RE: [PATCH] net/virtio: fix Rx checksum calculation

["Wangyunjian(wangyunjian,TongTu)" <wangyunjian@huawei.com>]

> -----Original Message-----
> From: Maxime Coquelin [mailto:maxime.coquelin@redhat.com]
> Sent: Tuesday, December 17, 2024 11:33 PM
> To: dev@dpdk.org
> Cc: Olivier Matz <olivier.matz@6wind.com>; Maxime Gouin
> <maxime.gouin@6wind.com>; Maxime Coquelin
> <maxime.coquelin@redhat.com>
> Subject: [PATCH] net/virtio: fix Rx checksum calculation
> 
> From: Olivier Matz <olivier.matz@6wind.com>
> 
> If hdr->csum_start is larger than packet length, the len argument passed
> to rte_raw_cksum_mbuf() overflows and causes a segmentation fault.
> 
> Ignore checksum computation in this case.
> 
> CVE-2024-11614
> 
> Fixes: ca7036b4af3a ("vhost: fix offload flags in Rx path")
> 
> Signed-off-by: Maxime Gouin <maxime.gouin@6wind.com>
> Signed-off-by: Olivier Matz <olivier.matz@6wind.com>
> Reviewed-by: Maxime Coquelin <maxime.coquelin@redhat.com>
> ---
>  lib/vhost/virtio_net.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/lib/vhost/virtio_net.c b/lib/vhost/virtio_net.c
> index d764d4bc6a..69901ab3b5 100644
> --- a/lib/vhost/virtio_net.c
> +++ b/lib/vhost/virtio_net.c
> @@ -2823,6 +2823,9 @@ vhost_dequeue_offload(struct virtio_net *dev,
> struct virtio_net_hdr *hdr,
>  			 */
>  			uint16_t csum = 0, off;
> 
> +			if (hdr->csum_start >= rte_pktmbuf_pkt_len(m))
> +				return;
> +

The hdr->csum_start does two successive reads from user space to read
a variable length data structure. The result overflow if the data structure
changes between the two reads.

We can prevent double fetch issue by using the temporary variable csum_start.

Thanks,
Yunjian

>  			if (rte_raw_cksum_mbuf(m, hdr->csum_start,
>  					rte_pktmbuf_pkt_len(m) - hdr->csum_start, &csum) <
> 0)
>  				return;
> --
> 2.47.0