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
  18 #include <asm/ioctls.h>
  19
  20 #include "../../mount.h"
  21 #include "../fdinfo.h"
  22
  23 #define FANOTIFY_DEFAULT_MAX_EVENTS     16384
  24 #define FANOTIFY_DEFAULT_MAX_MARKS      8192
  25 #define FANOTIFY_DEFAULT_MAX_LISTENERS  128
  26
  27 extern const struct fsnotify_ops fanotify_fsnotify_ops;
  28
  29 static struct kmem_cache *fanotify_mark_cache __read_mostly;
  30 static struct kmem_cache *fanotify_response_event_cache __read_mostly;
  31
  32 struct fanotify_response_event {
  33         struct list_head list;
  34         __s32 fd;
  35         struct fsnotify_event *event;
  36 };
  37
  38 /*
  39  * Get an fsnotify notification event if one exists and is small
  40  * enough to fit in "count". Return an error pointer if the count
  41  * is not large enough.
  42  *
  43  * Called with the group->notification_mutex held.
  44  */
  45 static struct fsnotify_event *get_one_event(struct fsnotify_group *group,
  46                                             size_t count)
  47 {
  48         BUG_ON(!mutex_is_locked(&group->notification_mutex));
  49
  50         pr_debug("%s: group=%p count=%zd\n", __func__, group, count);
  51
  52         if (fsnotify_notify_queue_is_empty(group))
  53                 return NULL;
  54
  55         if (FAN_EVENT_METADATA_LEN > count)
  56                 return ERR_PTR(-EINVAL);
  57
  58         /* held the notification_mutex the whole time, so this is the
  59          * same event we peeked above */
  60         return fsnotify_remove_notify_event(group);
  61 }
  62
  63 static int create_fd(struct fsnotify_group *group,
  64                         struct fsnotify_event *event,
  65                         struct file **file)
  66 {
  67         int client_fd;
  68         struct file *new_file;
  69
  70         pr_debug("%s: group=%p event=%p\n", __func__, group, event);
  71
  72         client_fd = get_unused_fd_flags(group->fanotify_data.f_flags);
  73         if (client_fd < 0)
  74                 return client_fd;
  75
  76         if (event->data_type != FSNOTIFY_EVENT_PATH) {
  77                 WARN_ON(1);
  78                 put_unused_fd(client_fd);
  79                 return -EINVAL;
  80         }
  81
  82         /*
  83          * we need a new file handle for the userspace program so it can read even if it was
  84          * originally opened O_WRONLY.
  85          */
  86         /* it's possible this event was an overflow event.  in that case dentry and mnt
  87          * are NULL;  That's fine, just don't call dentry open */
  88         if (event->path.dentry && event->path.mnt)
  89                 new_file = dentry_open(&event->path,
  90                                        group->fanotify_data.f_flags | FMODE_NONOTIFY,
  91                                        current_cred());
  92         else
  93                 new_file = ERR_PTR(-EOVERFLOW);
  94         if (IS_ERR(new_file)) {
  95                 /*
  96                  * we still send an event even if we can't open the file.  this
  97                  * can happen when say tasks are gone and we try to open their
  98                  * /proc files or we try to open a WRONLY file like in sysfs
  99                  * we just send the errno to userspace since there isn't much
 100                  * else we can do.
