fs/notify/fanotify/fanotify.c

   1 #include <linux/fanotify.h>
   2 #include <linux/fdtable.h>
   3 #include <linux/fsnotify_backend.h>
   4 #include <linux/init.h>
   5 #include <linux/jiffies.h>
   6 #include <linux/kernel.h> /* UINT_MAX */
   7 #include <linux/mount.h>
   8 #include <linux/sched.h>
   9 #include <linux/types.h>
  10 #include <linux/wait.h>
  11
  12 static bool should_merge(struct fsnotify_event *old, struct fsnotify_event *new)
  13 {
  14         pr_debug("%s: old=%p new=%p\n", __func__, old, new);
  15
  16         if (old->to_tell == new->to_tell &&
  17             old->data_type == new->data_type &&
  18             old->tgid == new->tgid) {
  19                 switch (old->data_type) {
  20                 case (FSNOTIFY_EVENT_PATH):
  21                         if ((old->path.mnt == new->path.mnt) &&
  22                             (old->path.dentry == new->path.dentry))
  23                                 return true;
  24                         break;
  25                 case (FSNOTIFY_EVENT_NONE):
  26                         return true;
  27                 default:
  28                         BUG();
  29                 };
  30         }
  31         return false;
  32 }
  33
  34 /* and the list better be locked by something too! */
  35 static struct fsnotify_event *fanotify_merge(struct list_head *list,
  36                                              struct fsnotify_event *event)
  37 {
  38         struct fsnotify_event_holder *test_holder;
  39         struct fsnotify_event *test_event = NULL;
  40         struct fsnotify_event *new_event;
  41
  42         pr_debug("%s: list=%p event=%p\n", __func__, list, event);
  43
  44
  45         list_for_each_entry_reverse(test_holder, list, event_list) {
  46                 if (should_merge(test_holder->event, event)) {
  47                         test_event = test_holder->event;
  48                         break;
  49                 }
  50         }
  51
  52         if (!test_event)
  53                 return NULL;
  54
  55         fsnotify_get_event(test_event);
  56
  57         /* if they are exactly the same we are done */
  58         if (test_event->mask == event->mask)
  59                 return test_event;
  60
  61         /*
  62          * if the refcnt == 2 this is the only queue
  63          * for this event and so we can update the mask
  64          * in place.
  65          */
  66         if (atomic_read(&test_event->refcnt) == 2) {
  67                 test_event->mask |= event->mask;
  68                 return test_event;
  69         }
  70
  71         new_event = fsnotify_clone_event(test_event);
  72
  73         /* done with test_event */
  74         fsnotify_put_event(test_event);
  75
  76         /* couldn't allocate memory, merge was not possible */
  77         if (unlikely(!new_event))
  78                 return ERR_PTR(-ENOMEM);
  79
  80         /* build new event and replace it on the list */
  81         new_event->mask = (test_event->mask | event->mask);
  82         fsnotify_replace_event(test_holder, new_event);
  83
  84         /* we hold a reference on new_event from clone_event */
  85         return new_event;
  86 }
  87
  88 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
  89 static int fanotify_get_response_from_access(struct fsnotify_group *group,
  90                                              struct fsnotify_event *event)
  91 {
  92         int ret;
  93
  94         pr_debug("%s: group=%p event=%p\n", __func__, group, event);
  95
  96         wait_event(group->fanotify_data.access_waitq, event->response ||
  97                                 atomic_read(&group->fanotify_data.bypass_perm));
  98
  99         if (!event->response) /* bypass_perm set */
 100                 return 0;
 101
 102         /* userspace responded, convert to something usable */
 103         spin_lock(&event->lock);
 104         switch (event->response) {
 105         case FAN_ALLOW:
 106                 ret = 0;
 107                 break;
 108         case FAN_DENY:
 109         default:
 110                 ret = -EPERM;
 111         }
 112         event->response = 0;
 113         spin_unlock(&event->lock);
 114
 115         pr_debug("%s: group=%p event=%p about to return ret=%d\n", __func__,
 116                  group, event, ret);
 117
 118         return ret;
 119 }
 120 #endif
 121
 122 static int fanotify_handle_event(struct fsnotify_group *group,
 123                                  struct fsnotify_mark *inode_mark,
