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: [email protected]
Signed-off-by: Max Reitz <[email protected]>
Reviewed-by: Kevin Wolf <[email protected]>
Signed-off-by: Kevin Wolf <[email protected]>
(cherry picked from commit c614972)
Signed-off-by: Michael Roth <[email protected]>

Author: XanClic

block.c

@@ -5528,6 +5528,18 @@ 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);