linux-kernel - RE: [PATCH] devres: Freeing the drs after all release() are called

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Date:	Thu, 7 Nov 2013 00:36:56 +0000
From:	"Liu, Chuansheng" <chuansheng.liu@...el.com>
To:	"tj@...nel.org" <tj@...nel.org>
CC:	Greg KH <gregkh@...uxfoundation.org>,
	"dmitry.torokhov@...il.com" <dmitry.torokhov@...il.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH] devres: Freeing the drs after all release() are called



> -----Original Message-----
> From: Tejun Heo [mailto:htejun@...il.com] On Behalf Of tj@...nel.org
> Sent: Thursday, November 07, 2013 8:30 AM
> To: Liu, Chuansheng
> Cc: Greg KH; dmitry.torokhov@...il.com; linux-kernel@...r.kernel.org
> Subject: Re: [PATCH] devres: Freeing the drs after all release() are called
> 
> Hello, Liu.
> 
> On Thu, Nov 07, 2013 at 12:27:56AM +0000, Liu, Chuansheng wrote:
> > The driver code is as below:
> > _INIT() {
> >
> > A = devm_kzalloc();
> > B= devm_request_threaded_irq(isr_handler);
> > C = devm_kzalloc();
> > }
> >
> > When driver _EXIT, the devres_release_all () will be called.
> > The C will be kfreed before B, but when freeing irq B, the pending isr_handler()
> possibly
> > will access the memory B which has been freed.
> > Then the memory corruption occurred.
> >
> > This patch can solve this scenario.
> 
> Isn't the bug there IRQ being requested before all its resources are
> allocated?  The proposed change just masks the underlying issue or
> incorrectly ordered operations.
Yes, I knew I can put the code always like below:
A = devm_kzalloc();
C = devm_kzalloc();
...
B= devm_request_threaded_irq(isr_handler);

But, the above is just one simple coding prototype, if there are many calling:
E -- > F -- > D -- >... then to devm_kzalloc().

To be honest, it will make code too hard to always adapt the rule?
And I trying to find out every potential devm_kzalloc() before irq requesting.
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