block: Check create_opts before image creation

If a driver supports image creation, it needs to set the .create_opts
field. We can use that to make sure .create_opts for both drivers
involved is not NULL in bdrv_img_create(), which is important so that
the create_opts pointer in that function is not NULL after the
qemu_opts_append() calls and when going into qemu_opts_create().

Cc: qemu-stable@nongnu.org
Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
(cherry picked from commit c6149724080af7b3d5d61eac8942655e6d212783)
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>

diff --git a/block.c b/block.c
index a6197da71faa9888a5eb6d17e840ec661c8c102b..07f58fcf1b4e2fc178bc3009989edede2bfa8a91 100644 (file)
--- a/block.c
+++ b/block.c
@@ -5534,6 +5534,18 @@ void bdrv_img_create(const char *filename, const char *fmt,
         return;
     }
 
+    if (!drv->create_opts) {
+        error_setg(errp, "Format driver '%s' does not support image creation",
+                   drv->format_name);
+        return;
+    }
+
+    if (!proto_drv->create_opts) {
+        error_setg(errp, "Protocol driver '%s' does not support image creation",
+                   proto_drv->format_name);
+        return;
+    }
+
     create_opts = qemu_opts_append(create_opts, drv->create_opts);
     create_opts = qemu_opts_append(create_opts, proto_drv->create_opts);