 124                                  struct fsnotify_mark *fanotify_mark,
 125                                  struct fsnotify_event *event)
 126 {
 127         int ret = 0;
 128         struct fsnotify_event *notify_event = NULL;
 129
 130         BUILD_BUG_ON(FAN_ACCESS != FS_ACCESS);
 131         BUILD_BUG_ON(FAN_MODIFY != FS_MODIFY);
 132         BUILD_BUG_ON(FAN_CLOSE_NOWRITE != FS_CLOSE_NOWRITE);
 133         BUILD_BUG_ON(FAN_CLOSE_WRITE != FS_CLOSE_WRITE);
 134         BUILD_BUG_ON(FAN_OPEN != FS_OPEN);
 135         BUILD_BUG_ON(FAN_EVENT_ON_CHILD != FS_EVENT_ON_CHILD);
 136         BUILD_BUG_ON(FAN_Q_OVERFLOW != FS_Q_OVERFLOW);
 137         BUILD_BUG_ON(FAN_OPEN_PERM != FS_OPEN_PERM);
 138         BUILD_BUG_ON(FAN_ACCESS_PERM != FS_ACCESS_PERM);
 139         BUILD_BUG_ON(FAN_ONDIR != FS_ISDIR);
 140
 141         pr_debug("%s: group=%p event=%p\n", __func__, group, event);
 142
 143         notify_event = fsnotify_add_notify_event(group, event, NULL, fanotify_merge);
 144         if (IS_ERR(notify_event))
 145                 return PTR_ERR(notify_event);
 146
 147 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
 148         if (event->mask & FAN_ALL_PERM_EVENTS) {
 149                 /* if we merged we need to wait on the new event */
 150                 if (notify_event)
 151                         event = notify_event;
 152                 ret = fanotify_get_response_from_access(group, event);
 153         }
 154 #endif
 155
 156         if (notify_event)
 157                 fsnotify_put_event(notify_event);
 158
 159         return ret;
 160 }
 161
 162 static bool fanotify_should_send_event(struct fsnotify_group *group,
 163                                        struct inode *to_tell,
 164                                        struct fsnotify_mark *inode_mark,
 165                                        struct fsnotify_mark *vfsmnt_mark,
 166                                        __u32 event_mask, void *data, int data_type)
 167 {
 168         __u32 marks_mask, marks_ignored_mask;
 169         struct path *path = data;
 170
 171         pr_debug("%s: group=%p to_tell=%p inode_mark=%p vfsmnt_mark=%p "
 172                  "mask=%x data=%p data_type=%d\n", __func__, group, to_tell,
 173                  inode_mark, vfsmnt_mark, event_mask, data, data_type);
 174
 175         /* if we don't have enough info to send an event to userspace say no */
 176         if (data_type != FSNOTIFY_EVENT_PATH)
 177                 return false;
 178
 179         /* sorry, fanotify only gives a damn about files and dirs */
 180         if (!S_ISREG(path->dentry->d_inode->i_mode) &&
 181             !S_ISDIR(path->dentry->d_inode->i_mode))
 182                 return false;
 183
 184         if (inode_mark && vfsmnt_mark) {
 185                 marks_mask = (vfsmnt_mark->mask | inode_mark->mask);
 186                 marks_ignored_mask = (vfsmnt_mark->ignored_mask | inode_mark->ignored_mask);
 187         } else if (inode_mark) {
 188                 /*
 189                  * if the event is for a child and this inode doesn't care about
 190                  * events on the child, don't send it!
 191                  */
 192                 if ((event_mask & FS_EVENT_ON_CHILD) &&
 193                     !(inode_mark->mask & FS_EVENT_ON_CHILD))
 194                         return false;
 195                 marks_mask = inode_mark->mask;
 196                 marks_ignored_mask = inode_mark->ignored_mask;
 197         } else if (vfsmnt_mark) {
 198                 marks_mask = vfsmnt_mark->mask;
 199                 marks_ignored_mask = vfsmnt_mark->ignored_mask;
 200         } else {
 201                 BUG();
 202         }
 203
 204         if (S_ISDIR(path->dentry->d_inode->i_mode) &&
 205             (marks_ignored_mask & FS_ISDIR))
 206                 return false;
 207
 208         if (event_mask & marks_mask & ~marks_ignored_mask)
 209                 return true;
 210
 211         return false;
 212 }
 213
 214 static void fanotify_free_group_priv(struct fsnotify_group *group)
 215 {
 216         struct user_struct *user;
 217
 218         user = group->fanotify_data.user;
 219         atomic_dec(&user->fanotify_listeners);
 220         free_uid(user);
 221 }
 222
 223 const struct fsnotify_ops fanotify_fsnotify_ops = {
 224         .handle_event = fanotify_handle_event,
 225         .should_send_event = fanotify_should_send_event,
 226         .free_group_priv = fanotify_free_group_priv,
 227         .free_event_priv = NULL,
 228         .freeing_mark = NULL,
 229 };