Re: [Qemu-devel] [PATCH v2] hostmem: fix crash when querying empty host-nodes property via QMP

[Stefano Garzarella]

On Thu, Feb 14, 2019 at 05:57:33AM -0500, Igor Mammedov wrote:
> QEMU will crashes with
>  qapi/qobject-output-visitor.c:210: qobject_output_complete: Assertion 
> `qov->root && ((&qov->stack)->slh_first == ((void *)0))' failed
> when trying to get value of not set hostmem's "host-nodes"
> property, HostMemoryBackend::host_nodes bitmap doesn't have
> any bits set in it, which leads to find_first_bit() returning
> MAX_NODES and consequently to an early return from
> host_memory_backend_get_host_nodes() without calling visitor.
> 
> Fix it by calling visitor even if "host-nodes" property wasn't
> set before exiting from property getter to return valid empty
> list.
> 
> Signed-off-by: Igor Mammedov <address@hidden>
> ---
> v2:
>   * fixup commit message to put emphasis on property instead
>     local variable host_nodes and make explanation more hopefully
>     more clear. (Markus Armbruster <address@hidden>)
> ---
>  backends/hostmem.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)

Reviewed-by: Stefano Garzarella <address@hidden>