 101                  */
 102                 put_unused_fd(client_fd);
 103                 client_fd = PTR_ERR(new_file);
 104         } else {
 105                 *file = new_file;
 106         }
 107
 108         return client_fd;
 109 }
 110
 111 static int fill_event_metadata(struct fsnotify_group *group,
 112                                    struct fanotify_event_metadata *metadata,
 113                                    struct fsnotify_event *event,
 114                                    struct file **file)
 115 {
 116         int ret = 0;
 117
 118         pr_debug("%s: group=%p metadata=%p event=%p\n", __func__,
 119                  group, metadata, event);
 120
 121         *file = NULL;
 122         metadata->event_len = FAN_EVENT_METADATA_LEN;
 123         metadata->metadata_len = FAN_EVENT_METADATA_LEN;
 124         metadata->vers = FANOTIFY_METADATA_VERSION;
 125         metadata->reserved = 0;
 126         metadata->mask = event->mask & FAN_ALL_OUTGOING_EVENTS;
 127         metadata->pid = pid_vnr(event->tgid);
 128         if (unlikely(event->mask & FAN_Q_OVERFLOW))
 129                 metadata->fd = FAN_NOFD;
 130         else {
 131                 metadata->fd = create_fd(group, event, file);
 132                 if (metadata->fd < 0)
 133                         ret = metadata->fd;
 134         }
 135
 136         return ret;
 137 }
 138
 139 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
 140 static struct fanotify_response_event *dequeue_re(struct fsnotify_group *group,
 141                                                   __s32 fd)
 142 {
 143         struct fanotify_response_event *re, *return_re = NULL;
 144
 145         mutex_lock(&group->fanotify_data.access_mutex);
 146         list_for_each_entry(re, &group->fanotify_data.access_list, list) {
 147                 if (re->fd != fd)
 148                         continue;
 149
 150                 list_del_init(&re->list);
 151                 return_re = re;
 152                 break;
 153         }
 154         mutex_unlock(&group->fanotify_data.access_mutex);
 155
 156         pr_debug("%s: found return_re=%p\n", __func__, return_re);
 157
 158         return return_re;
 159 }
 160
 161 static int process_access_response(struct fsnotify_group *group,
 162                                    struct fanotify_response *response_struct)
 163 {
 164         struct fanotify_response_event *re;
 165         __s32 fd = response_struct->fd;
 166         __u32 response = response_struct->response;
 167
 168         pr_debug("%s: group=%p fd=%d response=%d\n", __func__, group,
 169                  fd, response);
 170         /*
 171          * make sure the response is valid, if invalid we do nothing and either
 172          * userspace can send a valid response or we will clean it up after the
 173          * timeout
 174          */
 175         switch (response) {
 176         case FAN_ALLOW:
 177         case FAN_DENY:
 178                 break;
 179         default:
 180                 return -EINVAL;
 181         }
 182
 183         if (fd < 0)
 184                 return -EINVAL;
 185
 186         re = dequeue_re(group, fd);
 187         if (!re)
 188                 return -ENOENT;
 189
 190         re->event->response = response;
 191
 192         wake_up(&group->fanotify_data.access_waitq);
 193
 194         kmem_cache_free(fanotify_response_event_cache, re);
 195
 196         return 0;
 197 }
 198
 199 static int prepare_for_access_response(struct fsnotify_group *group,
 200                                        struct fsnotify_event *event,
 201                                        __s32 fd)
 202 {
 203         struct fanotify_response_event *re;
 204
 205         if (!(event->mask & FAN_ALL_PERM_EVENTS))
 206                 return 0;
 207
 208         re = kmem_cache_alloc(fanotify_response_event_cache, GFP_KERNEL);
 209         if (!re)
 210                 return -ENOMEM;
 211
 212         re->event = event;
 213         re->fd = fd;
 214
 215         mutex_lock(&group->fanotify_data.access_mutex);
 216
 217         if (atomic_read(&group->fanotify_data.bypass_perm)) {
 218                 mutex_unlock(&group->fanotify_data.access_mutex);
 219                 kmem_cache_free(fanotify_response_event_cache, re);
 220                 event->response = FAN_ALLOW;
 221                 return 0;
 222         }
 223
 224         list_add_tail(&re->list, &group->fanotify_data.access_list);
