fs/notify/fanotify/fanotify_user.c

   1 #include <linux/fanotify.h>
   2 #include <linux/fcntl.h>
   3 #include <linux/file.h>
   4 #include <linux/fs.h>
   5 #include <linux/anon_inodes.h>
   6 #include <linux/fsnotify_backend.h>
   7 #include <linux/init.h>
   8 #include <linux/mount.h>
   9 #include <linux/namei.h>
  10 #include <linux/poll.h>
  11 #include <linux/security.h>
  12 #include <linux/syscalls.h>
  13 #include <linux/slab.h>
  14 #include <linux/types.h>
  15 #include <linux/uaccess.h>
  16 #include <linux/compat.h>
  17 #include <linux/sched/signal.h>
  18
  19 #include <asm/ioctls.h>
  20
  21 #include "../../mount.h"
  22 #include "../fdinfo.h"
  23 #include "fanotify.h"
  24
  25 #define FANOTIFY_DEFAULT_MAX_EVENTS     16384
  26 #define FANOTIFY_DEFAULT_MAX_MARKS      8192
  27 #define FANOTIFY_DEFAULT_MAX_LISTENERS  128
  28
  29 /*
  30  * All flags that may be specified in parameter event_f_flags of fanotify_init.
  31  *
  32  * Internal and external open flags are stored together in field f_flags of
  33  * struct file. Only external open flags shall be allowed in event_f_flags.
  34  * Internal flags like FMODE_NONOTIFY, FMODE_EXEC, FMODE_NOCMTIME shall be
  35  * excluded.
  36  */
  37 #define FANOTIFY_INIT_ALL_EVENT_F_BITS                          ( \
  38                 O_ACCMODE       | O_APPEND      | O_NONBLOCK    | \
  39                 __O_SYNC        | O_DSYNC       | O_CLOEXEC     | \
  40                 O_LARGEFILE     | O_NOATIME     )
  41
  42 extern const struct fsnotify_ops fanotify_fsnotify_ops;
  43
  44 struct kmem_cache *fanotify_mark_cache __read_mostly;
  45 struct kmem_cache *fanotify_event_cachep __read_mostly;
  46 struct kmem_cache *fanotify_perm_event_cachep __read_mostly;
  47
  48 /*
  49  * Get an fsnotify notification event if one exists and is small
  50  * enough to fit in "count". Return an error pointer if the count
  51  * is not large enough.
  52  *
  53  * Called with the group->notification_lock held.
  54  */
  55 static struct fsnotify_event *get_one_event(struct fsnotify_group *group,
  56                                             size_t count)
  57 {
  58         assert_spin_locked(&group->notification_lock);
  59
  60         pr_debug("%s: group=%p count=%zd\n", __func__, group, count);
  61
  62         if (fsnotify_notify_queue_is_empty(group))
  63                 return NULL;
  64
  65         if (FAN_EVENT_METADATA_LEN > count)
  66                 return ERR_PTR(-EINVAL);
  67
  68         /* held the notification_lock the whole time, so this is the
  69          * same event we peeked above */
  70         return fsnotify_remove_first_event(group);
  71 }
  72
  73 static int create_fd(struct fsnotify_group *group,
  74                      struct fanotify_event_info *event,
  75                      struct file **file)
  76 {
  77         int client_fd;
  78         struct file *new_file;
  79
  80         pr_debug("%s: group=%p event=%p\n", __func__, group, event);
  81
  82         client_fd = get_unused_fd_flags(group->fanotify_data.f_flags);
  83         if (client_fd < 0)
  84                 return client_fd;
  85
  86         /*
  87          * we need a new file handle for the userspace program so it can read even if it was
  88          * originally opened O_WRONLY.
  89          */
  90         /* it's possible this event was an overflow event.  in that case dentry and mnt
  91          * are NULL;  That's fine, just don't call dentry open */
  92         if (event->path.dentry && event->path.mnt)
  93                 new_file = dentry_open(&event->path,
  94                                        group->fanotify_data.f_flags | FMODE_NONOTIFY,
  95                                        current_cred());
  96         else
  97                 new_file = ERR_PTR(-EOVERFLOW);
  98         if (IS_ERR(new_file)) {
  99                 /*
 100                  * we still send an event even if we can't open the file.  this
 101                  * can happen when say tasks are gone and we try to open their
 102                  * /proc files or we try to open a WRONLY file like in sysfs
 103                  * we just send the errno to userspace since there isn't much
 104                  * else we can do.
