xen-netfront: reduce gso_max_size to account for max TCP header
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>
diff --git a/drivers/net/xen-netfront.c b/drivers/net/xen-netfront.c
index 1bb2e20..1db10141 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>
@@ -547,6 +547,16 @@
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;
+ }
+
slots = DIV_ROUND_UP(offset + len, PAGE_SIZE) +
xennet_count_skb_frag_slots(skb);
if (unlikely(slots > MAX_SKB_FRAGS + 1)) {
@@ -1058,7 +1068,8 @@
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;
@@ -1362,6 +1373,8 @@
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);