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From: Tejun Heo <tj@kernel.org>
To: Yufen Yu <yuyufen@huawei.com>
Cc: axboe@kernel.dk, linux-block@vger.kernel.org, jack@suse.cz,
	bvanassche@acm.org
Subject: Re: [PATCH] bdi: fix use-after-free for bdi device
Date: Wed, 12 Feb 2020 16:33:44 -0500	[thread overview]
Message-ID: <20200212213344.GE80993@mtj.thefacebook.com> (raw)
In-Reply-To: <b7cd6193-586b-f4e0-9a5d-cc961eafaf81@huawei.com>

Hello, Yufen.

On Tue, Feb 11, 2020 at 09:57:44PM +0800, Yufen Yu wrote:
> There is another simple way to fix the problem.
> 
> Since blkg_dev_name() have been coverd by rcu_read_lock/unlock(),
> we can wait all rcu reader to finish before free 'bdi->dev' to avoid use-after-free.
> 
> But I am not sure if this solution will introduce new problems.

So, I don't see why bdi->dev should be freed before bdi itself does.
Would something like the following work?

bdi_unregister()
{
        ...
        if (bdi->dev) {
                ...
                device_get(bdi->dev);   // to be put on release
                device_unregister(bdi->dev);
        }
        ...
}

release_bdi()
{
        ...
        if (bdi->dev) {
                // warn if dev is still registered
                device_put(bdi->dev);
        }
        ...
}

Thanks.

-- 
tejun

  reply	other threads:[~2020-02-12 21:33 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-11 14:00 [PATCH] bdi: fix use-after-free for bdi device Yufen Yu
2020-02-11 13:57 ` Yufen Yu
2020-02-12 21:33   ` Tejun Heo [this message]
2020-02-13  2:46     ` Yufen Yu
2020-02-13  3:48       ` Tejun Heo
2020-02-13  7:51         ` Yufen Yu
2020-02-13 13:58           ` Tejun Heo
2020-02-14  2:50             ` Yufen Yu
2020-02-14 14:05               ` Tejun Heo
2020-02-15 13:54                 ` Yufen Yu
2020-02-19 12:55                   ` Jan Kara
2020-02-19 15:12                     ` Tejun Heo
2020-02-20 11:07                     ` Yufen Yu
2020-02-20 12:07                       ` Jan Kara

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