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_FILE):
  21                         if ((old->file->f_path.mnt == new->file->f_path.mnt) &&
  22                             (old->file->f_path.dentry == new->file->f_path.dentry))
  23                                 return true;
  24                 case (FSNOTIFY_EVENT_NONE):
  25                         return true;
  26                 default:
  27                         BUG();
  28                 };
  29         }
  30         return false;
  31 }
  32
  33 /* and the list better be locked by something too! */
  34 static struct fsnotify_event *fanotify_merge(struct list_head *list,
  35                                              struct fsnotify_event *event)
  36 {
  37         struct fsnotify_event_holder *test_holder;
  38         struct fsnotify_event *test_event = NULL;
  39         struct fsnotify_event *new_event;
  40
  41         pr_debug("%s: list=%p event=%p\n", __func__, list, event);
  42
  43
  44         list_for_each_entry_reverse(test_holder, list, event_list) {
  45                 if (should_merge(test_holder->event, event)) {
  46                         test_event = test_holder->event;
  47                         break;
  48                 }
  49         }
  50
  51         if (!test_event)
  52                 return NULL;
  53
  54         fsnotify_get_event(test_event);
  55
  56         /* if they are exactly the same we are done */
  57         if (test_event->mask == event->mask)
  58                 return test_event;
  59
  60         /*
  61          * if the refcnt == 2 this is the only queue
  62          * for this event and so we can update the mask
  63          * in place.
  64          */
  65         if (atomic_read(&test_event->refcnt) == 2) {
  66                 test_event->mask |= event->mask;
  67                 return test_event;
  68         }
  69
  70         new_event = fsnotify_clone_event(test_event);
  71
  72         /* done with test_event */
  73         fsnotify_put_event(test_event);
  74
  75         /* couldn't allocate memory, merge was not possible */
  76         if (unlikely(!new_event))
  77                 return ERR_PTR(-ENOMEM);
  78
  79         /* build new event and replace it on the list */
  80         new_event->mask = (test_event->mask | event->mask);
  81         fsnotify_replace_event(test_holder, new_event);
  82
  83         /* we hold a reference on new_event from clone_event */
  84         return new_event;
  85 }
  86
  87 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
  88 static int fanotify_get_response_from_access(struct fsnotify_group *group,
  89                                              struct fsnotify_event *event)
  90 {
  91         int ret;
  92
  93         pr_debug("%s: group=%p event=%p\n", __func__, group, event);
  94
  95         wait_event(group->fanotify_data.access_waitq, event->response);
  96
  97         /* userspace responded, convert to something usable */
  98         spin_lock(&event->lock);
  99         switch (event->response) {
 100         case FAN_ALLOW:
 101                 ret = 0;
 102                 break;
 103         case FAN_DENY:
 104         default:
 105                 ret = -EPERM;
 106         }
 107         event->response = 0;
 108         spin_unlock(&event->lock);
 109
 110         pr_debug("%s: group=%p event=%p about to return ret=%d\n", __func__,
 111                  group, event, ret);
 112
 113         return ret;
 114 }
 115 #endif
 116
 117 static int fanotify_handle_event(struct fsnotify_group *group,
 118                                  struct fsnotify_mark *mark,
 119                                  struct fsnotify_event *event)
 120 {
 121         int ret = 0;
 122         struct fsnotify_event *notify_event = NULL;
 123
 124         BUILD_BUG_ON(FAN_ACCESS != FS_ACCESS);
 125         BUILD_BUG_ON(FAN_MODIFY != FS_MODIFY);
 126         BUILD_BUG_ON(FAN_CLOSE_NOWRITE != FS_CLOSE_NOWRITE);
 127         BUILD_BUG_ON(FAN_CLOSE_WRITE != FS_CLOSE_WRITE);
 128         BUILD_BUG_ON(FAN_OPEN != FS_OPEN);
 129         BUILD_BUG_ON(FAN_EVENT_ON_CHILD != FS_EVENT_ON_CHILD);
 130         BUILD_BUG_ON(FAN_Q_OVERFLOW != FS_Q_OVERFLOW);
