gso: Stop fraglists from escaping

gso: Stop fraglists from escaping

[Herbert Xu]

Hi:

gso: Stop fraglists from escaping

As it stands skb fraglists can get past the check in dev_queue_xmit
if the skb is marked as GSO.  In particular, if the packet doesn't
have the proper checksums for GSO, but can otherwise be handled by
the underlying device, we will not perform the fraglist check on it
at all.

If the underlying device cannot handle fraglists, then this will
break.

The fix is as simple as moving the fraglist check from the device
check into skb_gso_ok.

This has caused crashes with Xen when used together with GRO which
can generate GSO packets with fraglists.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 5a96a1a..a28daad 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -1856,15 +1856,14 @@ static inline int net_gso_ok(int features, int gso_type)
 
 static inline int skb_gso_ok(struct sk_buff *skb, int features)
 {
-	return net_gso_ok(features, skb_shinfo(skb)->gso_type);
+	return net_gso_ok(features, skb_shinfo(skb)->gso_type) &&
+	       (!skb_shinfo(skb)->frag_list || (features & NETIF_F_FRAGLIST));
 }
 
 static inline int netif_needs_gso(struct net_device *dev, struct sk_buff *skb)
 {
 	return skb_is_gso(skb) &&
 	       (!skb_gso_ok(skb, dev->features) ||
-	        (skb_shinfo(skb)->frag_list &&
-	         !(dev->features & NETIF_F_FRAGLIST)) ||
 		unlikely(skb->ip_summed != CHECKSUM_PARTIAL));
 }
 
Cheers,
-- 
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Email: Herbert Xu ~{PmV>HI~} <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
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Re: gso: Stop fraglists from escaping

[David Miller]

From: Herbert Xu <herbert@gondor.apana.org.au>
Date: Thu, 4 Jun 2009 11:01:21 +1000

> gso: Stop fraglists from escaping
> 
> As it stands skb fraglists can get past the check in dev_queue_xmit
> if the skb is marked as GSO.  In particular, if the packet doesn't
> have the proper checksums for GSO, but can otherwise be handled by
> the underlying device, we will not perform the fraglist check on it
> at all.
> 
> If the underlying device cannot handle fraglists, then this will
> break.
> 
> The fix is as simple as moving the fraglist check from the device
> check into skb_gso_ok.
> 
> This has caused crashes with Xen when used together with GRO which
> can generate GSO packets with fraglists.
> 
> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

Applied to net-next-2.6, thanks Herbert.