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From: Benjamin Block <>
To: Ming Lei <>
Cc: Jens Axboe <>,,
	"James E . J . Bottomley" <>,
	"Martin K . Petersen" <>,, "Ewan D . Milne" <>,
	Bart Van Assche <>,
	Hannes Reinecke <>, Christoph Hellwig <>,
	Mike Snitzer <>,,
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	[thread overview]
Message-ID: <20190726162046.GA7523@t480-pf1aa2c2> (raw)
In-Reply-To: <>

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:
> 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

  parent reply	other threads:[~2019-07-26 16:20 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-07-20  3:06 [PATCH V2 0/2] block/scsi/dm-rq: fix leak of request private data in dm-mpath Ming Lei
2019-07-20  3:06 ` [PATCH V2 1/2] blk-mq: add callback of .cleanup_rq Ming Lei
2019-07-22 16:51   ` Bart Van Assche
2019-07-23  1:00     ` Ming Lei
2019-07-20  3:06 ` [PATCH V2 2/2] scsi: implement .cleanup_rq callback Ming Lei
2019-07-22 15:40   ` Bart Van Assche
2019-07-23  1:03     ` Ming Lei
     [not found]   ` <20190725104629.GC3640@shao2-debian>
2019-07-27  2:15     ` [scsi] ae86a1c553: BUG:kernel_NULL_pointer_dereference,address Ming Lei
2019-07-26 16:20 ` Benjamin Block [this message]
2019-07-27  2:12   ` [PATCH V2 0/2] block/scsi/dm-rq: fix leak of request private data in dm-mpath Ming Lei

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