 105                  */
 106                 put_unused_fd(client_fd);
 107                 client_fd = PTR_ERR(new_file);
 108         } else {
 109                 *file = new_file;
 110         }
 111
 112         return client_fd;
 113 }
 114
 115 static int fill_event_metadata(struct fsnotify_group *group,
 116                                struct fanotify_event_metadata *metadata,
 117                                struct fsnotify_event *fsn_event,
 118                                struct file **file)
 119 {
 120         int ret = 0;
 121         struct fanotify_event_info *event;
 122
 123         pr_debug("%s: group=%p metadata=%p event=%p\n", __func__,
 124                  group, metadata, fsn_event);
 125
 126         *file = NULL;
 127         event = container_of(fsn_event, struct fanotify_event_info, fse);
 128         metadata->event_len = FAN_EVENT_METADATA_LEN;
 129         metadata->metadata_len = FAN_EVENT_METADATA_LEN;
 130         metadata->vers = FANOTIFY_METADATA_VERSION;
 131         metadata->reserved = 0;
 132         metadata->mask = fsn_event->mask & FAN_ALL_OUTGOING_EVENTS;
 133         metadata->pid = pid_vnr(event->tgid);
 134         if (unlikely(fsn_event->mask & FAN_Q_OVERFLOW))
 135                 metadata->fd = FAN_NOFD;
 136         else {
 137                 metadata->fd = create_fd(group, event, file);
 138                 if (metadata->fd < 0)
 139                         ret = metadata->fd;
 140         }
 141
 142         return ret;
 143 }
 144
 145 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
 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) {
 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         event = dequeue_event(group, fd);
 194         if (!event)
 195                 return -ENOENT;
 196
 197         event->response = response;
 198         wake_up(&group->fanotify_data.access_waitq);
 199
 200         return 0;
 201 }
 202 #endif
 203
 204 static ssize_t copy_event_to_user(struct fsnotify_group *group,
 205                                   struct fsnotify_event *event,
 206                                   char __user *buf)
 207 {
 208         struct fanotify_event_metadata fanotify_event_metadata;
 209         struct file *f;
 210         int fd, ret;
 211
 212         pr_debug("%s: group=%p event=%p\n", __func__, group, event);
 213
 214         ret = fill_event_metadata(group, &fanotify_event_metadata, event, &f);
 215         if (ret < 0)
 216                 return ret;
 217
 218         fd = fanotify_event_metadata.fd;
 219         ret = -EFAULT;
 220         if (copy_to_user(buf, &fanotify_event_metadata,
 221                          fanotify_event_metadata.event_len))
 222                 goto out_close_fd;
 223
 224 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
 225         if (event->mask & FAN_ALL_PERM_EVENTS)
 226                 FANOTIFY_PE(event)->fd = fd;
 227 #endif
 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 unsigned int fanotify_poll(struct file *file, poll_table *wait)
 243 {
 244         struct fsnotify_group *group = file->private_data;
 245         int 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 = POLLIN | POLLRDNORM;
 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 (!(kevent->mask & FAN_ALL_PERM_EVENTS)) {
 313                         fsnotify_destroy_event(group, kevent);
 314                 } else {
 315 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
 316                         if (ret <= 0) {
 317                                 FANOTIFY_PE(kevent)->response = FAN_DENY;
 318                                 wake_up(&group->fanotify_data.access_waitq);
 319                         } else {
 320                                 spin_lock(&group->notification_lock);
 321                                 list_add_tail(&kevent->list,
 322                                         &group->fanotify_data.access_list);
 323                                 spin_unlock(&group->notification_lock);
 324                         }
 325 #endif
 326                 }
 327                 if (ret < 0)
 328                         break;
 329                 buf += ret;
 330                 count -= ret;
 331         }
 332         remove_wait_queue(&group->notification_waitq, &wait);
 333
 334         if (start != buf && ret != -EFAULT)
 335                 ret = buf - start;
 336         return ret;
 337 }
 338
 339 static ssize_t fanotify_write(struct file *file, const char __user *buf, size_t count, loff_t *pos)
 340 {
 341 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
 342         struct fanotify_response response = { .fd = -1, .response = -1 };
 343         struct fsnotify_group *group;
 344         int ret;
 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 #else
 362         return -EINVAL;
 363 #endif
 364 }
 365
 366 static int fanotify_release(struct inode *ignored, struct file *file)
 367 {
 368         struct fsnotify_group *group = file->private_data;
 369
 370 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
 371         struct fanotify_perm_event_info *event, *next;
 372         struct fsnotify_event *fsn_event;
 373
 374         /*
 375          * Stop new events from arriving in the notification queue. since
 376          * userspace cannot use fanotify fd anymore, no event can enter or
 377          * leave access_list by now either.
