[ 3.5.y.z extended stable ] Patch "xen-netfront: reduce gso_max_size to account for max TCP" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    xen-netfront: reduce gso_max_size to account for max TCP

to the linux-3.5.y-queue branch of the 3.5.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.5.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.5.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From 1ba05a195917d1b49765c0fc9ac3d893655a881a Mon Sep 17 00:00:00 2001
From: Wei Liu <wei.liu2 at citrix.com>
Date: Mon, 22 Apr 2013 02:20:41 +0000
Subject: [PATCH] xen-netfront: reduce gso_max_size to account for max TCP
 header

commit 9ecd1a75d977e2e8c48139c7d3efed183f898d94 upstream.

The maximum packet including header that can be handled by netfront / netback
wire format is 65535. Reduce gso_max_size accordingly.

Drop skb and print warning when skb->len > 65535. This can 1) save the effort
to send malformed packet to netback, 2) help spotting misconfiguration of
netfront in the future.

Signed-off-by: Wei Liu <wei.liu2 at citrix.com>
Acked-by: Ian Campbell <ian.campbell at citrix.com>
Signed-off-by: David S. Miller <davem at davemloft.net>
[ luis: backported to 3.5: adjusted context ]
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 drivers/net/xen-netfront.c       | 17 +++++++++++++++--
 include/xen/interface/io/netif.h |  1 +
 2 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/drivers/net/xen-netfront.c b/drivers/net/xen-netfront.c
index 526702d..b88afc7 100644
--- a/drivers/net/xen-netfront.c
+++ b/drivers/net/xen-netfront.c
@@ -36,7 +36,7 @@
 #include <linux/skbuff.h>
 #include <linux/ethtool.h>
 #include <linux/if_ether.h>
-#include <linux/tcp.h>
+#include <net/tcp.h>
 #include <linux/udp.h>
 #include <linux/moduleparam.h>
 #include <linux/mm.h>
@@ -491,6 +491,16 @@ static int xennet_start_xmit(struct sk_buff *skb, struct net_device *dev)
 	unsigned int len = skb_headlen(skb);
 	unsigned long flags;

+	/* If skb->len is too big for wire format, drop skb and alert
+	 * user about misconfiguration.
+	 */
+	if (unlikely(skb->len > XEN_NETIF_MAX_TX_SIZE)) {
+		net_alert_ratelimited(
+			"xennet: skb->len = %u, too big for wire format\n",
+			skb->len);
+		goto drop;
+	}
+
 	frags += DIV_ROUND_UP(offset + len, PAGE_SIZE);
 	if (unlikely(frags > MAX_SKB_FRAGS + 1)) {
 		printk(KERN_ALERT "xennet: skb rides the rocket: %d frags\n",
@@ -1039,7 +1049,8 @@ err:

 static int xennet_change_mtu(struct net_device *dev, int mtu)
 {
-	int max = xennet_can_sg(dev) ? 65535 - ETH_HLEN : ETH_DATA_LEN;
+	int max = xennet_can_sg(dev) ?
+		XEN_NETIF_MAX_TX_SIZE - MAX_TCP_HEADER : ETH_DATA_LEN;

 	if (mtu > max)
 		return -EINVAL;
@@ -1343,6 +1354,8 @@ static struct net_device * __devinit xennet_create_dev(struct xenbus_device *dev
 	SET_ETHTOOL_OPS(netdev, &xennet_ethtool_ops);
 	SET_NETDEV_DEV(netdev, &dev->dev);

+	netif_set_gso_max_size(netdev, XEN_NETIF_MAX_TX_SIZE - MAX_TCP_HEADER);
+
 	np->netdev = netdev;

 	netif_carrier_off(netdev);
diff --git a/include/xen/interface/io/netif.h b/include/xen/interface/io/netif.h
index a36c87a..d4635cd 100644
--- a/include/xen/interface/io/netif.h
+++ b/include/xen/interface/io/netif.h
@@ -65,6 +65,7 @@
 #define _XEN_NETTXF_extra_info		(3)
 #define  XEN_NETTXF_extra_info		(1U<<_XEN_NETTXF_extra_info)

+#define XEN_NETIF_MAX_TX_SIZE 0xFFFF
 struct xen_netif_tx_request {
     grant_ref_t gref;      /* Reference to buffer page */
     uint16_t offset;       /* Offset within buffer page */
--
1.8.1.2