fanotify_perm_event_info, SLAB_PANIC);
 965         }
 966
 967         return 0;
 968 }
 969 device_initcall(fanotify_user_setup);