 378          */
 379         fsnotify_group_stop_queueing(group);
 380
 381         /*
 382          * Process all permission events on access_list and notification queue
 383          * and simulate reply from userspace.
 384          */
 385         spin_lock(&group->notification_lock);
 386         list_for_each_entry_safe(event, next, &group->fanotify_data.access_list,
 387                                  fae.fse.list) {
 388                 pr_debug("%s: found group=%p event=%p\n", __func__, group,
 389                          event);
 390
 391                 list_del_init(&event->fae.fse.list);
 392                 event->response = FAN_ALLOW;
 393         }
 394
 395         /*
 396          * Destroy all non-permission events. For permission events just
 397          * dequeue them and set the response. They will be freed once the
 398          * response is consumed and fanotify_get_response() returns.
 399          */
 400         while (!fsnotify_notify_queue_is_empty(group)) {
 401                 fsn_event = fsnotify_remove_first_event(group);
 402                 if (!(fsn_event->mask & FAN_ALL_PERM_EVENTS)) {
 403                         spin_unlock(&group->notification_lock);
 404                         fsnotify_destroy_event(group, fsn_event);
 405                         spin_lock(&group->notification_lock);
 406                 } else
 407                         FANOTIFY_PE(fsn_event)->response = FAN_ALLOW;
 408         }
 409         spin_unlock(&group->notification_lock);
 410
 411         /* Response for all permission events it set, wakeup waiters */
 412         wake_up(&group->fanotify_data.access_waitq);
 413 #endif
 414
 415         /* matches the fanotify_init->fsnotify_alloc_group */
 416         fsnotify_destroy_group(group);
 417
 418         return 0;
 419 }
 420
 421 static long fanotify_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 422 {
 423         struct fsnotify_group *group;
 424         struct fsnotify_event *fsn_event;
 425         void __user *p;
 426         int ret = -ENOTTY;
 427         size_t send_len = 0;
 428
 429         group = file->private_data;
 430
 431         p = (void __user *) arg;
 432
 433         switch (cmd) {
 434         case FIONREAD:
 435                 spin_lock(&group->notification_lock);
 436                 list_for_each_entry(fsn_event, &group->notification_list, list)
 437                         send_len += FAN_EVENT_METADATA_LEN;
 438                 spin_unlock(&group->notification_lock);
 439                 ret = put_user(send_len, (int __user *) p);
 440                 break;
 441         }
 442
 443         return ret;
 444 }
 445
 446 static const struct file_operations fanotify_fops = {
 447         .show_fdinfo    = fanotify_show_fdinfo,
 448         .poll           = fanotify_poll,
 449         .read           = fanotify_read,
 450         .write          = fanotify_write,
 451         .fasync         = NULL,
 452         .release        = fanotify_release,
 453         .unlocked_ioctl = fanotify_ioctl,
 454         .compat_ioctl   = fanotify_ioctl,
 455         .llseek         = noop_llseek,
 456 };
 457
 458 static int fanotify_find_path(int dfd, const char __user *filename,
 459                               struct path *path, unsigned int flags)
 460 {
 461         int ret;
 462
 463         pr_debug("%s: dfd=%d filename=%p flags=%x\n", __func__,
 464                  dfd, filename, flags);
 465
 466         if (filename == NULL) {
 467                 struct fd f = fdget(dfd);
 468
 469                 ret = -EBADF;
 470                 if (!f.file)
 471                         goto out;
 472
 473                 ret = -ENOTDIR;
 474                 if ((flags & FAN_MARK_ONLYDIR) &&
 475                     !(S_ISDIR(file_inode(f.file)->i_mode))) {
 476                         fdput(f);
 477                         goto out;
 478                 }
 479
 480                 *path = f.file->f_path;
 481                 path_get(path);
