gro: Only reset frag0 when skb can be pulled

gro: Only reset frag0 when skb can be pulled

[Herbert Xu]

Hi:

gro: Only reset frag0 when skb can be pulled

Currently skb_gro_header_slow unconditionally resets frag0 and
frag0_len.  However, when we can't pull on the skb this leaves
the GRO fields in an inconsistent state.

This patch fixes this by only resetting those fields after the
pskb_may_pull test.

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

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index ea6f4aa..a692a7c 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -1679,9 +1679,12 @@ static inline int skb_gro_header_hard(struct sk_buff *skb, unsigned int hlen)
 static inline void *skb_gro_header_slow(struct sk_buff *skb, unsigned int hlen,
 					unsigned int offset)
 {
+	if (!pskb_may_pull(skb, hlen))
+		return NULL;
+
 	NAPI_GRO_CB(skb)->frag0 = NULL;
 	NAPI_GRO_CB(skb)->frag0_len = 0;
-	return pskb_may_pull(skb, hlen) ? skb->data + offset : NULL;
+	return skb->data + offset;
 }
 
 static inline void *skb_gro_mac_header(struct sk_buff *skb)

Cheers,
-- 
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt

Re: gro: Only reset frag0 when skb can be pulled

[David Miller]

From: Herbert Xu <herbert@gondor.hengli.com.au>
Date: Wed, 27 Jul 2011 21:10:08 +0800

> gro: Only reset frag0 when skb can be pulled
> 
> Currently skb_gro_header_slow unconditionally resets frag0 and
> frag0_len.  However, when we can't pull on the skb this leaves
> the GRO fields in an inconsistent state.
> 
> This patch fixes this by only resetting those fields after the
> pskb_may_pull test.
> 
> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

Applied, thanks.

I'll queue this up for -stable too.