On Mon, Nov 30, 2015 at 03:38:22PM +0800, Jason Wang wrote:
> From: Prasad J Pandit <p...@fedoraproject.org>
>
> In loopback mode, pcnet_receive routine appends CRC code to the
> receive buffer. If the data size given is same as the buffer size,
> the appended CRC code overwrites 4 bytes after s->buffer. Added a
> check to avoid that.
>
> Reported by: Qinghao Tang <luodalon...@gmail.com>
> Cc: qemu-sta...@nongnu.org
> Signed-off-by: Prasad J Pandit <p...@fedoraproject.org>
> Signed-off-by: Jason Wang <jasow...@redhat.com>
Reviewed-by: Michael S. Tsirkin <m...@redhat.com>
> ---
> hw/net/pcnet.c | 8 +++++---
> 1 file changed, 5 insertions(+), 3 deletions(-)
>
> diff --git a/hw/net/pcnet.c b/hw/net/pcnet.c
> index 0eb3cc4..309c40b 100644
> --- a/hw/net/pcnet.c
> +++ b/hw/net/pcnet.c
> @@ -1084,7 +1084,7 @@ ssize_t pcnet_receive(NetClientState *nc, const uint8_t
> *buf, size_t size_)
> uint32_t fcs = ~0;
> uint8_t *p = src;
>
> - while (p != &src[size-4])
> + while (p != &src[size])
> CRC(fcs, *p++);
> crc_err = (*(uint32_t *)p != htonl(fcs));
> }
> @@ -1233,8 +1233,10 @@ static void pcnet_transmit(PCNetState *s)
> bcnt = 4096 - GET_FIELD(tmd.length, TMDL, BCNT);
>
> /* if multi-tmd packet outsizes s->buffer then skip it silently.
> - Note: this is not what real hw does */
> - if (s->xmit_pos + bcnt > sizeof(s->buffer)) {
> + * Note: this is not what real hw does.
> + * Last four bytes of s->buffer are used to store CRC FCS code.
> + */
> + if (s->xmit_pos + bcnt > sizeof(s->buffer) - 4) {
> s->xmit_pos = -1;
> goto txdone;
> }
> --
> 2.5.0
>
