dm ioctl: fix hang in early create error condition

commit 0f41fcf7 upstream.

The dm_early_create() function (which deals with "dm-mod.create=" kernel
command line option) calls dm_hash_insert() who gets an extra reference
to the md object.

In case of failure, this reference wasn't being released, causing
dm_destroy() to hang, thus hanging the whole boot process.

Fix this by calling __hash_remove() in the error path.

Fixes: 6bbc923d ("dm: add support to directly boot to a mapped device")
Cc: stable@vger.kernel.org
Signed-off-by: Helen Koike <helen.koike@collabora.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/md/dm-ioctl.c

@@ -2069,7 +2069,7 @@ int __init dm_early_create(struct dm_ioctl *dmi,
 	/* alloc table */
 	r = dm_table_create(&t, get_mode(dmi), dmi->target_count, md);
 	if (r)
-		goto err_destroy_dm;
+		goto err_hash_remove;
 
 	/* add targets */
 	for (i = 0; i < dmi->target_count; i++) {
@@ -2116,6 +2116,10 @@ int __init dm_early_create(struct dm_ioctl *dmi,
 
 err_destroy_table:
 	dm_table_destroy(t);
+err_hash_remove:
+	(void) __hash_remove(__get_name_cell(dmi->name));
+	/* release reference from __get_name_cell */
+	dm_put(md);
 err_destroy_dm:
 	dm_put(md);
 	dm_destroy(md);