linux-kernel - Re: [PATCH] powerpc: fix csum_ipv6_magic() on little endian platforms

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Date:   Mon, 17 Sep 2018 14:27:11 +0200
From:   Christophe LEROY <christophe.leroy@....fr>
To:     Michael Ellerman <mpe@...erman.id.au>
Cc:     Xin Long <lucien.xin@...il.com>, benh@...nel.crashing.org,
        paulus@...ba.org, jishi@...hat.com,
        LKML <linux-kernel@...r.kernel.org>,
        linuxppc-dev@...ts.ozlabs.org, stable@...r.kernel.org,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        David Miller <davem@...emloft.net>
Subject: Re: [PATCH] powerpc: fix csum_ipv6_magic() on little endian platforms

Hi Michael,

Le 10/09/2018 à 16:28, Xin Long a écrit :
> On Mon, Sep 10, 2018 at 2:09 PM Christophe Leroy
> <christophe.leroy@....fr> wrote:
>>
>> On little endian platforms, csum_ipv6_magic() keeps len and proto in
>> CPU byte order. This generates a bad results leading to ICMPv6 packets
>> from other hosts being dropped by powerpc64le platforms.
>>
>> In order to fix this, len and proto should be converted to network
>> byte order ie bigendian byte order. However checksumming 0x12345678
>> and 0x56341278 provide the exact same result so it is enough to
>> rotate the sum of len and proto by 1 byte.
>>
>> PPC32 only support bigendian so the fix is needed for PPC64 only
>>
>> Fixes: e9c4943a107b ("powerpc: Implement csum_ipv6_magic in assembly")
>> Reported-by: Jianlin Shi <jishi@...hat.com>
>> Reported-by: Xin Long <lucien.xin@...il.com>
>> Cc: <stable@...r.kernel.org> # 4.18+
>> Signed-off-by: Christophe Leroy <christophe.leroy@....fr>
>> ---
>>   arch/powerpc/lib/checksum_64.S | 3 +++
>>   1 file changed, 3 insertions(+)
>>
>> diff --git a/arch/powerpc/lib/checksum_64.S b/arch/powerpc/lib/checksum_64.S
>> index 886ed94b9c13..2a68c43e13f5 100644
>> --- a/arch/powerpc/lib/checksum_64.S
>> +++ b/arch/powerpc/lib/checksum_64.S
>> @@ -443,6 +443,9 @@ _GLOBAL(csum_ipv6_magic)
>>          addc    r0, r8, r9
>>          ld      r10, 0(r4)
>>          ld      r11, 8(r4)
>> +#ifndef CONFIG_CPU_BIG_ENDIAN
>> +       rotldi  r5, r5, 8
>> +#endif
>>          adde    r0, r0, r10
>>          add     r5, r5, r7
>>          adde    r0, r0, r11
>> --
>> 2.13.3
>>
> Tested-by: Xin Long <lucien.xin@...il.com>
> 

Could you take this fix for 4.19 ?

Unless someone takes it through the netdev tree ?

Thanks
Christophe