linux-kernel - Re: [PATCH] blk-mq: Fix a recently introduced scsi-mq regression

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Date:	Thu, 29 Jan 2015 19:39:14 +0800
From:	Ming Lei <ming.lei@...onical.com>
To:	Bart Van Assche <bart.vanassche@...disk.com>
Cc:	Jens Axboe <axboe@...nel.dk>, Sasha Levin <sasha.levin@...cle.com>,
	Christoph Hellwig <hch@....de>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] blk-mq: Fix a recently introduced scsi-mq regression

Hi Bart,

On Thu, Jan 29, 2015 at 7:27 PM, Bart Van Assche
<bart.vanassche@...disk.com> wrote:
> On 01/29/15 00:52, Ming Lei wrote:
>> On Thu, Jan 29, 2015 at 2:28 AM, Bart Van Assche
>> <bart.vanassche@...disk.com> wrote:
>>> This patch fixes a use-after-free that was introduced via patch
>>> "blk-mq: fix hctx/ctx kobject use-after-free" (commit
>>> 76d697d10769; kernel v3.19-rc4) and fixes the following crash:
>>
>> Sorry, my fault, I shouldn't have linked mq's release with mq_kobj,
>> which may be released before running blk_cleanup_queue().
>>
>> Another approach may be to revert the faulty commit and release all
>> mq stuff in request queue's release handler(blk_release_queue)
>> which should be more safe and simple.
>
> Hello Ming,
>
> How important is the patch with commit ID 76d697d10769 ? Does it have to
> be included in kernel v3.19 or can it be postponed until kernel v3.19.1
> or kernel v3.19.2 ? If so, how about reverting that patch for kernel

The patch has been in linus tree, but it isn't marked as -stable.

> v3.19 and sending a reworked patch to Jens with a "Cc: stable" tag after
> the release of kernel v3.19 ? That last patch will then get included in
> a stable version of kernel v3.19.

Anyway, it need to be fixed, either reverted or a new patch.

I will post out one revert and another fix candidate, and let's
discuss further.


Thanks,
Ming Lei
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