linux-kernel - Re: [PATCH] blk-mq: use after free when freeing tag sets

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Date:	Fri, 16 Oct 2015 13:56:31 -0400
From:	Sasha Levin <sasha.levin@...cle.com>
To:	axboe@...nel.dk
CC:	keith.busch@...el.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] blk-mq: use after free when freeing tag sets

ping?

On 10/02/2015 09:40 PM, Sasha Levin wrote:
> Commit f26cdc853 ("blk-mq: Shared tag enhancements") has introduced a use after
> free where it tried to free the cpumask var out of the tag set but the tag set
> was already freed by blk_mq_free_rq_map().
> 
> Signed-off-by: Sasha Levin <sasha.levin@...cle.com>
> ---
>  block/blk-mq-tag.c |    1 +
>  block/blk-mq.c     |    7 ++-----
>  2 files changed, 3 insertions(+), 5 deletions(-)
> 
> diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c
> index f6020c6..c03eeb8 100644
> --- a/block/blk-mq-tag.c
> +++ b/block/blk-mq-tag.c
> @@ -628,6 +628,7 @@ void blk_mq_free_tags(struct blk_mq_tags *tags)
>  {
>  	bt_free(&tags->bitmap_tags);
>  	bt_free(&tags->breserved_tags);
> +	free_cpumask_var(tags->cpumask);
>  	kfree(tags);
>  }
>  
> diff --git a/block/blk-mq.c b/block/blk-mq.c
> index 5692c15..197a615 100644
> --- a/block/blk-mq.c
> +++ b/block/blk-mq.c
> @@ -2270,12 +2270,9 @@ void blk_mq_free_tag_set(struct blk_mq_tag_set *set)
>  {
>  	int i;
>  
> -	for (i = 0; i < set->nr_hw_queues; i++) {
> -		if (set->tags[i]) {
> +	for (i = 0; i < set->nr_hw_queues; i++)
> +		if (set->tags[i])
>  			blk_mq_free_rq_map(set, set->tags[i], i);
> -			free_cpumask_var(set->tags[i]->cpumask);
> -		}
> -	}
>  
>  	kfree(set->tags);
>  	set->tags = NULL;
> 

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