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Date: Thu, 18 Feb 2016 15:46:07 -0800 From: Greg KH <gregkh@...uxfoundation.org> To: Paul Bolle <pebolle@...cali.nl> Cc: netdev@...r.kernel.org, Dmitry Vyukov <dvyukov@...gle.com>, Uwe Kleine-König <u.kleine-koenig@...gutronix.de>, Martin Wilck <Martin.Wilck@...fujitsu.com>, Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>, Tilman Schmidt <tilman@...p.cc>, linux-kernel@...r.kernel.org, gigaset307x-common@...ts.sourceforge.net Subject: Re: [PATCH 1/1] ser_gigaset: use container_of() instead of detour On Thu, Feb 18, 2016 at 09:29:08PM +0100, Paul Bolle wrote: > The purpose of gigaset_device_release() is to kfree() the struct > ser_cardstate that contains our struct device. This is done via a bit of > a detour. First we make our struct device's driver_data point to the > container of our struct ser_cardstate (which is a struct cardstate). In > gigaset_device_release() we then retrieve that driver_data again. And > after that we finally kfree() the struct ser_cardstate that was saved in > the struct cardstate. > > All of this can be achieved much easier by using container_of() to get > from our struct device to its container, struct ser_cardstate. Do so. > > Note that at the time the detour was implemented commit b8b2c7d845d5 > ("base/platform: assert that dev_pm_domain callbacks are called > unconditionally") had just entered the tree. That commit disconnected > our platform_device and our platform_driver. These were reconnected > again in v4.5-rc2 through commit 25cad69f21f5 ("base/platform: Fix > platform drivers with no probe callback"). And one of the consequences > of that fix was that it broke the detour via driver_data. That's because > it made __device_release_driver() stop being a NOP for our struct device > and actually do stuff again. One of the things it now does, is setting > our driver_data to NULL. That, in turn, makes it impossible for > gigaset_device_release() to get to our struct cardstate. Which has the > net effect of leaking a struct ser_cardstate at every call of this > driver's tty close() operation. So using container_of() has the > additional benefit of actually working. > > Reported-by: Dmitry Vyukov <dvyukov@...gle.com> > Tested-by: Dmitry Vyukov <dvyukov@...gle.com> > Signed-off-by: Paul Bolle <pebolle@...cali.nl> > --- > drivers/isdn/gigaset/ser-gigaset.c | 9 +-------- > 1 file changed, 1 insertion(+), 8 deletions(-) <formletter> This is not the correct way to submit patches for inclusion in the stable kernel tree. Please read Documentation/stable_kernel_rules.txt for how to do this properly. </formletter>
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