 482                 fdput(f);
 483         } else {
 484                 unsigned int lookup_flags = 0;
 485
 486                 if (!(flags & FAN_MARK_DONT_FOLLOW))
 487                         lookup_flags |= LOOKUP_FOLLOW;
 488                 if (flags & FAN_MARK_ONLYDIR)
 489                         lookup_flags |= LOOKUP_DIRECTORY;
 490
 491                 ret = user_path_at(dfd, filename, lookup_flags, path);
 492                 if (ret)
 493                         goto out;
 494         }
 495
 496         /* you can only watch an inode if you have read permissions on it */
 497         ret = inode_permission(path->dentry->d_inode, MAY_READ);
 498         if (ret)
 499                 path_put(path);
 500 out:
 501         return ret;
 502 }
 503
 504 static __u32 fanotify_mark_remove_from_mask(struct fsnotify_mark *fsn_mark,
 505                                             __u32 mask,
 506                                             unsigned int flags,
 507                                             int *destroy)
 508 {
 509         __u32 oldmask = 0;
 510
 511         spin_lock(&fsn_mark->lock);
 512         if (!(flags & FAN_MARK_IGNORED_MASK)) {
 513                 __u32 tmask = fsn_mark->mask & ~mask;
 514
 515                 if (flags & FAN_MARK_ONDIR)
 516                         tmask &= ~FAN_ONDIR;
 517
 518                 oldmask = fsn_mark->mask;
 519                 fsn_mark->mask = tmask;
 520         } else {
 521                 __u32 tmask = fsn_mark->ignored_mask & ~mask;
 522                 if (flags & FAN_MARK_ONDIR)
 523                         tmask &= ~FAN_ONDIR;
 524                 fsn_mark->ignored_mask = tmask;
 525         }
 526         *destroy = !(fsn_mark->mask | fsn_mark->ignored_mask);
 527         spin_unlock(&fsn_mark->lock);
 528
 529         return mask & oldmask;
 530 }
 531
 532 static int fanotify_remove_vfsmount_mark(struct fsnotify_group *group,
 533                                          struct vfsmount *mnt, __u32 mask,
 534                                          unsigned int flags)
 535 {
 536         struct fsnotify_mark *fsn_mark = NULL;
 537         __u32 removed;
 538         int destroy_mark;
 539
 540         mutex_lock(&group->mark_mutex);
 541         fsn_mark = fsnotify_find_mark(&real_mount(mnt)->mnt_fsnotify_marks,
 542                                       group);
 543         if (!fsn_mark) {
 544                 mutex_unlock(&group->mark_mutex);
 545                 return -ENOENT;
 546         }
 547
 548         removed = fanotify_mark_remove_from_mask(fsn_mark, mask, flags,
 549                                                  &destroy_mark);
 550         if (removed & real_mount(mnt)->mnt_fsnotify_mask)
 551                 fsnotify_recalc_mask(real_mount(mnt)->mnt_fsnotify_marks);
 552         if (destroy_mark)
 553                 fsnotify_detach_mark(fsn_mark);
 554         mutex_unlock(&group->mark_mutex);
 555         if (destroy_mark)
 556                 fsnotify_free_mark(fsn_mark);
 557
 558         fsnotify_put_mark(fsn_mark);
 559         return 0;
 560 }
 561
 562 static int fanotify_remove_inode_mark(struct fsnotify_group *group,
 563                                       struct inode *inode, __u32 mask,
 564                                       unsigned int flags)
 565 {
 566         struct fsnotify_mark *fsn_mark = NULL;
 567         __u32 removed;
 568         int destroy_mark;
 569
 570         mutex_lock(&group->mark_mutex);
 571         fsn_mark = fsnotify_find_mark(&inode->i_fsnotify_marks, group);
 572         if (!fsn_mark) {
 573                 mutex_unlock(&group->mark_mutex);
 574                 return -ENOENT;
 575         }
 576
 577         removed = fanotify_mark_remove_from_mask(fsn_mark, mask, flags,
 578                                                  &destroy_mark);
 579         if (removed & inode->i_fsnotify_mask)
 580                 fsnotify_recalc_mask(inode->i_fsnotify_marks);
 581         if (destroy_mark)
