Re: [PATCH] intel_menlow: set cdev after null device check to avoid null pointer dereference

From	Darren Hart <dvhart@infradead.org>
Newsgroups	linux.kernel
Subject	Re: [PATCH] intel_menlow: set cdev after null device check to avoid null pointer dereference
Date	2016-04-10 04:40 +0200
Message-ID	<rmds6-6AZ-5@gated-at.bofh.it> (permalink)
References	<rhI3v-13T-3@gated-at.bofh.it> <rhK5k-2r4-13@gated-at.bofh.it> <ri1IV-6LW-65@gated-at.bofh.it>
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On Tue, Mar 29, 2016 at 03:13:43PM +0200, Rafael Wysocki wrote:
> On Monday, March 28, 2016 11:18:05 AM Darren Hart wrote:
> > On Mon, Mar 28, 2016 at 05:18:39PM +0100, Colin King wrote:
> > > From: Colin Ian King <colin.king@canonical.com>
> > > 
> > > intel_menlow_memory_remove sanity checks to see if device is null, however,
> > > this check is performed after we have already passed device into a call
> > > to acpi_driver_data.  If device is null, then acpi_driver_data will produce
> > > a null pointer dereference on device. The correct action is to sanity check
> > > device, then assign cdev, then check if cdev is null.
> > > 
> > 
> > Hrm, looking at this locally, that all makes sense.
> > 
> > Taking a step back however, I notice that intel_menlow_memory_remove is an ops
> > function pointer inside the acpi_driver structure itself, which is called from
> > acpi_device_remove() (and probe) (drivers/acpi/bus.c). This already verifies
> > acpi_driver is not NULL and can't get acpi_driver if acpi_device is NULL. So
> > unless there is some other use case for this callback I'm unaware of (certainly
> > possible) it appears to be totally redundant to do this checking here.
> > 
> > +Rafael - is there a best practices for these acpi callbacks with respect to
> > input validation?
> 
> No best practices I'm aware of, but if the core does this checks anyway before
> calling this, they are clearly not necessary here.

My position as well.

Colin, would you care to respin these 2?

-- 
Darren Hart
Intel Open Source Technology Center

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Re: [PATCH] intel_menlow: set cdev after null device check to avoid  null pointer dereference Darren Hart <dvhart@infradead.org> - 2016-04-10 04:40 +0200

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