block: Fail if requested driver is not available

If an explicit driver option is present, but doesn't specify a valid
driver, then bdrv_open() should fail instead of probing the format.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Jeff Cody <jcody@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>

1 files changed, 5 insertions, 0 deletions

diff --git a/block.c b/block.c
index 38078f7cd5..382ea71f4b 100644
--- a/block.c
+++ b/block.c
@@ -1137,6 +1137,11 @@ int bdrv_open(BlockDriverState *bs, const char *filename, QDict *options,
     if (drvname) {
         drv = bdrv_find_format(drvname);
         qdict_del(options, "driver");
+        if (!drv) {
+            error_setg(errp, "Invalid driver: '%s'", drvname);
+            ret = -EINVAL;
+            goto unlink_and_fail;
+        }
     }
 
     if (!drv) {