fsnotify: Allocate overflow events with proper type

Commit 7053aee26a35 "fsnotify: do not share events between notification
groups" used overflow event statically allocated in a group with the
size of the generic notification event. This causes problems because
some code looks at type specific parts of event structure and gets
confused by a random data it sees there and causes crashes.

Fix the problem by allocating overflow event with type corresponding to
the group type so code cannot get confused.

Signed-off-by: Jan Kara <jack@suse.cz>

1 files changed, 13 insertions, 0 deletions

diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c
index b6175fa11bf8..287a22c04149 100644
--- a/fs/notify/fanotify/fanotify_user.c
+++ b/fs/notify/fanotify/fanotify_user.c
@@ -698,6 +698,7 @@ SYSCALL_DEFINE2(fanotify_init, unsigned int, flags, unsigned int, event_f_flags)
         struct fsnotify_group *group;
         int f_flags, fd;
         struct user_struct *user;
+        struct fanotify_event_info *oevent;
 
         pr_debug("%s: flags=%d event_f_flags=%d\n",
                 __func__, flags, event_f_flags);
@@ -730,8 +731,20 @@ SYSCALL_DEFINE2(fanotify_init, unsigned int, flags, unsigned int, event_f_flags)
         group->fanotify_data.user = user;
         atomic_inc(&user->fanotify_listeners);
 
+        oevent = kmem_cache_alloc(fanotify_event_cachep, GFP_KERNEL);
+        if (unlikely(!oevent)) {
+                fd = -ENOMEM;
+                goto out_destroy_group;
+        }
+        group->overflow_event = &oevent->fse;
+        fsnotify_init_event(group->overflow_event, NULL, FS_Q_OVERFLOW);
+        oevent->tgid = get_pid(task_tgid(current));
+        oevent->path.mnt = NULL;
+        oevent->path.dentry = NULL;
+
         group->fanotify_data.f_flags = event_f_flags;
 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
+        oevent->response = 0;
         mutex_init(&group->fanotify_data.access_mutex);
         init_waitqueue_head(&group->fanotify_data.access_waitq);
         INIT_LIST_HEAD(&group->fanotify_data.access_list);