Re: [Qemu-devel] [PATCH v2] pc: fix possible NULL pointer dereference in pc_machine_get_device_memory_region_size()

[Philippe Mathieu-Daudé]

On 6/24/19 11:02 AM, Igor Mammedov wrote:
> QEMU will crash when device-memory-region-size property is read if 
> ms->device_memory
> wasn't initialized yet.
> 
> Crash can be reproduced with:
>  $QEMU -preconfig -qmp unix:qmp_socket,server,nowait &
>  ./scripts/qmp/qom-get -s qmp_socket /machine.device-memory-region-size
> 
> Instead of crashing return 0 if ms->device_memory hasn't been initialized.
> 
> Signed-off-by: Igor Mammedov <address@hidden>

Reviewed-by: Philippe Mathieu-Daudé <address@hidden>

> ---
> 
> v2:
>   * fix missing return value assignment
>       (Eduardo Habkost <address@hidden>)
> ---
>  hw/i386/pc.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/hw/i386/pc.c b/hw/i386/pc.c
> index e96360b47a..552f3401e2 100644
> --- a/hw/i386/pc.c
> +++ b/hw/i386/pc.c
> @@ -2458,7 +2458,11 @@ pc_machine_get_device_memory_region_size(Object *obj, 
> Visitor *v,
>                                           Error **errp)
>  {
>      MachineState *ms = MACHINE(obj);
> -    int64_t value = memory_region_size(&ms->device_memory->mr);
> +    int64_t value = 0;
> +
> +    if (ms->device_memory) {
> +        value = memory_region_size(&ms->device_memory->mr);
> +    }
>  
>      visit_type_int(v, name, &value, errp);
>  }
>