From: linux@armlinux•org.uk (Russell King - ARM Linux)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH] bus: vexpress-config: fix device reference leak
Date: Fri, 4 Nov 2016 12:21:07 +0000 [thread overview]
Message-ID: <20161104122107.GA1041@n2100.armlinux.org.uk> (raw)
In-Reply-To: <1478259746.17152.126.camel@arm.com>
On Fri, Nov 04, 2016 at 11:42:26AM +0000, Pawel Moll wrote:
> On Tue, 2016-11-01 at 11:43 +0100, Johan Hovold wrote:
> > Make sure to drop the reference to the parent device taken by
> > class_find_device() after populating the bus.
> >
> > Fixes: 3b9334ac835b ("mfd: vexpress: Convert custom func API to
> > regmap")
> > Signed-off-by: Johan Hovold <johan@kernel•org>
>
> You're right. May I ask how did you figure it out? The get_device()
> happening in class_find_device() is a bit obscure,
It's not obscure at all - all the functions that find a device do so
under a lock to ensure that the device does not go away, and they
take a reference count on the device before returning the pointer for
exactly the same reason.
If they didn't do that, the find function could locate a struct device
while another thread is deleting the struct device, and it would then
return a stale pointer - and dereferencing that pointer would then be
a use-after-free bug.
So not obscure, but rather fundamentally necessary.
--
RMK's Patch system: http://www.armlinux.org.uk/developer/patches/
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next prev parent reply other threads:[~2016-11-04 12:21 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-11-01 10:43 [PATCH] bus: vexpress-config: fix device reference leak Johan Hovold
2016-11-04 11:42 ` Pawel Moll
2016-11-04 12:21 ` Russell King - ARM Linux [this message]
2016-11-04 13:03 ` Johan Hovold
2016-11-16 16:48 ` Sudeep Holla
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