 225         mutex_unlock(&group->fanotify_data.access_mutex);
 226
 227         return 0;
 228 }
 229
 230 #else
 231 static int prepare_for_access_response(struct fsnotify_group *group,
 232                                        struct fsnotify_event *event,
 233                                        __s32 fd)
 234 {
 235         return 0;
 236 }
 237
 238 #endif
 239
 240 static ssize_t copy_event_to_user(struct fsnotify_group *group,
 241                                   struct fsnotify_event *event,
 242                                   char __user *buf)
 243 {
 244         struct fanotify_event_metadata fanotify_event_metadata;
 245         struct file *f;
 246         int fd, ret;
 247
 248         pr_debug("%s: group=%p event=%p\n", __func__, group, event);
 249
 250         ret = fill_event_metadata(group, &fanotify_event_metadata, event, &f);
 251         if (ret < 0)
 252                 goto out;
 253
 254         fd = fanotify_event_metadata.fd;
 255         ret = -EFAULT;
 256         if (copy_to_user(buf, &fanotify_event_metadata,
 257                          fanotify_event_metadata.event_len))
 258                 goto out_close_fd;
 259
 260         ret = prepare_for_access_response(group, event, fd);
 261         if (ret)
 262                 goto out_close_fd;
 263
 264         if (fd != FAN_NOFD)
 265                 fd_install(fd, f);
 266         return fanotify_event_metadata.event_len;
 267
 268 out_close_fd:
 269         if (fd != FAN_NOFD) {
 270                 put_unused_fd(fd);
 271                 fput(f);
 272         }
 273 out:
 274 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
 275         if (event->mask & FAN_ALL_PERM_EVENTS) {
 276                 event->response = FAN_DENY;
 277                 wake_up(&group->fanotify_data.access_waitq);
 278         }
 279 #endif
 280         return ret;
 281 }
 282
 283 /* intofiy userspace file descriptor functions */
 284 static unsigned int fanotify_poll(struct file *file, poll_table *wait)
 285 {
 286         struct fsnotify_group *group = file->private_data;
 287         int ret = 0;
 288
 289         poll_wait(file, &group->notification_waitq, wait);
 290         mutex_lock(&group->notification_mutex);
 291         if (!fsnotify_notify_queue_is_empty(group))
 292                 ret = POLLIN | POLLRDNORM;
 293         mutex_unlock(&group->notification_mutex);
 294
 295         return ret;
 296 }
 297
 298 static ssize_t fanotify_read(struct file *file, char __user *buf,
 299                              size_t count, loff_t *pos)
 300 {
 301         struct fsnotify_group *group;
 302         struct fsnotify_event *kevent;
 303         char __user *start;
 304         int ret;
 305         DEFINE_WAIT(wait);
 306
 307         start = buf;
 308         group = file->private_data;
 309
 310         pr_debug("%s: group=%p\n", __func__, group);
 311
 312         while (1) {
 313                 prepare_to_wait(&group->notification_waitq, &wait, TASK_INTERRUPTIBLE);
 314
 315                 mutex_lock(&group->notification_mutex);
 316                 kevent = get_one_event(group, count);
 317                 mutex_unlock(&group->notification_mutex);
 318
 319                 if (kevent) {
 320                         ret = PTR_ERR(kevent);
 321                         if (IS_ERR(kevent))
 322                                 break;
 323                         ret = copy_event_to_user(group, kevent, buf);
 324                         fsnotify_put_event(kevent);
 325                         if (ret < 0)
 326                                 break;
 327                         buf += ret;
 328                         count -= ret;
 329                         continue;
 330                 }
 331
 332                 ret = -EAGAIN;
 333                 if (file->f_flags & O_NONBLOCK)
 334                         break;
 335                 ret = -ERESTARTSYS;
 336                 if (signal_pending(current))
 337                         break;
 338
 339                 if (start != buf)
 340                         break;
 341
 342                 schedule();
 343         }
 344
 345         finish_wait(&group->notification_waitq, &wait);
 346         if (start != buf && ret != -EFAULT)
 347                 ret = buf - start;
 348         return ret;
 349 }
 350
 351 static ssize_t fanotify_write(struct file *file, const char __user *buf, size_t count, loff_t *pos)
 352 {
 353 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
