Re: [PATCH] acpi: validate hotplug selector on access

[Ani Sinha]

On Tue, 21 Dec 2021, Michael S. Tsirkin wrote:

> When bus is looked up on a pci write, we didn't
> validate that the lookup succeeded.
> Fuzzers thus can trigger QEMU crash by dereferencing the NULL
> bus pointer.

Good fix. Nice catch.

>
> Fixes: b32bd763a1 ("pci: introduce acpi-index property for PCI device")
> Cc: "Igor Mammedov" <imammedo@redhat.com>
> Fixes: https://gitlab.com/qemu-project/qemu/-/issues/770
> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

Reviewed-by: Ani Sinha <ani@anisinha.ca>

> ---
>  hw/acpi/pcihp.c | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/hw/acpi/pcihp.c b/hw/acpi/pcihp.c
> index 30405b5113..a5e182dd3a 100644
> --- a/hw/acpi/pcihp.c
> +++ b/hw/acpi/pcihp.c
> @@ -491,6 +491,9 @@ static void pci_write(void *opaque, hwaddr addr, uint64_t 
> data,
>          }
>
>          bus = acpi_pcihp_find_hotplug_bus(s, s->hotplug_select);
> +        if (!bus) {
> +            break;
> +        }
>          QTAILQ_FOREACH_SAFE(kid, &bus->qbus.children, sibling, next) {
>              Object *o = OBJECT(kid->child);
>              PCIDevice *dev = PCI_DEVICE(o);
> --
> MST
>
>