 582                 fsnotify_detach_mark(fsn_mark);
 583         mutex_unlock(&group->mark_mutex);
 584         if (destroy_mark)
 585                 fsnotify_free_mark(fsn_mark);
 586
 587         /* matches the fsnotify_find_mark() */
 588         fsnotify_put_mark(fsn_mark);
 589
 590         return 0;
 591 }
 592
 593 static __u32 fanotify_mark_add_to_mask(struct fsnotify_mark *fsn_mark,
 594                                        __u32 mask,
 595                                        unsigned int flags)
 596 {
 597         __u32 oldmask = -1;
 598
 599         spin_lock(&fsn_mark->lock);
 600         if (!(flags & FAN_MARK_IGNORED_MASK)) {
 601                 __u32 tmask = fsn_mark->mask | mask;
 602
 603                 if (flags & FAN_MARK_ONDIR)
 604                         tmask |= FAN_ONDIR;
 605
 606                 oldmask = fsn_mark->mask;
 607                 fsn_mark->mask = tmask;
 608         } else {
 609                 __u32 tmask = fsn_mark->ignored_mask | mask;
 610                 if (flags & FAN_MARK_ONDIR)
 611                         tmask |= FAN_ONDIR;
 612
 613                 fsn_mark->ignored_mask = tmask;
 614                 if (flags & FAN_MARK_IGNORED_SURV_MODIFY)
 615                         fsn_mark->flags |= FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY;
 616         }
 617         spin_unlock(&fsn_mark->lock);
 618
 619         return mask & ~oldmask;
 620 }
 621
 622 static struct fsnotify_mark *fanotify_add_new_mark(struct fsnotify_group *group,
 623                                                    struct inode *inode,
 624                                                    struct vfsmount *mnt)
 625 {
 626         struct fsnotify_mark *mark;
 627         int ret;
 628
 629         if (atomic_read(&group->num_marks) > group->fanotify_data.max_marks)
 630                 return ERR_PTR(-ENOSPC);
 631
 632         mark = kmem_cache_alloc(fanotify_mark_cache, GFP_KERNEL);
 633         if (!mark)
 634                 return ERR_PTR(-ENOMEM);
 635
 636         fsnotify_init_mark(mark, group);
 637         ret = fsnotify_add_mark_locked(mark, inode, mnt, 0);
 638         if (ret) {
 639                 fsnotify_put_mark(mark);
 640                 return ERR_PTR(ret);
 641         }
 642
 643         return mark;
 644 }
 645
 646
 647 static int fanotify_add_vfsmount_mark(struct fsnotify_group *group,
 648                                       struct vfsmount *mnt, __u32 mask,
 649                                       unsigned int flags)
 650 {
 651         struct fsnotify_mark *fsn_mark;
 652         __u32 added;
 653
 654         mutex_lock(&group->mark_mutex);
 655         fsn_mark = fsnotify_find_mark(&real_mount(mnt)->mnt_fsnotify_marks,
 656                                       group);
 657         if (!fsn_mark) {
 658                 fsn_mark = fanotify_add_new_mark(group, NULL, mnt);
 659                 if (IS_ERR(fsn_mark)) {
 660                         mutex_unlock(&group->mark_mutex);
 661                         return PTR_ERR(fsn_mark);
 662                 }
 663         }
 664         added = fanotify_mark_add_to_mask(fsn_mark, mask, flags);
 665         if (added & ~real_mount(mnt)->mnt_fsnotify_mask)
 666                 fsnotify_recalc_mask(real_mount(mnt)->mnt_fsnotify_marks);
 667         mutex_unlock(&group->mark_mutex);
 668
 669         fsnotify_put_mark(fsn_mark);
 670         return 0;
 671 }
 672
 673 static int fanotify_add_inode_mark(struct fsnotify_group *group,
 674                                    struct inode *inode, __u32 mask,
 675                                    unsigned int flags)
 676 {
 677         struct fsnotify_mark *fsn_mark;
 678         __u32 added;
 679
 680         pr_debug("%s: group=%p inode=%p\n", __func__, group, inode);
 681
 682         /*
 683          * If some other task has this inode open for write we should not add
 684          * an ignored mark, unless that ignored mark is supposed to survive
 685          * modification changes anyway.
