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: Fri, 14 Feb 2020 09:05:14 -0500 [thread overview]
Message-ID: <20200214140514.GL88887@mtj.thefacebook.com> (raw)
In-Reply-To: <f369a99d-e794-0c1b-85cf-83b577fb0f46@huawei.com>
Hello,
On Fri, Feb 14, 2020 at 10:50:01AM +0800, Yufen Yu wrote:
> > So, unregistering can leave ->dev along and re-registering can test
> > whether it's NULL and if not put the existing one and put a new one
> > there. Wouldn't that work?
>
> Do you mean set bdi->dev as 'NULL' in call_rcu() callback function
> (i.e. bdi_release_device()) and test 'bdi->dev' in bdi_register_va()?
>
> I think that may do not work.
> We cannot make sure the order of rcu callback function and re-registering.
> Then bdi_release_device() may put the new allocated device by re-registering.
No, I meant not freeing bdi->dev on deregistration and only doing so
when it actually needs to - on re-registration or release. So, sth
like the following.
* Unregister: Unregister bdi->dev but don't free it. Leave the pointer
alone.
* Re-register: If bdi->dev is not null, initiate RCU-free and update
bdi->dev to the new dev.
* Release: If bdi->dev is not NULL, initiate RCU-free of it.
Thanks.
--
tejun
next prev parent reply other threads:[~2020-02-14 14:05 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
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 [this message]
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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