linux-kernel - Re: [PATCH] iio: accel: fxls8962af: Fix use after free in fxls8962af_fifo

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Message-ID: <aDnwMDGDf3-KUb3J@smile.fi.intel.com>
Date: Fri, 30 May 2025 20:51:44 +0300
From: Andy Shevchenko <andy.shevchenko@...il.com>
To: David Lechner <dlechner@...libre.com>
Cc: Sean Nyekjaer <sean@...nix.com>, Jonathan Cameron <jic23@...nel.org>,
	Nuno Sá <nuno.sa@...log.com>,
	Jonathan Cameron <Jonathan.Cameron@...wei.com>,
	linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Subject: Re: [PATCH] iio: accel: fxls8962af: Fix use after free in
 fxls8962af_fifo_flush

On Thu, May 29, 2025 at 01:49:16PM -0500, David Lechner wrote:
> On 5/29/25 1:16 PM, Andy Shevchenko wrote:
> > On Thu, May 29, 2025 at 7:02 PM David Lechner <dlechner@...libre.com> wrote:
> >> On 5/24/25 5:34 AM, Sean Nyekjaer wrote:

...

> >> fxls8962af_suspend() calls enable_irq_wake(data->irq); before disabling the
> >> interrupt by calling fxls8962af_buffer_predisable(indio_dev);
> >>
> >> It seems like the order should be reversed.
> > 
> > AFAIU the wake capability of IRQ line is orthogonal to the interrupt
> > controller enabling (unmasking) / disabling (masking) the line itself.
> > Or did you mean something else?
> 
> I don't know enough about how suspend/wake stuff works to say for sure.
> 
> I just saw the comment:
> 
> 	/*
> 	 * Disable buffer, as the buffer is so small the device will wake
> 	 * almost immediately.
> 	 */
> 
> so I assumed someone had observed something like this happening already.
> If an interrupt occurs between enable_irq_wake() and actually
> going into a low power mode, what effect does it have? I ask because I
> don't know.

To be a "wake source" means to be capable of signaling to the system that wake
is needed. If an event comes after enabling an IRQ line to be a wake source,
that should wakeup the system (independently if that IRQ line is disabled or
not on the IRQ controller side).

-- 
With Best Regards,
Andy Shevchenko