 354         struct fanotify_response response = { .fd = -1, .response = -1 };
 355         struct fsnotify_group *group;
 356         int ret;
 357
 358         group = file->private_data;
 359
 360         if (count > sizeof(response))
 361                 count = sizeof(response);
 362
 363         pr_debug("%s: group=%p count=%zu\n", __func__, group, count);
 364
 365         if (copy_from_user(&response, buf, count))
 366                 return -EFAULT;
 367
 368         ret = process_access_response(group, &response);
 369         if (ret < 0)
 370                 count = ret;
 371
 372         return count;
 373 #else
 374         return -EINVAL;
 375 #endif
 376 }
 377
 378 static int fanotify_release(struct inode *ignored, struct file *file)
 379 {
 380         struct fsnotify_group *group = file->private_data;
 381
 382 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
 383         struct fanotify_response_event *re, *lre;
 384
 385         mutex_lock(&group->fanotify_data.access_mutex);
 386
 387         atomic_inc(&group->fanotify_data.bypass_perm);
 388
 389         list_for_each_entry_safe(re, lre, &group->fanotify_data.access_list, list) {
 390                 pr_debug("%s: found group=%p re=%p event=%p\n", __func__, group,
 391                          re, re->event);
 392
 393                 list_del_init(&re->list);
 394                 re->event->response = FAN_ALLOW;
 395
 396                 kmem_cache_free(fanotify_response_event_cache, re);
 397         }
 398         mutex_unlock(&group->fanotify_data.access_mutex);
 399
 400         wake_up(&group->fanotify_data.access_waitq);
 401 #endif
 402
 403         /* matches the fanotify_init->fsnotify_alloc_group */
 404         fsnotify_destroy_group(group);
 405
 406         return 0;
 407 }
 408
 409 static long fanotify_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 410 {
 411         struct fsnotify_group *group;
 412         struct fsnotify_event_holder *holder;
 413         void __user *p;
 414         int ret = -ENOTTY;
 415         size_t send_len = 0;
 416
 417         group = file->private_data;
 418
 419         p = (void __user *) arg;
 420
 421         switch (cmd) {
 422         case FIONREAD:
 423                 mutex_lock(&group->notification_mutex);
 424                 list_for_each_entry(holder, &group->notification_list, event_list)
 425                         send_len += FAN_EVENT_METADATA_LEN;
 426                 mutex_unlock(&group->notification_mutex);
 427                 ret = put_user(send_len, (int __user *) p);
 428                 break;
 429         }
 430
 431         return ret;
 432 }
 433
 434 static const struct file_operations fanotify_fops = {
 435         .show_fdinfo    = fanotify_show_fdinfo,
 436         .poll           = fanotify_poll,
 437         .read           = fanotify_read,
 438         .write          = fanotify_write,
 439         .fasync         = NULL,
 440         .release        = fanotify_release,
 441         .unlocked_ioctl = fanotify_ioctl,
 442         .compat_ioctl   = fanotify_ioctl,
 443         .llseek         = noop_llseek,
 444 };
 445
 446 static void fanotify_free_mark(struct fsnotify_mark *fsn_mark)
 447 {
 448         kmem_cache_free(fanotify_mark_cache, fsn_mark);
 449 }
 450
 451 static int fanotify_find_path(int dfd, const char __user *filename,
 452                               struct path *path, unsigned int flags)
 453 {
 454         int ret;
 455
 456         pr_debug("%s: dfd=%d filename=%p flags=%x\n", __func__,
 457                  dfd, filename, flags);
 458
 459         if (filename == NULL) {
 460                 struct fd f = fdget(dfd);
 461
 462                 ret = -EBADF;
 463                 if (!f.file)
 464                         goto out;
 465
 466                 ret = -ENOTDIR;
 467                 if ((flags & FAN_MARK_ONLYDIR) &&
 468                     !(S_ISDIR(file_inode(f.file)->i_mode))) {
 469                         fdput(f);
 470                         goto out;
 471                 }
 472
 473                 *path = f.file->f_path;
 474                 path_get(path);
 475                 fdput(f);
 476         } else {
 477                 unsigned int lookup_flags = 0;
 478
 479                 if (!(flags & FAN_MARK_DONT_FOLLOW))
 480                         lookup_flags |= LOOKUP_FOLLOW;
 481                 if (flags & FAN_MARK_ONLYDIR)
 482                         lookup_flags |= LOOKUP_DIRECTORY;
 483
 484                 ret = user_path_at(dfd, filename, lookup_flags, path);
