From: Dmitry Torokhov <dmitry.torokhov@gmail.com>
To: Jacek Anaszewski <jacek.anaszewski@gmail.com>
Cc: Sven Van Asbroeck <thesven73@gmail.com>,
Tejun Heo <tj@kernel.org>, Lai Jiangshan <jiangshanlai@gmail.com>,
linux-kernel@vger.kernel.org, Sebastian Reichel <sre@kernel.org>,
Kees Cook <keescook@chromium.org>
Subject: Re: [RFC v1 3/3] cap11xx: fix potential user-after-free on module unload
Date: Tue, 5 Feb 2019 13:43:51 -0800 [thread overview]
Message-ID: <20190205214351.GB19151@dtor-ws> (raw)
In-Reply-To: <6565ec19-b629-c289-2fed-a5f404763b74@gmail.com>
On Tue, Feb 05, 2019 at 10:24:47PM +0100, Jacek Anaszewski wrote:
> Hi Dmitry,
>
> On 2/5/19 9:18 AM, Dmitry Torokhov wrote:
> > Hi Sven,
> >
> > On Mon, Feb 04, 2019 at 05:09:52PM -0500, Sven Van Asbroeck wrote:
> > > The work which is scheduled by led_classdev->brightness_set() is
> > > potentially left pending or running until after the driver module
> > > is unloaded.
> > >
> > > Fix by using resource-controlled version of INIT_WORK().
> >
> > I believe this is wrong way of fixing this. The LED classdev objects are
> > refcounted, and may live beyond the point where we unwibd devm stack,
> > so we are still left with the same use-after-free that we currently
> > have.
>
> Could you please share what LED classdev objects refcounting
> do you have on mind?
My mind was in a state of confusion when I wrote the above ;)
>
> > This is a general issue with LED subsystem as it provides no callback
> > for properly tearing down device structures, but I think in this
> > particular case we can simply switch from set_brightness() to
> > set_brightness_blocking() which will use the work item internal to the
> > LED classdev and that one is being shut down properly.
> >
> > Jacek, does the above sound right?
>
> Yes, since the introduction of brightness_set_blocking op there is no
> need for out-of-led-core workqueues for deferring brightness setting.
> And we do flush_work() in led_classdev_unregister().
OK, great, I'll write up a patch for cap11xx and others if I find them.
Thanks.
--
Dmitry
next prev parent reply other threads:[~2019-02-05 21:44 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-02-04 22:09 [RFC v1 0/3] Address potential user-after-free on module unload Sven Van Asbroeck
2019-02-04 22:09 ` [RFC v1 1/3] workqueue: Add resource-managed version of INIT_[DELAYED_]WORK() Sven Van Asbroeck
2019-02-08 17:06 ` Tejun Heo
2019-02-08 18:15 ` Sven Van Asbroeck
2019-02-04 22:09 ` [RFC v1 2/3] max17042_battery: fix potential user-after-free on module unload Sven Van Asbroeck
2019-02-05 8:27 ` Dmitry Torokhov
2019-02-05 14:27 ` Sven Van Asbroeck
2019-02-05 17:21 ` Sebastian Reichel
2019-02-04 22:09 ` [RFC v1 3/3] cap11xx: " Sven Van Asbroeck
2019-02-05 8:18 ` Dmitry Torokhov
2019-02-05 8:34 ` Dmitry Torokhov
2019-02-05 21:24 ` Jacek Anaszewski
2019-02-05 21:43 ` Dmitry Torokhov [this message]
2019-02-05 22:03 ` Sven Van Asbroeck
2019-02-05 14:57 ` [RFC v1 0/3] Address " Kees Cook
2019-02-05 15:22 ` Sven Van Asbroeck
2019-02-05 18:43 ` Greg KH
2019-02-05 19:12 ` Sven Van Asbroeck
2019-02-06 16:46 ` Greg KH
2019-02-06 17:30 ` Dmitry Torokhov
2019-02-06 17:49 ` Sven Van Asbroeck
2019-02-08 6:51 ` Greg KH
2019-02-05 18:42 ` Greg KH
2019-02-07 21:49 ` Sven Van Asbroeck
2019-02-07 22:20 ` Dmitry Torokhov
2019-02-07 22:27 ` Sven Van Asbroeck
2019-02-07 22:32 ` Sven Van Asbroeck
2019-02-07 22:48 ` Dmitry Torokhov
2019-02-08 4:30 ` Miguel Ojeda
2019-02-10 18:05 ` Sven Van Asbroeck
2019-02-14 1:11 ` Miguel Ojeda
2019-02-14 15:23 ` Sven Van Asbroeck
[not found] ` <CAGngYiXcogd69n-MvBD1n5ZJpBzqCau8UOfLMgXEXLnAev=srw@mail.gmail.com>
[not found] ` <alpine.DEB.2.21.1902080745480.4201@hadrien>
2019-02-14 17:52 ` Fwd: " Sven Van Asbroeck
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