linux-kernel - Re: [ 05/48] x86_64, switch_to(): Load TLS descriptors before switching DS and ES

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Message-ID: <1431693140.6315.109.camel@decadent.org.uk>
Date:	Fri, 15 May 2015 13:32:20 +0100
From:	Ben Hutchings <ben@...adent.org.uk>
To:	Willy Tarreau <w@....eu>
Cc:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	Andy Lutomirski <luto@...capital.net>,
	Andi Kleen <andi@...stfloor.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Ingo Molnar <mingo@...nel.org>
Subject: Re: [ 05/48] x86_64, switch_to(): Load TLS descriptors before
 switching DS and ES

On Fri, 2015-05-15 at 10:05 +0200, Willy Tarreau wrote:
> 2.6.32-longterm review patch.  If anyone has any objections, please let me know.
> 
> ------------------
> 
> From: Andy Lutomirski <luto@...capital.net>
> 
> commit f647d7c155f069c1a068030255c300663516420e upstream.
> 
> Otherwise, if buggy user code points DS or ES into the TLS
> array, they would be corrupted after a context switch.
> 
> This also significantly improves the comments and documents some
> gotchas in the code.
> 
> Before this patch, the both tests below failed.  With this
> patch, the es test passes, although the gsbase test still fails.
[...]

This depends on the changes to FPU/MMX/SSE state management that you
didn't apply to 2.6.32.  Note this comment:

	/* Must be after DS reload */
	unlazy_fpu(prev_p);

Ben.

-- 
Ben Hutchings
It is impossible to make anything foolproof because fools are so ingenious.

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