 485                 if (ret)
 486                         goto out;
 487         }
 488
 489         /* you can only watch an inode if you have read permissions on it */
 490         ret = inode_permission(path->dentry->d_inode, MAY_READ);
 491         if (ret)
 492                 path_put(path);
 493 out:
 494         return ret;
 495 }
 496
 497 static __u32 fanotify_mark_remove_from_mask(struct fsnotify_mark *fsn_mark,
 498                                             __u32 mask,
 499                                             unsigned int flags,
 500                                             int *destroy)
 501 {
 502         __u32 oldmask;
 503
 504         spin_lock(&fsn_mark->lock);
 505         if (!(flags & FAN_MARK_IGNORED_MASK)) {
 506                 oldmask = fsn_mark->mask;
 507                 fsnotify_set_mark_mask_locked(fsn_mark, (oldmask & ~mask));
 508         } else {
 509                 oldmask = fsn_mark->ignored_mask;
 510                 fsnotify_set_mark_ignored_mask_locked(fsn_mark, (oldmask & ~mask));
 511         }
 512         spin_unlock(&fsn_mark->lock);
 513
 514         *destroy = !(oldmask & ~mask);
 515
 516         return mask & oldmask;
 517 }
 518
 519 static int fanotify_remove_vfsmount_mark(struct fsnotify_group *group,
 520                                          struct vfsmount *mnt, __u32 mask,
 521                                          unsigned int flags)
 522 {
 523         struct fsnotify_mark *fsn_mark = NULL;
 524         __u32 removed;
 525         int destroy_mark;
 526
 527         mutex_lock(&group->mark_mutex);
 528         fsn_mark = fsnotify_find_vfsmount_mark(group, mnt);
 529         if (!fsn_mark) {
 530                 mutex_unlock(&group->mark_mutex);
 531                 return -ENOENT;
 532         }
 533
 534         removed = fanotify_mark_remove_from_mask(fsn_mark, mask, flags,
 535                                                  &destroy_mark);
 536         if (destroy_mark)
 537                 fsnotify_destroy_mark_locked(fsn_mark, group);
 538         mutex_unlock(&group->mark_mutex);
 539
 540         fsnotify_put_mark(fsn_mark);
 541         if (removed & real_mount(mnt)->mnt_fsnotify_mask)
 542                 fsnotify_recalc_vfsmount_mask(mnt);
 543
 544         return 0;
 545 }
 546
 547 static int fanotify_remove_inode_mark(struct fsnotify_group *group,
 548                                       struct inode *inode, __u32 mask,
 549                                       unsigned int flags)
 550 {
 551         struct fsnotify_mark *fsn_mark = NULL;
 552         __u32 removed;
 553         int destroy_mark;
 554
 555         mutex_lock(&group->mark_mutex);
 556         fsn_mark = fsnotify_find_inode_mark(group, inode);
 557         if (!fsn_mark) {
 558                 mutex_unlock(&group->mark_mutex);
 559                 return -ENOENT;
 560         }
 561
 562         removed = fanotify_mark_remove_from_mask(fsn_mark, mask, flags,
 563                                                  &destroy_mark);
 564         if (destroy_mark)
 565                 fsnotify_destroy_mark_locked(fsn_mark, group);
 566         mutex_unlock(&group->mark_mutex);
 567
 568         /* matches the fsnotify_find_inode_mark() */
 569         fsnotify_put_mark(fsn_mark);
 570         if (removed & inode->i_fsnotify_mask)
 571                 fsnotify_recalc_inode_mask(inode);
 572
 573         return 0;
 574 }
 575
 576 static __u32 fanotify_mark_add_to_mask(struct fsnotify_mark *fsn_mark,
 577                                        __u32 mask,
 578                                        unsigned int flags)
 579 {
 580         __u32 oldmask = -1;
 581
 582         spin_lock(&fsn_mark->lock);
 583         if (!(flags & FAN_MARK_IGNORED_MASK)) {
 584                 oldmask = fsn_mark->mask;
 585                 fsnotify_set_mark_mask_locked(fsn_mark, (oldmask | mask));
 586         } else {
 587                 __u32 tmask = fsn_mark->ignored_mask | mask;
 588                 fsnotify_set_mark_ignored_mask_locked(fsn_mark, tmask);
 589                 if (flags & FAN_MARK_IGNORED_SURV_MODIFY)
 590                         fsn_mark->flags |= FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY;
 591         }
 592
 593         if (!(flags & FAN_MARK_ONDIR)) {
 594                 __u32 tmask = fsn_mark->ignored_mask | FAN_ONDIR;
 595                 fsnotify_set_mark_ignored_mask_locked(fsn_mark, tmask);
 596         }
