Re: [Qemu-arm] [Qemu-devel] [PATCH] cadence_gem: fix buffer overflow

[Jason Wang <jasowang@redhat.com>]

On 01/14/2016 05:43 PM, Michael S. Tsirkin wrote:
> gem_receive copies a packet received from network into an rxbuf[2048]
> array on stack, with size limited by descriptor length set by guest.  If
> guest is malicious and specifies a descriptor length that is too large,
> and should packet size exceed array size, this results in a buffer
> overflow.
>
> Reported-by: 刘令 <liuling-it@360.cn>
> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> ---
>  hw/net/cadence_gem.c | 8 ++++++++
>  1 file changed, 8 insertions(+)

Apply to my -net with tweak on commit log (changing receive to transmit
as noticed).

Thanks

>
> diff --git a/hw/net/cadence_gem.c b/hw/net/cadence_gem.c
> index 3639fc1..15a0786 100644
> --- a/hw/net/cadence_gem.c
> +++ b/hw/net/cadence_gem.c
> @@ -862,6 +862,14 @@ static void gem_transmit(CadenceGEMState *s)
>              break;
>          }
>  
> +        if (tx_desc_get_length(desc) > sizeof(tx_packet) - (p - tx_packet)) {
> +            DB_PRINT("TX descriptor @ 0x%x too large: size 0x%x space 0x%x\n",
> +                     (unsigned)packet_desc_addr,
> +                     (unsigned)tx_desc_get_length(desc),
> +                     sizeof(tx_packet) - (p - tx_packet));
> +            break;
> +        }
> +
>          /* Gather this fragment of the packet from "dma memory" to our contig.
>           * buffer.
>           */