vhost: do not GSO when no header is present

Found with clang static analysis:
lib/librte_vhost/virtio_net.c:723:17: warning:
Access to field 'data_off' results in a dereference of a null pointer
(loaded from variable 'tcp_hdr')
        m->l4_len = (tcp_hdr->data_off & 0xf0) >> 2;
                     ^~~~~~~~~~~~~~~~~

Fixes: d0cf91303d73 ("vhost: add Tx offload capabilities")
Cc: stable@dpdk.org
Signed-off-by: Emmanuel Roullit <emmanuel.roullit@gmail.com>
Acked-by: Yuanhan Liu <yuanhan.liu@linux.intel.com>

diff --git a/lib/librte_vhost/virtio_net.c b/lib/librte_vhost/virtio_net.c
index 143c0fa..337470d 100644 (file)
--- a/lib/librte_vhost/virtio_net.c
+++ b/lib/librte_vhost/virtio_net.c
@@ -679,6 +679,7 @@ parse_ethernet(struct rte_mbuf *m, uint16_t *l4_proto, void **l4_hdr)
        default:
                m->l3_len = 0;
                *l4_proto = 0;
+               *l4_hdr = NULL;
                break;
        }
 }
@@ -715,7 +716,7 @@ vhost_dequeue_offload(struct virtio_net_hdr *hdr, struct rte_mbuf *m)
                }
        }
 
-       if (hdr->gso_type != VIRTIO_NET_HDR_GSO_NONE) {
+       if (l4_hdr && hdr->gso_type != VIRTIO_NET_HDR_GSO_NONE) {
                switch (hdr->gso_type & ~VIRTIO_NET_HDR_GSO_ECN) {
                case VIRTIO_NET_HDR_GSO_TCPV4:
                case VIRTIO_NET_HDR_GSO_TCPV6: