Patch "virtio-net: Add validation for used length" has been added to the 5.10-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    virtio-net: Add validation for used length

to the 5.10-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     virtio-net-add-validation-for-used-length.patch
and it can be found in the queue-5.10 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 5e3f5f30e88b0280da477075d12dfdb9289556df
Author: Xie Yongji <xieyongji@xxxxxxxxxxxxx>
Date:   Mon May 31 21:58:52 2021 +0800

    virtio-net: Add validation for used length
    
    [ Upstream commit ad993a95c508417acdeb15244109e009e50d8758 ]
    
    This adds validation for used length (might come
    from an untrusted device) to avoid data corruption
    or loss.
    
    Signed-off-by: Xie Yongji <xieyongji@xxxxxxxxxxxxx>
    Acked-by: Jason Wang <jasowang@xxxxxxxxxx>
    Link: https://lore.kernel.org/r/20210531135852.113-1-xieyongji@xxxxxxxxxxxxx
    Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 286f836a53bf..e2c6c5675ec6 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -660,6 +660,12 @@ 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) {
@@ -763,6 +769,7 @@ err:
 err_xdp:
 	rcu_read_unlock();
 	stats->xdp_drops++;
+err_len:
 	stats->drops++;
 	put_page(page);
 xdp_xmit:
@@ -816,6 +823,12 @@ 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) {
@@ -943,13 +956,6 @@ 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);
 	curr_skb = head_skb;