net/virtio: fix Rx checksum calculation

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: ca7036b ("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

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