 686          */
 687         if ((flags & FAN_MARK_IGNORED_MASK) &&
 688             !(flags & FAN_MARK_IGNORED_SURV_MODIFY) &&
 689             (atomic_read(&inode->i_writecount) > 0))
 690                 return 0;
 691
 692         mutex_lock(&group->mark_mutex);
 693         fsn_mark = fsnotify_find_mark(&inode->i_fsnotify_marks, group);
 694         if (!fsn_mark) {
 695                 fsn_mark = fanotify_add_new_mark(group, inode, NULL);
 696                 if (IS_ERR(fsn_mark)) {
 697                         mutex_unlock(&group->mark_mutex);
 698                         return PTR_ERR(fsn_mark);
 699                 }
 700         }
 701         added = fanotify_mark_add_to_mask(fsn_mark, mask, flags);
 702         if (added & ~inode->i_fsnotify_mask)
 703                 fsnotify_recalc_mask(inode->i_fsnotify_marks);
 704         mutex_unlock(&group->mark_mutex);
 705
 706         fsnotify_put_mark(fsn_mark);
 707         return 0;
 708 }
 709
 710 /* fanotify syscalls */
 711 SYSCALL_DEFINE2(fanotify_init, unsigned int, flags, unsigned int, event_f_flags)
 712 {
 713         struct fsnotify_group *group;
 714         int f_flags, fd;
 715         struct user_struct *user;
 716         struct fanotify_event_info *oevent;
 717
 718         pr_debug("%s: flags=%d event_f_flags=%d\n",
 719                 __func__, flags, event_f_flags);
 720
 721         if (!capable(CAP_SYS_ADMIN))
 722                 return -EPERM;
 723
 724         if (flags & ~FAN_ALL_INIT_FLAGS)
 725                 return -EINVAL;
 726
 727         if (event_f_flags & ~FANOTIFY_INIT_ALL_EVENT_F_BITS)
 728                 return -EINVAL;
 729
 730         switch (event_f_flags & O_ACCMODE) {
 731         case O_RDONLY:
 732         case O_RDWR:
 733         case O_WRONLY:
 734                 break;
 735         default:
 736                 return -EINVAL;
 737         }
 738
 739         user = get_current_user();
 740         if (atomic_read(&user->fanotify_listeners) > FANOTIFY_DEFAULT_MAX_LISTENERS) {
 741                 free_uid(user);
 742                 return -EMFILE;
 743         }
 744
 745         f_flags = O_RDWR | FMODE_NONOTIFY;
 746         if (flags & FAN_CLOEXEC)
 747                 f_flags |= O_CLOEXEC;
 748         if (flags & FAN_NONBLOCK)
 749                 f_flags |= O_NONBLOCK;
 750
 751         /* fsnotify_alloc_group takes a ref.  Dropped in fanotify_release */
 752         group = fsnotify_alloc_group(&fanotify_fsnotify_ops);
 753         if (IS_ERR(group)) {
 754                 free_uid(user);
 755                 return PTR_ERR(group);
 756         }
 757
 758         group->fanotify_data.user = user;
 759         atomic_inc(&user->fanotify_listeners);
 760
 761         oevent = fanotify_alloc_event(NULL, FS_Q_OVERFLOW, NULL);
 762         if (unlikely(!oevent)) {
 763                 fd = -ENOMEM;
 764                 goto out_destroy_group;
 765         }
 766         group->overflow_event = &oevent->fse;
 767
 768         if (force_o_largefile())
 769                 event_f_flags |= O_LARGEFILE;
 770         group->fanotify_data.f_flags = event_f_flags;
 771 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
 772         init_waitqueue_head(&group->fanotify_data.access_waitq);
 773         INIT_LIST_HEAD(&group->fanotify_data.access_list);
 774 #endif
 775         switch (flags & FAN_ALL_CLASS_BITS) {
 776         case FAN_CLASS_NOTIF:
 777                 group->priority = FS_PRIO_0;
 778                 break;
 779         case FAN_CLASS_CONTENT:
 780                 group->priority = FS_PRIO_1;
