Patchwork [net-next,v3] netfilter: Correct calculation using skb->tail and skb-network_header

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Submitter Simon Horman
Date May 31, 2013, 2:39 a.m.
Message ID <1369967969-32375-1-git-send-email-horms@verge.net.au>
Download mbox | patch
Permalink /patch/247829/
State Not Applicable
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Comments

Simon Horman - May 31, 2013, 2:39 a.m.
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@canb.auug.org.au>
Reported-by: Chen Gang <gang.chen@asianux.com>
Signed-off-by: Simon Horman <horms@verge.net.au>

--
v3
* Add net-next to subject prefix

v2
* Use skb_tail_pointer() to ensure the tail portion of the calculation is
  always a pointer - it is not if NET_SKBUFF_DATA_USES_OFFSET is not set.
---
 net/netfilter/nf_nat_helper.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
David Miller - May 31, 2013, 11:38 p.m.
From: Simon Horman <horms@verge.net.au>
Date: Fri, 31 May 2013 11:39:29 +0900

> 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@canb.auug.org.au>
> Reported-by: Chen Gang <gang.chen@asianux.com>
> Signed-off-by: Simon Horman <horms@verge.net.au>

I've applied this directly to net-next, thanks Simon.
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Chen Gang - June 3, 2013, 9:06 a.m.
On 05/31/2013 10:39 AM, Simon Horman wrote:
> 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@canb.auug.org.au>
> Reported-by: Chen Gang <gang.chen@asianux.com>
> Signed-off-by: Simon Horman <horms@verge.net.au>
> 
> --
> v3
> * Add net-next to subject prefix
> 
> v2
> * Use skb_tail_pointer() to ensure the tail portion of the calculation is
>   always a pointer - it is not if NET_SKBUFF_DATA_USES_OFFSET is not set.

Thanks.

Patch

diff --git a/net/netfilter/nf_nat_helper.c b/net/netfilter/nf_nat_helper.c
index 5fea563..85e20a9 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_pointer(skb) - (skb_network_header(skb) + dataoff +
 			     match_offset + match_len));
 
 	/* insert data from buffer */