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From: Peter Maydell <peter.maydell@linaro.org>
Date: Thu, 7 Apr 2016 14:05:01 +0100
Message-ID: <CAFEAcA_QqK4yZpx=us5nPnCvghSDK8pMG50ZJXdESHhhzLYBjw@mail.gmail.com>
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Subject: Re: [Qemu-devel] [PATCH v2] net: stellaris_enet: check packet
 length against receive buffer
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To: P J P <ppandit@redhat.com>
Cc: Oleksandr Bazhaniuk <oleksandr.bazhaniuk@intel.com>, Jason Wang <jasowang@redhat.com>, Qemu Developers <qemu-devel@nongnu.org>, Prasad J Pandit <pjp@fedoraproject.org>

On 7 April 2016 at 13:35, P J P <ppandit@redhat.com> wrote:
> From: Prasad J Pandit <pjp@fedoraproject.org>
>
> When receiving packets over Stellaris ethernet controller, it
> uses receive buffer of size 2048 bytes. In case the controller
> accepts large(MTU) packets, it could lead to memory corruption.
> Add check to avoid it.
>
> Reported by: Oleksandr Bazhaniuk <oleksandr.bazhaniuk@intel.com>
>
> Signed-off-by: Prasad J Pandit <pjp@fedoraproject.org>
> ---
>  hw/net/stellaris_enet.c | 10 +++++++++-
>  1 file changed, 9 insertions(+), 1 deletion(-)
>
> Update per review:
>   -> https://lists.gnu.org/archive/html/qemu-devel/2016-04/msg01142.html
>
> diff --git a/hw/net/stellaris_enet.c b/hw/net/stellaris_enet.c
> index 21a4773..eddbe60 100644
> --- a/hw/net/stellaris_enet.c
> +++ b/hw/net/stellaris_enet.c
> @@ -235,8 +235,16 @@ static ssize_t stellaris_enet_receive(NetClientState *nc, const uint8_t *buf, si
>      n = s->next_packet + s->np;
>      if (n >= 31)
>          n -= 31;
> +    if (size >= sizeof(s->rx[n].data) - 6) {
> +        /* If the packet won't fit into the
> +         * emulated 2K RAM, this is reported
> +         * as a FIFO overrun error.
> +         */
> +        s->ris |= SE_INT_FOV;
> +        stellaris_enet_update(s);
> +        return -1;
> +    }

I think you could reasonably put a blank line before and after
the if() {} you've added here.

>      s->np++;
> -

Stray whitespace change.

>      s->rx[n].len = size + 6;
>      p = s->rx[n].data;
>      *(p++) = (size + 6);
> --
> 2.5.5
>

Otherwise
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>

thanks
-- PMM