Re: [PATCH v4] virtio-net: Add validation for used length

---
  drivers/net/virtio_net.c | 20 +++++++++++++-------
  1 file changed, 13 insertions(+), 7 deletions(-)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 073fec4c0df1..ed969b65126e 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c

@@ -730,6 +730,12 @@ static struct sk_buff *receive_small(struct net_device *dev,
  	len -= vi->hdr_len;
  	stats->bytes += len;
  
+	if (unlikely(len > GOOD_PACKET_LEN)) {
+		pr_debug("%s: rx error: len %u exceeds max size %d\n",
+			 dev->name, len, GOOD_PACKET_LEN);
+		dev->stats.rx_length_errors++;
+		goto err_len;
+	}
  	rcu_read_lock();
  	xdp_prog = rcu_dereference(rq->xdp_prog);
  	if (xdp_prog) {

@@ -833,6 +839,7 @@ static struct sk_buff *receive_small(struct net_device *dev,
  err_xdp:
  	rcu_read_unlock();
  	stats->xdp_drops++;
+err_len:
  	stats->drops++;
  	put_page(page);
  xdp_xmit:

@@ -886,6 +893,12 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
  	head_skb = NULL;
  	stats->bytes += len - vi->hdr_len;
  
+	if (unlikely(len > truesize)) {
+		pr_debug("%s: rx error: len %u exceeds truesize %lu\n",
+			 dev->name, len, (unsigned long)ctx);
+		dev->stats.rx_length_errors++;
+		goto err_skb;
+	}
  	rcu_read_lock();
  	xdp_prog = rcu_dereference(rq->xdp_prog);
  	if (xdp_prog) {

@@ -1012,13 +1025,6 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
  	}
  	rcu_read_unlock();
  
-	if (unlikely(len > truesize)) {
-		pr_debug("%s: rx error: len %u exceeds truesize %lu\n",
-			 dev->name, len, (unsigned long)ctx);
-		dev->stats.rx_length_errors++;
-		goto err_skb;
-	}
-
  	head_skb = page_to_skb(vi, rq, page, offset, len, truesize, !xdp_prog,
  			       metasize, !!headroom);
  	curr_skb = head_skb;