Patchwork [RFC,1/4] netfilter: ip6t_NPT: Fix checksuming.

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Submitter YOSHIFUJI Hideaki / 吉藤英明
Date Jan. 26, 2013, 6:37 p.m.
Message ID <5104227C.3030306@linux-ipv6.org>
Download mbox | patch
Permalink /patch/215923/
State Accepted
Headers show

Comments

YOSHIFUJI Hideaki / 吉藤英明 - Jan. 26, 2013, 6:37 p.m.
Cast __wsum from/to __sum16 is wrong.  Instead, apply appropriate
conversion function: csum_unfold() or csum_fold().

Signed-off-by: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>
---
 net/ipv6/netfilter/ip6t_NPT.c |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)
Pablo Neira - Feb. 7, 2013, 6:14 p.m.
On Sun, Jan 27, 2013 at 03:37:48AM +0900, YOSHIFUJI Hideaki wrote:
> Cast __wsum from/to __sum16 is wrong.  Instead, apply appropriate
> conversion function: csum_unfold() or csum_fold().

Applied.

I have mangled this patch by collapsing Ulrich's:

http://patchwork.ozlabs.org/patch/216563/

And I have added this to the description:

    [ The original patch has been modified to undo the final ~ that
      csum_fold returns. We only need to fold the 32-bit word that
      results from the checksum calculation into a 16-bit to ensure
      that the original subnet is restored appropriately. Spotted by
      Ulrich Weber. ]

Thanks.
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Patch

diff --git a/net/ipv6/netfilter/ip6t_NPT.c b/net/ipv6/netfilter/ip6t_NPT.c
index 7302b0b..3ff281b 100644
--- a/net/ipv6/netfilter/ip6t_NPT.c
+++ b/net/ipv6/netfilter/ip6t_NPT.c
@@ -30,7 +30,7 @@  static int ip6t_npt_checkentry(const struct xt_tgchk_param *par)
 				(__force __wsum)npt->dst_pfx.in6.s6_addr16[i]);
 	}
 
-	npt->adjustment = (__force __sum16) csum_sub(src_sum, dst_sum);
+	npt->adjustment = csum_fold(csum_sub(src_sum, dst_sum));
 	return 0;
 }
 
@@ -66,8 +66,8 @@  static bool ip6t_npt_map_pfx(const struct ip6t_npt_tginfo *npt,
 			return false;
 	}
 
-	sum = (__force __sum16) csum_add((__force __wsum)addr->s6_addr16[idx],
-			 npt->adjustment);
+	sum = csum_fold(csum_add(csum_unfold((__force __sum16)addr->s6_addr16[idx]),
+				 csum_unfold(npt->adjustment)));
 	if (sum == CSUM_MANGLED_0)
 		sum = 0;
 	*(__force __sum16 *)&addr->s6_addr16[idx] = sum;