From: Bart Van Assche <bvanassche@acm.org>
To: Tejun Heo <tj@kernel.org>
Cc: Mike Christie <michaelc@cs.wisc.edu>,
linux-scsi <linux-scsi@vger.kernel.org>,
James Bottomley <jbottomley@parallels.com>,
Jens Axboe <axboe@kernel.dk>, Chanho Min <chanho.min@lge.com>
Subject: Re: [PATCH] Fix a use-after-free triggered by device removal
Date: Tue, 11 Sep 2012 08:42:28 +0200 [thread overview]
Message-ID: <504EDD54.9000408@acm.org> (raw)
In-Reply-To: <20120910233843.GI7677@google.com>
On 09/11/12 01:38, Tejun Heo wrote:
> On Fri, Sep 07, 2012 at 08:57:10AM +0200, Bart Van Assche wrote:
>> Also, as far as I can see the functions that can insert a request into
>> the queue (blk_insert_cloned_request(), queue_unplugged(),
>> blk_execute_rq_nowait()) all check whether the queue is dead before
>> inserting a request. That should be sufficient to prevent that new
>> requests are queued after QUEUE_FLAG_DEAD has been set.
>
> Yes, but does that guarantee that none would call into ->request_fn()?
> If so, fine; otherwise, we may need to add another state to prevent
> that.
Good question. As far as I can see calling request_queue.request_fn() is
fine as long as the caller holds a reference on the queue. If e.g.
scsi_request_fn() would get invoked after blk_drain_queue() finished it
will return immediately because it was invoked with an empty request
queue. So we should be fine as long as all blk_run_queue() callers
either hold a reference on the request queue itself or on the sdev that
owns the request queue. As far as I can see if patch
http://marc.info/?l=linux-scsi&m=134453905402413 gets accepted then all
callers in the SCSI core of blk_run_queue() will hold a (direct or
indirect) reference on the request_queue before invoking blk_run_queue()
or __blk_run_queue().
Bart.
next prev parent reply other threads:[~2012-09-11 6:42 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-09-03 14:12 [PATCH] Fix a use-after-free triggered by device removal Bart Van Assche
2012-09-06 16:27 ` Michael Christie
2012-09-06 17:58 ` Bart Van Assche
2012-09-06 18:14 ` Mike Christie
2012-09-06 18:52 ` Bart Van Assche
2012-09-06 23:20 ` Tejun Heo
2012-09-07 6:57 ` Bart Van Assche
2012-09-10 23:38 ` Tejun Heo
2012-09-11 6:42 ` Bart Van Assche [this message]
2012-09-12 20:53 ` Tejun Heo
2012-09-13 7:26 ` Bart Van Assche
2012-09-13 16:53 ` Tejun Heo
2012-09-13 18:27 ` Bart Van Assche
2012-09-13 19:25 ` Tejun Heo
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