An active node makes unrestricted use of its children and would possibly
run into assertion failures when it operates on an inactive child node.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
 block.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/block.c b/block.c
index f60606f242..94368a200e 100644
--- a/block.c
+++ b/block.c
@@ -3183,6 +3183,11 @@ bdrv_attach_child_noperm(BlockDriverState *parent_bs,
                    child_bs->node_name, child_name, parent_bs->node_name);
         return NULL;
     }
+    if (bdrv_is_inactive(child_bs) && !bdrv_is_inactive(parent_bs)) {
+        error_setg(errp, "Inactive '%s' can't be a %s child of active '%s'",
+                   child_bs->node_name, child_name, parent_bs->node_name);
+        return NULL;
+    }
 
     bdrv_get_cumulative_perm(parent_bs, &perm, &shared_perm);
     bdrv_child_perm(parent_bs, child_bs, NULL, child_role, NULL,
-- 
2.48.1

On Thu, Jan 30, 2025 at 06:12:35PM +0100, Kevin Wolf wrote:
> An active node makes unrestricted use of its children and would possibly
> run into assertion failures when it operates on an inactive child node.
> 
> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> ---
>  block.c | 5 +++++
>  1 file changed, 5 insertions(+)

Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>

On Thu, Jan 30, 2025 at 06:12:35PM +0100, Kevin Wolf wrote:
> An active node makes unrestricted use of its children and would possibly
> run into assertion failures when it operates on an inactive child node.
> 
> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> ---
>  block.c | 5 +++++
>  1 file changed, 5 insertions(+)

Reviewed-by: Eric Blake <eblake@redhat.com>

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.
Virtualization:  qemu.org | libguestfs.org