path: root/net
diff options
authorBen Hutchings <bhutchings@solarflare.com>2012-07-30 15:57:00 +0000
committerDavid S. Miller <davem@davemloft.net>2012-08-02 00:19:17 -0700
commit30b678d844af3305cda5953467005cebb5d7b687 (patch)
tree8e57f081d3a8f8dc44630cee223d2b45ec196e5e /net
parent1a9b4993b70fb1884716902774dc9025b457760d (diff)
net: Allow driver to limit number of GSO segments per skb
A peer (or local user) may cause TCP to use a nominal MSS of as little as 88 (actual MSS of 76 with timestamps). Given that we have a sufficiently prodigious local sender and the peer ACKs quickly enough, it is nevertheless possible to grow the window for such a connection to the point that we will try to send just under 64K at once. This results in a single skb that expands to 861 segments. In some drivers with TSO support, such an skb will require hundreds of DMA descriptors; a substantial fraction of a TX ring or even more than a full ring. The TX queue selected for the skb may stall and trigger the TX watchdog repeatedly (since the problem skb will be retried after the TX reset). This particularly affects sfc, for which the issue is designated as CVE-2012-3412. Therefore: 1. Add the field net_device::gso_max_segs holding the device-specific limit. 2. In netif_skb_features(), if the number of segments is too high then mask out GSO features to force fall back to software GSO. Signed-off-by: Ben Hutchings <bhutchings@solarflare.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net')
1 files changed, 4 insertions, 0 deletions
diff --git a/net/core/dev.c b/net/core/dev.c
index 0cb3fe8d8e72..f91abf800161 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -2134,6 +2134,9 @@ netdev_features_t netif_skb_features(struct sk_buff *skb)
__be16 protocol = skb->protocol;
netdev_features_t features = skb->dev->features;
+ if (skb_shinfo(skb)->gso_segs > skb->dev->gso_max_segs)
+ features &= ~NETIF_F_GSO_MASK;
if (protocol == htons(ETH_P_8021Q)) {
struct vlan_ethhdr *veh = (struct vlan_ethhdr *)skb->data;
protocol = veh->h_vlan_encapsulated_proto;
@@ -5986,6 +5989,7 @@ struct net_device *alloc_netdev_mqs(int sizeof_priv, const char *name,
dev_net_set(dev, &init_net);
dev->gso_max_size = GSO_MAX_SIZE;
+ dev->gso_max_segs = GSO_MAX_SEGS;

Privacy Policy