fanotify: fix double free of pending permission events

[cascardo/linux.git] / fs / notify / fanotify / fanotify_user.c

diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c
index fbf2210..b13992a 100644 (file)
--- a/fs/notify/fanotify/fanotify_user.c
+++ b/fs/notify/fanotify/fanotify_user.c
@@ -359,6 +359,11 @@ static int fanotify_release(struct inode *ignored, struct file *file)
 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
        struct fanotify_perm_event_info *event, *next;
 
+       /*
+        * There may be still new events arriving in the notification queue
+        * but since userspace cannot use fanotify fd anymore, no event can
+        * enter or leave access_list by now.
+        */
        spin_lock(&group->fanotify_data.access_lock);
 
        atomic_inc(&group->fanotify_data.bypass_perm);
@@ -373,6 +378,13 @@ static int fanotify_release(struct inode *ignored, struct file *file)
        }
        spin_unlock(&group->fanotify_data.access_lock);
 
+       /*
+        * Since bypass_perm is set, newly queued events will not wait for
+        * access response. Wake up the already sleeping ones now.
+        * synchronize_srcu() in fsnotify_destroy_group() will wait for all
+        * processes sleeping in fanotify_handle_event() waiting for access
+        * response and thus also for all permission events to be freed.
+        */
        wake_up(&group->fanotify_data.access_waitq);
 #endif