This is a note to let you know that I've just added the patch titled
powerpc/64: Fix checksum folding in csum_tcpudp_nofold and ip_fast_csum_nofold
to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
powerpc-64-fix-checksum-folding-in-csum_tcpudp_nofold-and-ip_fast_csum_nofold.patch
and it can be found in the queue-4.9 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From b492f7e4e07a28e706db26cf4943bb0911435426 Mon Sep 17 00:00:00 2001
From: Paul Mackerras <paulus@xxxxxxxxxx>
Date: Thu, 3 Nov 2016 16:10:55 +1100
Subject: powerpc/64: Fix checksum folding in csum_tcpudp_nofold and ip_fast_csum_nofold
From: Paul Mackerras <paulus@xxxxxxxxxx>
commit b492f7e4e07a28e706db26cf4943bb0911435426 upstream.
These functions compute an IP checksum by computing a 64-bit sum and
folding it to 32 bits (the "nofold" in their names refers to folding
down to 16 bits). However, doing (u32) (s + (s >> 32)) is not
sufficient to fold a 64-bit sum to 32 bits correctly. The addition
can produce a carry out from bit 31, which needs to be added in to
the sum to produce the correct result.
To fix this, we copy the from64to32() function from lib/checksum.c
and use that.
Signed-off-by: Paul Mackerras <paulus@xxxxxxxxxx>
Signed-off-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/powerpc/include/asm/checksum.h | 17 ++++++++++++-----
1 file changed, 12 insertions(+), 5 deletions(-)
--- a/arch/powerpc/include/asm/checksum.h
+++ b/arch/powerpc/include/asm/checksum.h
@@ -53,17 +53,25 @@ static inline __sum16 csum_fold(__wsum s
return (__force __sum16)(~((__force u32)sum + tmp) >> 16);
}
+static inline u32 from64to32(u64 x)
+{
+ /* add up 32-bit and 32-bit for 32+c bit */
+ x = (x & 0xffffffff) + (x >> 32);
+ /* add up carry.. */
+ x = (x & 0xffffffff) + (x >> 32);
+ return (u32)x;
+}
+
static inline __wsum csum_tcpudp_nofold(__be32 saddr, __be32 daddr, __u32 len,
__u8 proto, __wsum sum)
{
#ifdef __powerpc64__
- unsigned long s = (__force u32)sum;
+ u64 s = (__force u32)sum;
s += (__force u32)saddr;
s += (__force u32)daddr;
s += proto + len;
- s += (s >> 32);
- return (__force __wsum) s;
+ return (__force __wsum) from64to32(s);
#else
__asm__("\n\
addc %0,%0,%1 \n\
@@ -123,8 +131,7 @@ static inline __wsum ip_fast_csum_nofold
for (i = 0; i < ihl - 1; i++, ptr++)
s += *ptr;
- s += (s >> 32);
- return (__force __wsum)s;
+ return (__force __wsum)from64to32(s);
#else
__wsum sum, tmp;
Patches currently in stable-queue which might be from paulus@xxxxxxxxxx are
queue-4.9/powerpc-64-fix-checksum-folding-in-csum_tcpudp_nofold-and-ip_fast_csum_nofold.patch