[34-longterm 190/196] gro: Only reset frag0 when skb can be pulled

[Paul Gortmaker]

From: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>

                   -------------------
    This is a commit scheduled for the next v2.6.34 longterm release.
    If you see a problem with using this for longterm, please comment.
                   -------------------

commit 17dd759c67f21e34f2156abcf415e1f60605a188 upstream.

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@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Paul Gortmaker <paul.gortmaker@xxxxxxxxxxxxx>
---
 include/linux/netdevice.h |    5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 0af14f2..0899edf 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -1261,9 +1261,12 @@ 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)
-- 
1.7.9.3

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