linux-kernel - Re: [PATCH] blk-mq: Avoid race condition with uninitialized requests

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Message-ID: <54202F75.8080401@kernel.dk>
Date:	Mon, 22 Sep 2014 08:17:25 -0600
From:	Jens Axboe <axboe@...nel.dk>
To:	Christian Borntraeger <borntraeger@...ibm.com>,
	tom.leiming@...il.com
CC:	David Hildenbrand <dahi@...ux.vnet.ibm.com>, kvm@...r.kernel.org,
	stable@...r.kernel.org, rusty@...tcorp.com.au,
	virtualization@...ts.linux-foundation.org, mst@...hat.com,
	linux-kernel@...r.kernel.org, ppinatti@...ux.vnet.ibm.com
Subject: Re: [PATCH] blk-mq: Avoid race condition with uninitialized requests

On 2014-09-22 08:15, Christian Borntraeger wrote:
> On 09/18/2014 11:04 AM, David Hildenbrand wrote:
>> This patch should fix the bug reported in https://lkml.org/lkml/2014/9/11/249.
>>
>> We have to initialize at least the atomic_flags and the cmd_flags when
>> allocating storage for the requests.
>>
>> Otherwise blk_mq_timeout_check() might dereference uninitialized pointers when
>> racing with the creation of a request.
>>
>> Also move the reset of cmd_flags for the initializing code to the point where a
>> request is freed. So we will never end up with pending flush request indicators
>> that might trigger dereferences of invalid pointers in blk_mq_timeout_check().
>>
>> Cc: stable@...r.kernel.org
>> Signed-off-by: David Hildenbrand <dahi@...ux.vnet.ibm.com>
>
> Acked-by: Christian Borntraeger <borntraeger@...ibm.com>
>
> Can you please add
> Reported-by: Paulo De Rezende Pinatti <ppinatti@...ux.vnet.ibm.com>
> Tested-by: Paulo De Rezende Pinatti <ppinatti@...ux.vnet.ibm.com>
>
> as Paulo did the testing work?
>
> We thing this patch is fine and should go upstream.

I might have to pick'n rebase the series, in which case I'll add it. But 
I already queued it up last week, so if I don't, then I can't easily add 
it. I wish the git notes wasn't such a horrible and unusable hack, so we 
had a chance to annotate commits without having to rewrite history...

-- 
Jens Axboe

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