 131         BUILD_BUG_ON(FAN_OPEN_PERM != FS_OPEN_PERM);
 132         BUILD_BUG_ON(FAN_ACCESS_PERM != FS_ACCESS_PERM);
 133
 134         pr_debug("%s: group=%p event=%p\n", __func__, group, event);
 135
 136         notify_event = fsnotify_add_notify_event(group, event, NULL, fanotify_merge);
 137         if (IS_ERR(notify_event))
 138                 return PTR_ERR(notify_event);
 139
 140 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
 141         if (event->mask & FAN_ALL_PERM_EVENTS) {
 142                 /* if we merged we need to wait on the new event */
 143                 if (notify_event)
 144                         event = notify_event;
 145                 ret = fanotify_get_response_from_access(group, event);
 146         }
 147 #endif
 148
 149         if (notify_event)
 150                 fsnotify_put_event(notify_event);
 151
 152         return ret;
 153 }
 154
 155 static bool should_send_vfsmount_event(struct fsnotify_group *group,
 156                                        struct vfsmount *mnt,
 157                                        struct inode *inode,
 158                                        struct fsnotify_mark *mnt_mark,
 159                                        __u32 mask)
 160 {
 161         struct fsnotify_mark *inode_mark;
 162
 163         pr_debug("%s: group=%p vfsmount=%p mark=%p mask=%x\n",
 164                  __func__, group, mnt, mnt_mark, mask);
 165
 166         mask &= mnt_mark->mask;
 167         mask &= ~mnt_mark->ignored_mask;
 168
 169         if (mask) {
 170                 inode_mark = fsnotify_find_inode_mark(group, inode);
 171                 if (inode_mark) {
 172                         mask &= ~inode_mark->ignored_mask;
 173                         fsnotify_put_mark(inode_mark);
 174                 }
 175         }
 176
 177         return mask;
 178 }
 179
 180 static bool should_send_inode_event(struct fsnotify_group *group,
 181                                     struct inode *inode,
 182                                     struct fsnotify_mark *mark,
 183                                     __u32 mask)
 184 {
 185         pr_debug("%s: group=%p inode=%p mark=%p mask=%x\n",
 186                  __func__, group, inode, mark, mask);
 187
 188         /* if the event is for a child and this inode doesn't care about
 189          * events on the child, don't send it! */
 190         if ((mask & FS_EVENT_ON_CHILD) &&
 191             !(mark->mask & FS_EVENT_ON_CHILD)) {
 192                 mask = 0;
 193         } else {
 194                 /*
 195                  * We care about children, but do we care about this particular
 196                  * type of event?
 197                  */
 198                 mask &= ~FS_EVENT_ON_CHILD;
 199                 mask &= mark->mask;
 200                 mask &= ~mark->ignored_mask;
 201         }
 202
 203         return mask;
 204 }
 205
 206 static bool fanotify_should_send_event(struct fsnotify_group *group, struct inode *to_tell,
 207                                        struct vfsmount *mnt, struct fsnotify_mark *mark,
 208                                        __u32 mask, void *data, int data_type)
 209 {
 210         pr_debug("%s: group=%p to_tell=%p mnt=%p mask=%x data=%p data_type=%d\n",
 211                  __func__, group, to_tell, mnt, mask, data, data_type);
 212
 213         /* sorry, fanotify only gives a damn about files and dirs */
 214         if (!S_ISREG(to_tell->i_mode) &&
 215             !S_ISDIR(to_tell->i_mode))
 216                 return false;
 217
 218         /* if we don't have enough info to send an event to userspace say no */
 219         if (data_type != FSNOTIFY_EVENT_FILE)
 220                 return false;
 221
 222         if (mnt)
 223                 return should_send_vfsmount_event(group, mnt, to_tell, mark, mask);
 224         else
 225                 return should_send_inode_event(group, to_tell, mark, mask);
 226 }
 227
 228 const struct fsnotify_ops fanotify_fsnotify_ops = {
 229         .handle_event = fanotify_handle_event,
 230         .should_send_event = fanotify_should_send_event,
 231         .free_group_priv = NULL,
 232         .free_event_priv = NULL,
 233         .freeing_mark = NULL,
 234 };