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, 12 insertions, 0 deletions

diff --git a/fs/notify/inotify/inotify_user.c b/fs/notify/inotify/inotify_user.c
index 6528b5a54ca0..78a2ca3966c3 100644
--- a/fs/notify/inotify/inotify_user.c
+++ b/fs/notify/inotify/inotify_user.c
@@ -633,11 +633,23 @@ static int inotify_update_watch(struct fsnotify_group *group, struct inode *inod
 static struct fsnotify_group *inotify_new_group(unsigned int max_events)
 {
         struct fsnotify_group *group;
+        struct inotify_event_info *oevent;
 
         group = fsnotify_alloc_group(&inotify_fsnotify_ops);
         if (IS_ERR(group))
                 return group;
 
+        oevent = kmalloc(sizeof(struct inotify_event_info), GFP_KERNEL);
+        if (unlikely(!oevent)) {
+                fsnotify_destroy_group(group);
+                return ERR_PTR(-ENOMEM);
+        }
+        group->overflow_event = &oevent->fse;
+        fsnotify_init_event(group->overflow_event, NULL, FS_Q_OVERFLOW);
+        oevent->wd = -1;
+        oevent->sync_cookie = 0;
+        oevent->name_len = 0;
+
         group->max_events = max_events;
 
         spin_lock_init(&group->inotify_data.idr_lock);