linux-kernel - Re: [PATCH] tcp: fix tcp_fastopen unaligned access complaints on sparc

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Date:   Thu, 12 Jan 2017 16:18:52 -0500 (EST)
From:   David Miller <davem@...emloft.net>
To:     shannon.nelson@...cle.com
Cc:     eric.dumazet@...il.com, rob.gardner@...cle.com,
        netdev@...r.kernel.org, sparclinux@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] tcp: fix tcp_fastopen unaligned access complaints on
 sparc

From: Shannon Nelson <shannon.nelson@...cle.com>
Date: Thu, 12 Jan 2017 12:56:08 -0800

> 
> 
> On 1/12/2017 12:41 PM, David Miller wrote:
>> From: Shannon Nelson <shannon.nelson@...cle.com>
>> Date: Thu, 12 Jan 2017 12:30:38 -0800
>>
>>> On 1/12/2017 12:25 PM, Eric Dumazet wrote:
>>>> On Thu, 2017-01-12 at 13:15 -0700, Rob Gardner wrote:
>>>>
>>>>>
>>>>> I suspect that someplace, somebody is casting val to an int * or
>>>>> something like that.
>>>>
>>>> Then that would be the bug. Can we root cause this please ?
>>>>
>>>>
>>>
>>> Look in net/ipv4/tcp_fastopen.c:tcp_fastopen_cookie_gen() for the line
>>>
>>> 	 struct in6_addr *buf = (struct in6_addr *) tmp.val;
>>
>> Oh yeah, that's it.  I didn't notice that at all.
>>
> 
> It looked to me like swapping the data fields would be the easiest and
> least impactive way to fix this.  I didn't want to mess with the
> logic. I'm certainly open to other suggestions.

Given the nature of the problem, your fix is probably fine.

Eric, any objections?