 781                 break;
 782         case FAN_CLASS_PRE_CONTENT:
 783                 group->priority = FS_PRIO_2;
 784                 break;
 785         default:
 786                 fd = -EINVAL;
 787                 goto out_destroy_group;
 788         }
 789
 790         if (flags & FAN_UNLIMITED_QUEUE) {
 791                 fd = -EPERM;
 792                 if (!capable(CAP_SYS_ADMIN))
 793                         goto out_destroy_group;
 794                 group->max_events = UINT_MAX;
 795         } else {
 796                 group->max_events = FANOTIFY_DEFAULT_MAX_EVENTS;
 797         }
 798
 799         if (flags & FAN_UNLIMITED_MARKS) {
 800                 fd = -EPERM;
 801                 if (!capable(CAP_SYS_ADMIN))
 802                         goto out_destroy_group;
 803                 group->fanotify_data.max_marks = UINT_MAX;
 804         } else {
 805                 group->fanotify_data.max_marks = FANOTIFY_DEFAULT_MAX_MARKS;
 806         }
 807
 808         fd = anon_inode_getfd("[fanotify]", &fanotify_fops, group, f_flags);
 809         if (fd < 0)
 810                 goto out_destroy_group;
 811
 812         return fd;
 813
 814 out_destroy_group:
 815         fsnotify_destroy_group(group);
 816         return fd;
 817 }
 818
 819 SYSCALL_DEFINE5(fanotify_mark, int, fanotify_fd, unsigned int, flags,
 820                               __u64, mask, int, dfd,
 821                               const char  __user *, pathname)
 822 {
 823         struct inode *inode = NULL;
 824         struct vfsmount *mnt = NULL;
 825         struct fsnotify_group *group;
 826         struct fd f;
 827         struct path path;
 828         int ret;
 829
 830         pr_debug("%s: fanotify_fd=%d flags=%x dfd=%d pathname=%p mask=%llx\n",
 831                  __func__, fanotify_fd, flags, dfd, pathname, mask);
 832
 833         /* we only use the lower 32 bits as of right now. */
 834         if (mask & ((__u64)0xffffffff << 32))
 835                 return -EINVAL;
 836
 837         if (flags & ~FAN_ALL_MARK_FLAGS)
 838                 return -EINVAL;
 839         switch (flags & (FAN_MARK_ADD | FAN_MARK_REMOVE | FAN_MARK_FLUSH)) {
 840         case FAN_MARK_ADD:              /* fallthrough */
 841         case FAN_MARK_REMOVE:
 842                 if (!mask)
 843                         return -EINVAL;
 844                 break;
 845         case FAN_MARK_FLUSH:
 846                 if (flags & ~(FAN_MARK_MOUNT | FAN_MARK_FLUSH))
 847                         return -EINVAL;
 848                 break;
 849         default:
 850                 return -EINVAL;
 851         }
 852
 853         if (mask & FAN_ONDIR) {
 854                 flags |= FAN_MARK_ONDIR;
 855                 mask &= ~FAN_ONDIR;
 856         }
 857
 858 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
 859         if (mask & ~(FAN_ALL_EVENTS | FAN_ALL_PERM_EVENTS | FAN_EVENT_ON_CHILD))
 860 #else
 861         if (mask & ~(FAN_ALL_EVENTS | FAN_EVENT_ON_CHILD))
 862 #endif
 863                 return -EINVAL;
 864
 865         f = fdget(fanotify_fd);
 866         if (unlikely(!f.file))
 867                 return -EBADF;
 868
 869         /* verify that this is indeed an fanotify instance */
 870         ret = -EINVAL;
 871         if (unlikely(f.file->f_op != &fanotify_fops))
 872                 goto fput_and_out;
 873         group = f.file->private_data;
 874
 875         /*
 876          * group->priority == FS_PRIO_0 == FAN_CLASS_NOTIF.  These are not
 877          * allowed to set permissions events.
