netdev - [PATCH] netfilter: Correct calculation using skb->tail and skb-network

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Message-Id: <1369958133-20576-1-git-send-email-horms@verge.net.au>
Date:	Fri, 31 May 2013 08:55:33 +0900
From:	Simon Horman <horms@...ge.net.au>
To:	Pablo Neira Ayuso <pablo@...filter.org>,
	David Miller <davem@...emloft.net>
Cc:	netdev@...r.kernel.org, netfilter-devel@...r.kernel.org,
	Chen Gang <gang.chen@...anux.com>,
	Simon Horman <horms@...ge.net.au>
Subject: [PATCH] netfilter: Correct calculation using skb->tail and skb-network_header

This corrects an regression introduced by "net: Use 16bits for *_headers
fields of struct skbuff" when NET_SKBUFF_DATA_USES_OFFSET is not set. In
that case skb->tail will be a pointer whereas skb->network_header
will be an offset from head. This is corrected by using wrappers that
ensure that calculations are always made using pointers.

Reported-by: Stephen Rothwell <sfr@...b.auug.org.au>
Reported-by: Chen Gang <gang.chen@...anux.com>
Signed-off-by: Simon Horman <horms@...ge.net.au>
---
 net/netfilter/nf_nat_helper.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/netfilter/nf_nat_helper.c b/net/netfilter/nf_nat_helper.c
index 5fea563..fdbdfec 100644
--- a/net/netfilter/nf_nat_helper.c
+++ b/net/netfilter/nf_nat_helper.c
@@ -104,7 +104,7 @@ static void mangle_contents(struct sk_buff *skb,
 	/* move post-replacement */
 	memmove(data + match_offset + rep_len,
 		data + match_offset + match_len,
-		skb->tail - (skb->network_header + dataoff +
+		skb->tail - (skb_network_header(skb) + dataoff +
 			     match_offset + match_len));
 
 	/* insert data from buffer */
-- 
1.7.10.4

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