linux-kernel - Re: [PATCH,TRIVIAL] Fix csum_ipv6

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Date:	Wed, 30 Sep 2009 15:40:44 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Samuel Thibault <samuel.thibault@...-lyon.org>
Cc:	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	"David S. Miller" <davem@...emloft.net>,
	Andi Kleen <andi@...stfloor.org>
Subject: Re: [PATCH,TRIVIAL] Fix csum_ipv6_magic asm memory clobber

On Sat, 26 Sep 2009 21:27:48 +0200
Samuel Thibault <samuel.thibault@...-lyon.org> wrote:

> Just like ip_fast_csum, the assembly snippet in csum_ipv6_magic needs a
> memory clobber, as it is only passed the address of the buffer, not a
> memory reference to the buffer itself.
> 
> Signed-Off-By: Samuel Thibault <samuel.thibault@...-lyon.org>
> Cc: stable@...nel.org
> 
> diff --git a/arch/x86/include/asm/checksum_32.h b/arch/x86/include/asm/checksum_32.h
> index 7c5ef8b..46fc474 100644
> --- a/arch/x86/include/asm/checksum_32.h
> +++ b/arch/x86/include/asm/checksum_32.h
> @@ -161,7 +161,8 @@ static inline __sum16 csum_ipv6_magic(const struct in6_addr *saddr,
>  	    "adcl $0, %0	;\n"
>  	    : "=&r" (sum)
>  	    : "r" (saddr), "r" (daddr),
> -	      "r" (htonl(len)), "r" (htonl(proto)), "0" (sum));
> +	      "r" (htonl(len)), "r" (htonl(proto)), "0" (sum)
> +	    : "memory");
>  
>  	return csum_fold(sum);
>  }

You describe it as "trivial" and also cc stable@...nel.org.  These things
are contradictory!

Maybe backporting it is a good idea from a sleep-soundly-at-night POV. 
I don't know..

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