 878          */
 879         ret = -EINVAL;
 880         if (mask & FAN_ALL_PERM_EVENTS &&
 881             group->priority == FS_PRIO_0)
 882                 goto fput_and_out;
 883
 884         if (flags & FAN_MARK_FLUSH) {
 885                 ret = 0;
 886                 if (flags & FAN_MARK_MOUNT)
 887                         fsnotify_clear_vfsmount_marks_by_group(group);
 888                 else
 889                         fsnotify_clear_inode_marks_by_group(group);
 890                 goto fput_and_out;
 891         }
 892
 893         ret = fanotify_find_path(dfd, pathname, &path, flags);
 894         if (ret)
 895                 goto fput_and_out;
 896
 897         /* inode held in place by reference to path; group by fget on fd */
 898         if (!(flags & FAN_MARK_MOUNT))
 899                 inode = path.dentry->d_inode;
 900         else
 901                 mnt = path.mnt;
 902
 903         /* create/update an inode mark */
 904         switch (flags & (FAN_MARK_ADD | FAN_MARK_REMOVE)) {
 905         case FAN_MARK_ADD:
 906                 if (flags & FAN_MARK_MOUNT)
 907                         ret = fanotify_add_vfsmount_mark(group, mnt, mask, flags);
 908                 else
 909                         ret = fanotify_add_inode_mark(group, inode, mask, flags);
 910                 break;
 911         case FAN_MARK_REMOVE:
 912                 if (flags & FAN_MARK_MOUNT)
 913                         ret = fanotify_remove_vfsmount_mark(group, mnt, mask, flags);
 914                 else
 915                         ret = fanotify_remove_inode_mark(group, inode, mask, flags);
 916                 break;
 917         default:
 918                 ret = -EINVAL;
 919         }
 920
 921         path_put(&path);
 922 fput_and_out:
 923         fdput(f);
 924         return ret;
 925 }
 926
 927 #ifdef CONFIG_COMPAT
 928 COMPAT_SYSCALL_DEFINE6(fanotify_mark,
 929                                 int, fanotify_fd, unsigned int, flags,
 930                                 __u32, mask0, __u32, mask1, int, dfd,
 931                                 const char  __user *, pathname)
 932 {
 933         return sys_fanotify_mark(fanotify_fd, flags,
 934 #ifdef __BIG_ENDIAN
 935                                 ((__u64)mask0 << 32) | mask1,
 936 #else
 937                                 ((__u64)mask1 << 32) | mask0,
 938 #endif
 939                                  dfd, pathname);
 940 }
 941 #endif
 942
 943 /*
 944  * fanotify_user_setup - Our initialization function.  Note that we cannot return
 945  * error because we have compiled-in VFS hooks.  So an (unlikely) failure here
 946  * must result in panic().
 947  */
 948 static int __init fanotify_user_setup(void)
 949 {
 950         fanotify_mark_cache = KMEM_CACHE(fsnotify_mark, SLAB_PANIC);
 951         fanotify_event_cachep = KMEM_CACHE(fanotify_event_info, SLAB_PANIC);
 952 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
 953         fanotify_perm_event_cachep = KMEM_CACHE(fanotify_perm_event_info,
 954                                                 SLAB_PANIC);
 955 #endif
 956
 957         return 0;
 958 }
 959 device_initcall(fanotify_user_setup);