 597
 598         spin_unlock(&fsn_mark->lock);
 599
 600         return mask & ~oldmask;
 601 }
 602
 603 static struct fsnotify_mark *fanotify_add_new_mark(struct fsnotify_group *group,
 604                                                    struct inode *inode,
 605                                                    struct vfsmount *mnt)
 606 {
 607         struct fsnotify_mark *mark;
 608         int ret;
 609
 610         if (atomic_read(&group->num_marks) > group->fanotify_data.max_marks)
 611                 return ERR_PTR(-ENOSPC);
 612
 613         mark = kmem_cache_alloc(fanotify_mark_cache, GFP_KERNEL);
 614         if (!mark)
 615                 return ERR_PTR(-ENOMEM);
 616
 617         fsnotify_init_mark(mark, fanotify_free_mark);
 618         ret = fsnotify_add_mark_locked(mark, group, inode, mnt, 0);
 619         if (ret) {
 620                 fsnotify_put_mark(mark);
 621                 return ERR_PTR(ret);
 622         }
 623
 624         return mark;
 625 }
 626
 627
 628 static int fanotify_add_vfsmount_mark(struct fsnotify_group *group,
 629                                       struct vfsmount *mnt, __u32 mask,
 630                                       unsigned int flags)
 631 {
 632         struct fsnotify_mark *fsn_mark;
 633         __u32 added;
 634
 635         mutex_lock(&group->mark_mutex);
 636         fsn_mark = fsnotify_find_vfsmount_mark(group, mnt);
 637         if (!fsn_mark) {
 638                 fsn_mark = fanotify_add_new_mark(group, NULL, mnt);
 639                 if (IS_ERR(fsn_mark)) {
 640                         mutex_unlock(&group->mark_mutex);
 641                         return PTR_ERR(fsn_mark);
 642                 }
 643         }
 644         added = fanotify_mark_add_to_mask(fsn_mark, mask, flags);
 645         mutex_unlock(&group->mark_mutex);
 646
 647         if (added & ~real_mount(mnt)->mnt_fsnotify_mask)
 648                 fsnotify_recalc_vfsmount_mask(mnt);
 649
 650         fsnotify_put_mark(fsn_mark);
 651         return 0;
 652 }
 653
 654 static int fanotify_add_inode_mark(struct fsnotify_group *group,
 655                                    struct inode *inode, __u32 mask,
 656                                    unsigned int flags)
 657 {
 658         struct fsnotify_mark *fsn_mark;
 659         __u32 added;
 660
 661         pr_debug("%s: group=%p inode=%p\n", __func__, group, inode);
 662
 663         /*
 664          * If some other task has this inode open for write we should not add
 665          * an ignored mark, unless that ignored mark is supposed to survive
 666          * modification changes anyway.
 667          */
 668         if ((flags & FAN_MARK_IGNORED_MASK) &&
 669             !(flags & FAN_MARK_IGNORED_SURV_MODIFY) &&
 670             (atomic_read(&inode->i_writecount) > 0))
 671                 return 0;
 672
 673         mutex_lock(&group->mark_mutex);
 674         fsn_mark = fsnotify_find_inode_mark(group, inode);
 675         if (!fsn_mark) {
 676                 fsn_mark = fanotify_add_new_mark(group, inode, NULL);
 677                 if (IS_ERR(fsn_mark)) {
 678                         mutex_unlock(&group->mark_mutex);
 679                         return PTR_ERR(fsn_mark);
 680                 }
 681         }
 682         added = fanotify_mark_add_to_mask(fsn_mark, mask, flags);
 683         mutex_unlock(&group->mark_mutex);
 684
 685         if (added & ~inode->i_fsnotify_mask)
 686                 fsnotify_recalc_inode_mask(inode);
 687
 688         fsnotify_put_mark(fsn_mark);
 689         return 0;
 690 }
 691
 692 /* fanotify syscalls */
 693 SYSCALL_DEFINE2(fanotify_init, unsigned int, flags, unsigned int, event_f_flags)
 694 {
 695         struct fsnotify_group *group;
 696         int f_flags, fd;
 697         struct user_struct *user;
 698
 699         pr_debug("%s: flags=%d event_f_flags=%d\n",
 700                 __func__, flags, event_f_flags);
 701
 702         if (!capable(CAP_SYS_ADMIN))
 703                 return -EPERM;
 704
 705         if (flags & ~FAN_ALL_INIT_FLAGS)
 706                 return -EINVAL;
 707
 708         user = get_current_user();
 709         if (atomic_read(&user->fanotify_listeners) > FANOTIFY_DEFAULT_MAX_LISTENERS) {
 710                 free_uid(user);
 711                 return -EMFILE;
 712         }
 713
 714         f_flags = O_RDWR | FMODE_NONOTIFY;
 715         if (flags & FAN_CLOEXEC)
 716                 f_flags |= O_CLOEXEC;
 717         if (flags & FAN_NONBLOCK)
