On Sun, Sep 18, 2016 at 09:37:19AM +0200, Alexander Gordeev wrote:
> CC: linux-block@vger.kernel.org
> Signed-off-by: Alexander Gordeev <agord...@redhat.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
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