media: v4l2-async: avoid deleting unlinked ASC entry on link error

v4l2_async_match_notify() creates ancillary media links before adding
asc->asc_subdev_entry to sd->asc_list.

If ancillary link creation fails, the function jumps to
err_call_unbind while asc_subdev_entry has not been linked yet. Async
connections are zero-allocated, so the list entry still has NULL next
and prev pointers on this path. Calling list_del() on it can therefore
dereference NULL instead of returning the original link creation error.

Do not delete asc_subdev_entry from err_call_unbind. There is no list
insertion to undo on this path; the bound callback and sub-device
registration are the operations that need to be rolled back.

Fixes: 28a1295795 ("media: v4l: async: Allow multiple connections between entities")
Cc: stable@vger.kernel.org
Signed-off-by: Xu Rao <raoxu@uniontech.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>

drivers/media/v4l2-core/v4l2-async.c

@@ -392,7 +392,6 @@ static int v4l2_async_match_notify(struct v4l2_async_notifier *notifier,
 
 err_call_unbind:
 	v4l2_async_nf_call_unbind(notifier, sd, asc);
-	list_del(&asc->asc_subdev_entry);
 
 err_unregister_subdev:
 	if (registered)