 718                 f_flags |= O_NONBLOCK;
 719
 720         /* fsnotify_alloc_group takes a ref.  Dropped in fanotify_release */
 721         group = fsnotify_alloc_group(&fanotify_fsnotify_ops);
 722         if (IS_ERR(group)) {
 723                 free_uid(user);
 724                 return PTR_ERR(group);
 725         }
 726
 727         group->fanotify_data.user = user;
 728         atomic_inc(&user->fanotify_listeners);
 729
 730         group->fanotify_data.f_flags = event_f_flags;
 731 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
 732         mutex_init(&group->fanotify_data.access_mutex);
 733         init_waitqueue_head(&group->fanotify_data.access_waitq);
 734         INIT_LIST_HEAD(&group->fanotify_data.access_list);
 735         atomic_set(&group->fanotify_data.bypass_perm, 0);
 736 #endif
 737         switch (flags & FAN_ALL_CLASS_BITS) {
 738         case FAN_CLASS_NOTIF:
 739                 group->priority = FS_PRIO_0;
 740                 break;
 741         case FAN_CLASS_CONTENT:
 742                 group->priority = FS_PRIO_1;
 743                 break;
 744         case FAN_CLASS_PRE_CONTENT:
 745                 group->priority = FS_PRIO_2;
 746                 break;
 747         default:
 748                 fd = -EINVAL;
 749                 goto out_destroy_group;
 750         }
 751
 752         if (flags & FAN_UNLIMITED_QUEUE) {
 753                 fd = -EPERM;
 754                 if (!capable(CAP_SYS_ADMIN))
 755                         goto out_destroy_group;
 756                 group->max_events = UINT_MAX;
 757         } else {
 758                 group->max_events = FANOTIFY_DEFAULT_MAX_EVENTS;
 759         }
 760
 761         if (flags & FAN_UNLIMITED_MARKS) {
 762                 fd = -EPERM;
 763                 if (!capable(CAP_SYS_ADMIN))
 764                         goto out_destroy_group;
 765                 group->fanotify_data.max_marks = UINT_MAX;
 766         } else {
 767                 group->fanotify_data.max_marks = FANOTIFY_DEFAULT_MAX_MARKS;
 768         }
 769
 770         fd = anon_inode_getfd("[fanotify]", &fanotify_fops, group, f_flags);
 771         if (fd < 0)
 772                 goto out_destroy_group;
 773
 774         return fd;
 775
 776 out_destroy_group:
 777         fsnotify_destroy_group(group);
 778         return fd;
 779 }
 780
 781 SYSCALL_DEFINE5(fanotify_mark, int, fanotify_fd, unsigned int, flags,
 782                               __u64, mask, int, dfd,
 783                               const char  __user *, pathname)
 784 {
 785         struct inode *inode = NULL;
 786         struct vfsmount *mnt = NULL;
 787         struct fsnotify_group *group;
 788         struct fd f;
 789         struct path path;
 790         int ret;
 791
 792         pr_debug("%s: fanotify_fd=%d flags=%x dfd=%d pathname=%p mask=%llx\n",
 793                  __func__, fanotify_fd, flags, dfd, pathname, mask);
 794
 795         /* we only use the lower 32 bits as of right now. */
 796         if (mask & ((__u64)0xffffffff << 32))
 797                 return -EINVAL;
 798
 799         if (flags & ~FAN_ALL_MARK_FLAGS)
 800                 return -EINVAL;
 801         switch (flags & (FAN_MARK_ADD | FAN_MARK_REMOVE | FAN_MARK_FLUSH)) {
 802         case FAN_MARK_ADD:              /* fallthrough */
 803         case FAN_MARK_REMOVE:
 804                 if (!mask)
 805                         return -EINVAL;
 806         case FAN_MARK_FLUSH:
 807                 break;
 808         default:
 809                 return -EINVAL;
 810         }
 811
 812         if (mask & FAN_ONDIR) {
 813                 flags |= FAN_MARK_ONDIR;
 814                 mask &= ~FAN_ONDIR;
 815         }
 816
 817 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
 818         if (mask & ~(FAN_ALL_EVENTS | FAN_ALL_PERM_EVENTS | FAN_EVENT_ON_CHILD))
 819 #else
 820         if (mask & ~(FAN_ALL_EVENTS | FAN_EVENT_ON_CHILD))
 821 #endif
 822                 return -EINVAL;
 823
 824         f = fdget(fanotify_fd);
 825         if (unlikely(!f.file))
 826                 return -EBADF;
 827
 828         /* verify that this is indeed an fanotify instance */
 829         ret = -EINVAL;
 830         if (unlikely(f.file->f_op != &fanotify_fops))
 831                 goto fput_and_out;
 832         group = f.file->private_data;
 833
 834         /*
 835          * group->priority == FS_PRIO_0 == FAN_CLASS_NOTIF.  These are not
 836          * allowed to set permissions events.
