linux-kernel - Re: [PATCH] blktrace: Fix uaf in blk_trace access after removing by sysfs

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Date:   Wed, 22 Sep 2021 06:21:35 +0100
From:   Christoph Hellwig <hch@...radead.org>
To:     Zhihao Cheng <chengzhihao1@...wei.com>
Cc:     axboe@...nel.dk, rostedt@...dmis.org, mingo@...hat.com,
        acme@...hat.com, linux-block@...r.kernel.org,
        linux-kernel@...r.kernel.org, yukuai3@...wei.com
Subject: Re: [PATCH] blktrace: Fix uaf in blk_trace access after removing by
 sysfs

On Fri, Sep 10, 2021 at 05:21:20PM +0800, Zhihao Cheng wrote:
> +		else {
> +			/*
> +			 * Don't remove blk_trace under running state, in
> +			 * case triggering use-after-free in function
> +			 * __blk_add_trace().
> +			 */
> +			if (bt->trace_state != Blktrace_running)
> +				ret = blk_trace_remove_queue(q);
> +			else
> +				ret = -EBUSY;
> +		}
>  		goto out_unlock_bdev;

So who is going to eventually call blk_trace_free in this case?

Also Having the check in blk_trace_remove_queue would seem a little
cleaner.