linux-kernel - Re: [PATCH v11] NVMe: Convert to blk-mq

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Date:	Thu, 14 Aug 2014 12:20:24 -0600 (MDT)
From:	Keith Busch <keith.busch@...el.com>
To:	Matias Bjorling <m@...rling.me>
cc:	Jens Axboe <axboe@...com>, Keith Busch <keith.busch@...el.com>,
	Matthew Wilcox <willy@...ux.intel.com>,
	"Sam Bradshaw (sbradshaw)" <sbradshaw@...ron.com>,
	LKML <linux-kernel@...r.kernel.org>,
	linux-nvme <linux-nvme@...ts.infradead.org>,
	Christoph Hellwig <hch@...radead.org>,
	Rob Nelson <rlnelson@...gle.com>,
	Ming Lei <tom.leiming@...il.com>
Subject: Re: [PATCH v11] NVMe: Convert to blk-mq

On Thu, 14 Aug 2014, Matias Bjorling wrote:
>> nr_tags must be uninitialized or screwed up somehow, otherwise I don't
>> see how that kmalloc() could warn on being too large. Keith, are you
>> running with slab debugging? Matias, might be worth trying.

The queue's tags were freed in 'blk_mq_map_swqueue' because some queues
weren't mapped to a s/w queue, but the driver has a pointer to that
freed memory, so it's a use-after-free error.

This part in the driver looks different than it used to be in v8 when I
last tested. The nvme_queue used to have a pointer to the 'hctx', but now
it points directly to the 'tags', but it doesn't appear to be very safe.
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