[064/141] xen-netfront: reduce gso_max_size to account for max TCP header

Steven Rostedt
2013-07-03T18:44:28Z

[-- Attachment #1: 0064-xen-netfront-reduce-gso_max_size-to-account-for-max-.patch --]
[-- Type: text/plain, Size: 2973 bytes --]

3.6.11.6 stable review patch.
If anyone has any objections, please let me know.

------------------

From: Wei Liu <wei.liu2@citrix.com>

[ Upstream commit 9ecd1a75d977e2e8c48139c7d3efed183f898d94 ]

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@citrix.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
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 650f79a..ecac034 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",
@@ -1026,7 +1036,8 @@ 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;
@@ -1330,6 +1341,8 @@ 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 */
--
1.7.10.4