linux-kernel - Re: [PATCH] HID: hid-input: Fix accessing freed memory during driver unbind

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Message-ID: <20150729174619.GC23178@dtor-ws>
Date:	Wed, 29 Jul 2015 10:46:19 -0700
From:	Dmitry Torokhov <dmitry.torokhov@...il.com>
To:	Jiri Kosina <jkosina@...e.com>
Cc:	Krzysztof Kozlowski <k.kozlowski@...sung.com>,
	linux-input@...r.kernel.org, linux-kernel@...r.kernel.org,
	sre@...nel.org, linux-pm@...r.kernel.org,
	"H.J. Lu" <hjl.tools@...il.com>, stable@...r.kernel.org
Subject: Re: [PATCH] HID: hid-input: Fix accessing freed memory during driver
 unbind

On Wed, Jul 29, 2015 at 03:07:04PM +0200, Jiri Kosina wrote:
> On Tue, 28 Jul 2015, Krzysztof Kozlowski wrote:
> 
> > During unbinding the driver was dereferencing a pointer to memory
> > already freed by power_supply_unregister().
> > 
> > Driver was freeing its internal description of battery through pointers
> > stored in power_supply structure. However, because the core owns the
> > power supply instance, after calling power_supply_unregister() the
> > driver cannot access these members.
> > 
> > Fix this by using resource-managed allocations so internal data will be
> > freed by pointers stored in resource-managed core.
> > 
> > Signed-off-by: Krzysztof Kozlowski <k.kozlowski@...sung.com>
> > Reported-by: H.J. Lu <hjl.tools@...il.com>
> > Fixes: 297d716f6260 ("power_supply: Change ownership from driver to core")
> > Cc: <stable@...r.kernel.org>
> 
> Applied to for-4.2/upstream-fixes, thanks.

Wait, what guarantees do we have that this is only called in probe()
paths? Don't we allow hid_hw_start() be deferred to open() calls?

In general we need to be careful with devm* conversions in core code.

Thanks.

-- 
Dmitry
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