Patch "netvsc: fix incorrect receive checksum offloading" has been added to the 4.8-stable tree

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

netvsc: fix incorrect receive checksum offloading

to the 4.8-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:
netvsc-fix-incorrect-receive-checksum-offloading.patch
and it can be found in the queue-4.8 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Stephen Hemminger <[email protected]>
Date: Sun, 23 Oct 2016 21:32:47 -0700
Subject: netvsc: fix incorrect receive checksum offloading

From: Stephen Hemminger <[email protected]>

[ Upstream commit e52fed7177f74382f742c27de2cc5314790aebb6 ]

The Hyper-V netvsc driver was looking at the incorrect status bits in the checksum info. It was setting the receive checksum unnecessary flag based on the IP header checksum being correct. The checksum flag is skb is about TCP and UDP checksum status. Because of this bug, any packet received with bad TCP checksum would be passed up the stack and to the application causing data corruption. The problem is reproducible via netcat and netem.

This had a side effect of not doing receive checksum offload on IPv6. The driver was also also always doing checksum offload independent of the checksum setting done via ethtool.

---
 drivers/net/hyperv/netvsc_drv.c |   19 +++++++++++--------
 1 file changed, 11 insertions(+), 8 deletions(-)

@@ -624,15 +624,18 @@ static struct sk_buff *netvsc_alloc_recv
 	       packet->total_data_buflen);
 
 	skb->protocol = eth_type_trans(skb, net);
-	if (csum_info) {
-		/* We only look at the IP checksum here.
-		 * Should we be dropping the packet if checksum
-		 * failed? How do we deal with other checksums - TCP/UDP?
-		 */
-		if (csum_info->receive.ip_checksum_succeeded)
+
+	/* skb is already created with CHECKSUM_NONE */
+	skb_checksum_none_assert(skb);
+
+	/*
+	 * In Linux, the IP checksum is always checked.
+	 * Do L4 checksum offload if enabled and present.
+	 */
+	if (csum_info && (net->features & NETIF_F_RXCSUM)) {
+		if (csum_info->receive.tcp_checksum_succeeded ||
+		    csum_info->receive.udp_checksum_succeeded)
 			skb->ip_summed = CHECKSUM_UNNECESSARY;
-		else
-			skb->ip_summed = CHECKSUM_NONE;
 	}
 
 	if (vlan_tci & VLAN_TAG_PRESENT)

Patches currently in stable-queue which might be from [email protected] are

queue-4.8/netvsc-fix-incorrect-receive-checksum-offloading.patch