From mboxrd@z Thu Jan 1 00:00:00 1970 From: Benjamin Block Subject: Re: [PATCH V2 0/2] block/scsi/dm-rq: fix leak of request private data in dm-mpath Date: Fri, 26 Jul 2019 18:20:46 +0200 Message-ID: <20190726162046.GA7523@t480-pf1aa2c2> References: <20190720030637.14447-1-ming.lei@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: 8bit Return-path: Content-Disposition: inline In-Reply-To: <20190720030637.14447-1-ming.lei@redhat.com> Sender: stable-owner@vger.kernel.org To: Ming Lei Cc: Jens Axboe , linux-block@vger.kernel.org, "James E . J . Bottomley" , "Martin K . Petersen" , linux-scsi@vger.kernel.org, "Ewan D . Milne" , Bart Van Assche , Hannes Reinecke , Christoph Hellwig , Mike Snitzer , dm-devel@redhat.com, stable@vger.kernel.org List-Id: linux-scsi@vger.kernel.org Hey Ming Lei, On Sat, Jul 20, 2019 at 11:06:35AM +0800, Ming Lei wrote: > Hi, > > When one request is dispatched to LLD via dm-rq, if the result is > BLK_STS_*RESOURCE, dm-rq will free the request. However, LLD may allocate > private data for this request, so this way will cause memory leak. I am confused about this. Probably because I am not up-to-date with all of blk-mq. But if you free the LLD private data before the request is finished, what is the LLD doing if the request finishes afterwards? Would that not be an automatic use-after-free? > > Add .cleanup_rq() callback and implement it in SCSI for fixing the issue, > since SCSI is the only driver which allocates private requst data in > .queue_rq() path. > > Another use case of this callback is to free the request and re-submit > bios during cpu hotplug when the hctx is dead, see the following link: > > https://lore.kernel.org/linux-block/f122e8f2-5ede-2d83-9ca0-bc713ce66d01@huawei.com/T/#t > > V2: > - run .cleanup_rq() in blk_mq_free_request(), as suggested by Mike -- With Best Regards, Benjamin Block / Linux on IBM Z Kernel Development IBM Systems & Technology Group / IBM Deutschland Research & Development GmbH Vorsitz. AufsR.: Matthias Hartmann / Geschäftsführung: Dirk Wittkopp Sitz der Gesellschaft: Böblingen / Registergericht: AmtsG Stuttgart, HRB 243294