diff options
authorEric Paris <>2010-05-11 17:17:40 -0400
committerGreg Kroah-Hartman <>2010-05-26 14:29:17 -0700
commitc606e701ef469582a991aabd3a6f7816a9a9d351 (patch)
parentbbd7e6ac76997aadf0b827aaca61ba767eb5dd78 (diff)
inotify: race use after free/double free in inotify inode marks
commit e08733446e72b983fed850fc5d8bd21b386feb29 upstream. There is a race in the inotify add/rm watch code. A task can find and remove a mark which doesn't have all of it's references. This can result in a use after free/double free situation. Task A Task B ------------ ----------- inotify_new_watch() allocate a mark (refcnt == 1) add it to the idr inotify_rm_watch() inotify_remove_from_idr() fsnotify_put_mark() refcnt hits 0, free take reference because we are on idr [at this point it is a use after free] [time goes on] refcnt may hit 0 again, double free The fix is to take the reference BEFORE the object can be found in the idr. Signed-off-by: Eric Paris <> Signed-off-by: Greg Kroah-Hartman <>
1 files changed, 6 insertions, 3 deletions
diff --git a/fs/notify/inotify/inotify_user.c b/fs/notify/inotify/inotify_user.c
index ca44337b06ce..22ef16a478a0 100644
--- a/fs/notify/inotify/inotify_user.c
+++ b/fs/notify/inotify/inotify_user.c
@@ -556,21 +556,24 @@ retry:
if (unlikely(!idr_pre_get(&group->inotify_data.idr, GFP_KERNEL)))
goto out_err;
+ /* we are putting the mark on the idr, take a reference */
+ fsnotify_get_mark(&tmp_ientry->fsn_entry);
ret = idr_get_new_above(&group->inotify_data.idr, &tmp_ientry->fsn_entry,
if (ret) {
+ /* we didn't get on the idr, drop the idr reference */
+ fsnotify_put_mark(&tmp_ientry->fsn_entry);
/* idr was out of memory allocate and try again */
if (ret == -EAGAIN)
goto retry;
goto out_err;
- /* we put the mark on the idr, take a reference */
- fsnotify_get_mark(&tmp_ientry->fsn_entry);
/* we are on the idr, now get on the inode */
ret = fsnotify_add_mark(&tmp_ientry->fsn_entry, group, inode);
if (ret) {