linux-kernel - Re: [PATCH] x86 spinlock: Fix memory corruption on completing completions

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Message-ID: <54D8AD85.1070409@linux.vnet.ibm.com>
Date:	Mon, 09 Feb 2015 18:22:21 +0530
From:	Raghavendra K T <raghavendra.kt@...ux.vnet.ibm.com>
To:	Peter Zijlstra <peterz@...radead.org>
CC:	Jeremy Fitzhardinge <jeremy@...p.org>, tglx@...utronix.de,
	mingo@...hat.com, hpa@...or.com, torvalds@...ux-foundation.org,
	konrad.wilk@...cle.com, pbonzini@...hat.com,
	paulmck@...ux.vnet.ibm.com, waiman.long@...com, davej@...hat.com,
	oleg@...hat.com, x86@...nel.org, paul.gortmaker@...driver.com,
	ak@...ux.intel.com, jasowang@...hat.com,
	linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
	virtualization@...ts.linux-foundation.org,
	xen-devel@...ts.xenproject.org, riel@...hat.com,
	borntraeger@...ibm.com, akpm@...ux-foundation.org,
	a.ryabinin@...sung.com, sasha.levin@...cle.com
Subject: Re: [PATCH] x86 spinlock: Fix memory corruption on completing completions

On 02/09/2015 05:32 PM, Peter Zijlstra wrote:
> On Mon, Feb 09, 2015 at 03:04:22PM +0530, Raghavendra K T wrote:
>> So we have 3 choices,
>> 1. xadd
>> 2. continue with current approach.
>> 3. a read before unlock and also after that.
>
> For the truly paranoid we have probe_kernel_address(), suppose the lock
> was in module space and the module just got unloaded under us.
>

Thanks.. Good idea, How costly is it?
atleast we could do probe_kernel_address() and check the value of
slowpath flag if people as us to address invalid read problem.

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