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From: Tejun Heo <tj@kernel.org>
To: Greg KH <gregkh@linuxfoundation.org>
Cc: Yufen Yu <yuyufen@huawei.com>,
	axboe@kernel.dk, linux-block@vger.kernel.org,
	linux-fsdevel@vger.kernel.org, jack@suse.cz, bvanassche@acm.org,
	tytso@mit.edu
Subject: Re: [PATCH v2 0/7] bdi: fix use-after-free for bdi device
Date: Wed, 4 Mar 2020 13:57:39 -0500	[thread overview]
Message-ID: <20200304185739.GN189690@mtj.thefacebook.com> (raw)
In-Reply-To: <20200304172907.GA1864710@kroah.com>

Hey, Greg.

On Wed, Mar 04, 2020 at 06:29:07PM +0100, Greg KH wrote:
> How does that happen?  Who has access to a kobject without also having
> the reference count incremented at the same time?  Is this through sysfs
> or somewhere within the kernel itself?

Hopefully, this part was addressed in the other reply.

> The struct device refcount should be all that is needed, don't use RCU
> just to "delay freeing this object until some later time because someone
> else might have a pointer to id".  That's ripe for disaster.

I think it's an idiomatic use of rcu given the circumstances. Whether
the circumstances are reasonable is totally debatable.

Thanks.

-- 
tejun

  reply	other threads:[~2020-03-04 18:57 UTC|newest]

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-26 11:18 [PATCH v2 0/7] bdi: fix use-after-free for bdi device Yufen Yu
2020-02-26 11:18 ` [PATCH v2 1/7] blk-wbt: use bdi_dev_name() to get device name Yufen Yu
2020-02-26 11:18 ` [PATCH v2 2/7] fs/ceph: " Yufen Yu
2020-02-26 11:18 ` [PATCH v2 3/7] bdi: protect device lifetime with RCU Yufen Yu
2020-03-04 17:05   ` Tejun Heo
2020-03-04 17:22     ` Greg Kroah-Hartman
2020-03-04 17:23       ` Greg Kroah-Hartman
2020-03-04 18:50       ` Tejun Heo
2020-03-04 19:10         ` Theodore Y. Ts'o
2020-03-04 19:15           ` Tejun Heo
2020-03-04 20:05         ` Greg Kroah-Hartman
2020-03-05  1:22           ` Tejun Heo
2020-03-06 16:25             ` Greg Kroah-Hartman
2020-03-07  9:13               ` Yufen Yu
2020-02-26 11:18 ` [PATCH v2 4/7] bdi: create a new function bdi_get_dev_name() Yufen Yu
2020-02-26 11:18 ` [PATCH v2 5/7] bfq: fix potential kernel crash when print dev err info Yufen Yu
2020-02-26 11:18 ` [PATCH v2 6/7] memcg: fix crash in wb_workfn when bdi unregister Yufen Yu
2020-02-26 11:18 ` [PATCH v2 7/7] blk-wbt: replace bdi_dev_name() with bdi_get_dev_name() Yufen Yu
2020-03-04 17:29 ` [PATCH v2 0/7] bdi: fix use-after-free for bdi device Greg KH
2020-03-04 18:57   ` Tejun Heo [this message]
2020-03-04 20:07     ` Greg KH
2020-03-04 19:02   ` Theodore Y. Ts'o

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