[Qemu-devel] [PATCH v2] net: stellaris_enet: check packet length against receive buffer

[Qemu-devel] [PATCH v2] net: stellaris_enet: check packet length against receive buffer

[P J P]

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

Re: [Qemu-devel] [PATCH v2] net: stellaris_enet: check packet length against receive buffer

[Peter Maydell]

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

Re: [Qemu-devel] [PATCH v2] net: stellaris_enet: check packet length against receive buffer

[P J P]

+-- On Thu, 7 Apr 2016, Peter Maydell wrote --+
| I think you could reasonably put a blank line before and after
| the if() {} you've added here.

Sent a revised patch v3. Thank you.
--
Prasad J Pandit / Red Hat Product Security Team
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