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From: Dan Schatzberg <schatzberg.dan@gmail.com>
To: Ming Lei <ming.lei@redhat.com>
Cc: "Jens Axboe" <axboe@kernel.dk>,
	linux-block@vger.kernel.org, "Christoph Hellwig" <hch@lst.de>,
	"Michal Koutný" <mkoutny@suse.com>
Subject: Re: [PATCH 6/6] loop: don't add worker into idle list
Date: Thu, 8 Jul 2021 10:41:34 -0400	[thread overview]
Message-ID: <YOcOnlqMMX1K+heE@dschatzberg-fedora-PC0Y6AEN> (raw)
In-Reply-To: <YOaiHLD74VG5I5cD@T590>

On Thu, Jul 08, 2021 at 02:58:36PM +0800, Ming Lei wrote:
> diff --git a/drivers/block/loop.c b/drivers/block/loop.c
> index 146eaa03629b..3cd51bddfec9 100644
> --- a/drivers/block/loop.c
> +++ b/drivers/block/loop.c
> @@ -980,7 +980,6 @@ static struct loop_worker *loop_alloc_or_get_worker(struct loop_device *lo,
>  
>  static void loop_release_worker(struct loop_worker *worker)
>  {
> -	xa_erase(&worker->lo->workers, worker->blkcg_css->id);
>  	css_put(worker->blkcg_css);
>  	kfree(worker);

Another thought - do you need to change the kfree here to kfree_rcu?
I'm concerned about the scenario where loop_queue_work's xa_load finds
the worker and subsequently __loop_free_idle_workers erases and calls
loop_release_worker. If the worker is freed then the subsequent
refcount_inc_not_zero in loop_queue_work would be a use after free.

      parent reply	other threads:[~2021-07-08 14:41 UTC|newest]

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-05 10:26 [PATCH 0/6] loop: cleanup charging io to mem/blkcg Ming Lei
2021-07-05 10:26 ` [PATCH 1/6] loop: clean up blkcg association Ming Lei
2021-07-06  5:51   ` Christoph Hellwig
2021-07-08  7:20     ` Ming Lei
2021-07-05 10:26 ` [PATCH 2/6] loop: conver timer for monitoring idle worker into dwork Ming Lei
2021-07-06  5:52   ` Christoph Hellwig
2021-07-08  7:23     ` Ming Lei
2021-07-05 10:26 ` [PATCH 3/6] loop: add __loop_free_idle_workers() for covering freeing workers in clearing FD Ming Lei
2021-07-05 10:26 ` [PATCH 4/6] loop: improve loop_process_work Ming Lei
2021-07-06  5:54   ` Christoph Hellwig
2021-07-05 10:26 ` [PATCH 5/6] loop: use xarray to store workers Ming Lei
2021-07-05 10:26 ` [PATCH 6/6] loop: don't add worker into idle list Ming Lei
2021-07-06 13:55   ` Dan Schatzberg
2021-07-07  3:19     ` Ming Lei
2021-07-07 13:55       ` Dan Schatzberg
2021-07-08  6:58         ` Ming Lei
2021-07-08 14:16           ` Dan Schatzberg
2021-07-08 15:01             ` Ming Lei
2021-07-08 15:15               ` Dan Schatzberg
2021-07-09  0:49                 ` Ming Lei
2021-07-09 13:47                   ` Dan Schatzberg
2021-07-08 14:41           ` Dan Schatzberg [this message]

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