linux-kernel - Re: [PATCH 09/14] blk-mq: Move duplicating code to blk_mq_exit

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Date:   Mon, 19 Sep 2016 10:57:19 -0700
From:   Omar Sandoval <osandov@...ndov.com>
To:     Alexander Gordeev <agordeev@...hat.com>
Cc:     linux-kernel@...r.kernel.org, linux-block@...r.kernel.org
Subject: Re: [PATCH 09/14] blk-mq: Move duplicating code to blk_mq_exit_hctx()

On Sun, Sep 18, 2016 at 09:37:19AM +0200, Alexander Gordeev wrote:
> CC: linux-block@...r.kernel.org
> Signed-off-by: Alexander Gordeev <agordeev@...hat.com>
> ---
>  block/blk-mq.c | 14 +++++---------
>  1 file changed, 5 insertions(+), 9 deletions(-)
> 
> diff --git a/block/blk-mq.c b/block/blk-mq.c
> index 3efb700..cd32a08 100644
> --- a/block/blk-mq.c
> +++ b/block/blk-mq.c
> @@ -1678,6 +1678,10 @@ static void blk_mq_exit_hctx(struct request_queue *q,
>  	blk_mq_unregister_cpu_notifier(&hctx->cpu_notifier);
>  	blk_free_flush_queue(hctx->fq);
>  	blk_mq_free_bitmap(&hctx->ctx_map);
> +
> +	free_cpumask_var(hctx->cpumask);
> +	kfree(hctx->ctxs);
> +	kfree(hctx);
>  }
>  
>  static void blk_mq_exit_hw_queues(struct request_queue *q,
> @@ -1686,12 +1690,8 @@ static void blk_mq_exit_hw_queues(struct request_queue *q,
>  	struct blk_mq_hw_ctx *hctx;
>  	unsigned int i;
>  
> -	queue_for_each_hw_ctx(q, hctx, i) {
> +	queue_for_each_hw_ctx(q, hctx, i)
>  		blk_mq_exit_hctx(q, set, hctx, i);
> -		free_cpumask_var(hctx->cpumask);
> -		kfree(hctx->ctxs);
> -		kfree(hctx);
> -	}
>  
>  	q->nr_hw_queues = 0;
>  }
> @@ -2018,12 +2018,8 @@ static void blk_mq_realloc_hw_ctxs(struct blk_mq_tag_set *set,
>  				set->tags[j] = NULL;
>  			}
>  			blk_mq_exit_hctx(q, set, hctx, j);
> -			free_cpumask_var(hctx->cpumask);
>  			kobject_put(&hctx->kobj);

Now this hctx->kobj will be a use-after-free since we just kfreed hctx
in blk_mq_exit_hctx().

> -			kfree(hctx->ctxs);
> -			kfree(hctx);
>  			hctxs[j] = NULL;
> -
>  		}
>  	}
>  	q->nr_hw_queues = i;
> -- 
> 1.8.3.1
> 
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-- 
Omar