 837          */
 838         ret = -EINVAL;
 839         if (mask & FAN_ALL_PERM_EVENTS &&
 840             group->priority == FS_PRIO_0)
 841                 goto fput_and_out;
 842
 843         ret = fanotify_find_path(dfd, pathname, &path, flags);
 844         if (ret)
 845                 goto fput_and_out;
 846
 847         /* inode held in place by reference to path; group by fget on fd */
 848         if (!(flags & FAN_MARK_MOUNT))
 849                 inode = path.dentry->d_inode;
 850         else
 851                 mnt = path.mnt;
 852
 853         /* create/update an inode mark */
 854         switch (flags & (FAN_MARK_ADD | FAN_MARK_REMOVE | FAN_MARK_FLUSH)) {
 855         case FAN_MARK_ADD:
 856                 if (flags & FAN_MARK_MOUNT)
 857                         ret = fanotify_add_vfsmount_mark(group, mnt, mask, flags);
 858                 else
 859                         ret = fanotify_add_inode_mark(group, inode, mask, flags);
 860                 break;
 861         case FAN_MARK_REMOVE:
 862                 if (flags & FAN_MARK_MOUNT)
 863                         ret = fanotify_remove_vfsmount_mark(group, mnt, mask, flags);
 864                 else
 865                         ret = fanotify_remove_inode_mark(group, inode, mask, flags);
 866                 break;
 867         case FAN_MARK_FLUSH:
 868                 if (flags & FAN_MARK_MOUNT)
 869                         fsnotify_clear_vfsmount_marks_by_group(group);
 870                 else
 871                         fsnotify_clear_inode_marks_by_group(group);
 872                 break;
 873         default:
 874                 ret = -EINVAL;
 875         }
 876
 877         path_put(&path);
 878 fput_and_out:
 879         fdput(f);
 880         return ret;
 881 }
 882
 883 #ifdef CONFIG_COMPAT
 884 COMPAT_SYSCALL_DEFINE6(fanotify_mark,
 885                                 int, fanotify_fd, unsigned int, flags,
 886                                 __u32, mask0, __u32, mask1, int, dfd,
 887                                 const char  __user *, pathname)
 888 {
 889         return sys_fanotify_mark(fanotify_fd, flags,
 890 #ifdef __BIG_ENDIAN
 891                                 ((__u64)mask0 << 32) | mask1,
 892 #else
 893                                 ((__u64)mask1 << 32) | mask0,
 894 #endif
 895                                  dfd, pathname);
 896 }
 897 #endif
 898
 899 /*
 900  * fanotify_user_setup - Our initialization function.  Note that we cannot return
 901  * error because we have compiled-in VFS hooks.  So an (unlikely) failure here
 902  * must result in panic().
 903  */
 904 static int __init fanotify_user_setup(void)
 905 {
 906         fanotify_mark_cache = KMEM_CACHE(fsnotify_mark, SLAB_PANIC);
 907         fanotify_response_event_cache = KMEM_CACHE(fanotify_response_event,
 908                                                    SLAB_PANIC);
 909
 910         return 0;
 911 }
 912 device_initcall(fanotify_user_setup);