vhost: fix initialization of temporary header

[ upstream commit 5b784a2 ]

This patch fixs coverity issue by adding initialization step before
using temporary virtio header.

Coverity issue: 366181
Fixes: fb3815c ("vhost: handle virtually non-contiguous buffers in Rx-mrg")

Signed-off-by: Marvin Liu <yong.liu@intel.com>
Reviewed-by: Maxime Coquelin <maxime.coquelin@redhat.com>

lib/librte_vhost/virtio_net.c

@@ -835,9 +835,10 @@ copy_mbuf_to_desc(struct virtio_net *dev, struct vhost_virtqueue *vq,
 
 	hdr_mbuf = m;
 	hdr_addr = buf_addr;
-	if (unlikely(buf_len < dev->vhost_hlen))
+	if (unlikely(buf_len < dev->vhost_hlen)) {
+		memset(&tmp_hdr, 0, sizeof(struct virtio_net_hdr_mrg_rxbuf));
 		hdr = &tmp_hdr;
-	else
+	} else
 		hdr = (struct virtio_net_hdr_mrg_rxbuf *)(uintptr_t)hdr_addr;
 
 	VHOST_LOG_DATA(DEBUG, "(%d) RX: num merge buffers %d\n",