Re: [PATCH] iio: chemical: atlas-sensor: use iio_trigger_poll_nested() to fix remove UAF

[Jonathan Cameron <jic23@kernel.org>]

On Mon, 03 Aug 2026 02:24:38 +0000
Matt Ranostay <matt@ranostay.sg> wrote:

> On Monday, 3 August 2026 at 02:32, Jonathan Cameron <jic23@kernel.org> wrote:
> 
> > On Sun,  2 Aug 2026 07:18:58 +0000
> > Fan Wu <fanwu01@zju.edu.cn> wrote:
> >   
> > > The atlas driver requests its hardware data-ready IRQ with
> > > devm_request_threaded_irq(); its threaded handler queues an irq_work,
> > > atlas_work_handler(), that calls iio_trigger_poll(data->trig).
> > >
> > > The IRQ is devm-managed, so free_irq() runs from the devres unwind after
> > > atlas_remove() returns without flushing that irq_work.  Once a buffer is
> > > enabled, conversion-complete IRQs keep firing and queueing it; a pending
> > > irq_work can therefore run after the unwind has freed atlas_data/indio_dev
> > > and the trigger, when atlas_work_handler() derives the atlas_data pointer
> > > via container_of() and dereferences data->trig, a use-after-free.
> > >
> > > Call iio_trigger_poll_nested() directly from the threaded handler instead
> > > of bouncing through irq_work.  free_irq() then drains the threaded handler,
> > > closing the window; other iio drivers with a threaded data-ready IRQ do the
> > > same (e.g. bmi270).
> > >
> > > This issue was found by an in-house static analysis tool.
> > >
> > > Fixes: 7103b99b031c ("iio: chemical: atlas-ph-sensor: reorg driver to allow multiple chips")
> > > Cc: stable@vger.kernel.org # v6.4+
> > > Assisted-by: Codex:gpt-5.6
> > > Signed-off-by: Fan Wu <fanwu01@zju.edu.cn>  
> > 
> > Added another email address for Matt.
> > 
> > There are reasons why he might have got the irq_work route but I can't
> > recall if they applied.  What we lose here is the ability to hang
> > other consumers that need a top half of the trigger.  If that doesn't
> > matter then agreed your solution is the cleanest path forwards.  
> 
> Hello all! Looking at the 'git log' and 10 years ago so it I'm only doing conjecture on what I was probably thinking back in 2016.
> If I recall the reasoning was to allow other consumer iio triggers (e.g. hrtimer timer or sysfs)
> to map to the atlas sensors.
> 

That way around shouldn't require this.  Using this to trigger
others would.  Meh, long time back as you note!

Anyhow, let's rip it out and see if anyone screams :)

Applied to the fixes-togreg branch of iio.git.

Jonathan


> Thanks,
> 
> Matt
> 
> > 
> > One day someone will get the time to make combining nested
> > trigger handling with top halves cleverer than current approach of
> > just not running them.
> > 
> > Jonathan
> > 
> >   
> > > ---
> > >
> > >  drivers/iio/chemical/atlas-sensor.c | 13 +------------
> > >  1 file changed, 1 insertion(+), 12 deletions(-)
> > >
> > > diff --git a/drivers/iio/chemical/atlas-sensor.c b/drivers/iio/chemical/atlas-sensor.c
> > > --- a/drivers/iio/chemical/atlas-sensor.c
> > > +++ b/drivers/iio/chemical/atlas-sensor.c
> > > @@ -13,7 +13,6 @@
> > >  #include <linux/mutex.h>
> > >  #include <linux/err.h>
> > >  #include <linux/irq.h>
> > > -#include <linux/irq_work.h>
> > >  #include <linux/i2c.h>
> > >  #include <linux/mod_devicetable.h>
> > >  #include <linux/regmap.h>
> > > @@ -88,7 +87,6 @@ struct atlas_data {
> > >  	struct iio_trigger *trig;
> > >  	const struct atlas_device *chip;
> > >  	struct regmap *regmap;
> > > -	struct irq_work work;
> > >  	unsigned int interrupt_enabled;
> > >  	/* 96-bit data + 32-bit pad + 64-bit timestamp */
> > >  	__be32 buffer[6] __aligned(8);
> > > @@ -437,13 +435,6 @@ static const struct iio_buffer_setup_ops atlas_buffer_setup_ops = {
> > >  	.predisable = atlas_buffer_predisable,
> > >  };
> > >
> > > -static void atlas_work_handler(struct irq_work *work)
> > > -{
> > > -	struct atlas_data *data = container_of(work, struct atlas_data, work);
> > > -
> > > -	iio_trigger_poll(data->trig);
> > > -}
> > > -
> > >  static irqreturn_t atlas_trigger_handler(int irq, void *private)
> > >  {
> > >  	struct iio_poll_func *pf = private;
> > > @@ -470,7 +461,7 @@ static irqreturn_t atlas_interrupt_handler(int irq, void *private)
> > >  	struct iio_dev *indio_dev = private;
> > >  	struct atlas_data *data = iio_priv(indio_dev);
> > >
> > > -	irq_work_queue(&data->work);
> > > +	iio_trigger_poll_nested(data->trig);
> > >
> > >  	return IRQ_HANDLED;
> > >  }
> > > @@ -666,8 +657,6 @@ static int atlas_probe(struct i2c_client *client)
> > >  		goto unregister_trigger;
> > >  	}
> > >
> > > -	init_irq_work(&data->work, atlas_work_handler);
> > > -
> > >  	if (client->irq > 0) {
> > >  		/* interrupt pin toggles on new conversion */
> > >  		ret = devm_request_threaded_irq(&client->dev, client->irq,
> > > --
> > > 2.43.0
> > >
> > >  
> > 
> >