linux-kernel - Re: [PATCH -next v2] block: fix blktrace debugfs entries leak

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Message-ID: <20230601061858.GA24071@lst.de>
Date:   Thu, 1 Jun 2023 08:18:58 +0200
From:   Christoph Hellwig <hch@....de>
To:     Yu Kuai <yukuai1@...weicloud.com>
Cc:     Christoph Hellwig <hch@....de>, axboe@...nel.dk,
        linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
        yi.zhang@...wei.com, yangerkun@...wei.com,
        "yukuai (C)" <yukuai3@...wei.com>
Subject: Re: [PATCH -next v2] block: fix blktrace debugfs entries leak

On Thu, Jun 01, 2023 at 09:50:22AM +0800, Yu Kuai wrote:
> Hi, Christoph
>
> 在 2023/05/31 20:44, Christoph Hellwig 写道:
>> I like where this is going, but did you check that this doesn't
>> introduce a potential crash with the current /dev/sg based blktrace?
>
> I just start to look at how /dev/sg is created and destroyed, however,
> I'm confused here, do you mean that the added blk_trace_shutdown() here
> might cause that /dev/sg blktrace to access freed momory or NULL
> pointer?

Yes.  Given that __blk_trace_remove clears out q->blk_trace and
frees the blk trace structure I'm worried about that.