Re: [PATCH] Input: synaptics-rmi4 - Avoid processing unknown IRQs

From: Dmitry Torokhov
Date: Thu Oct 17 2019 - 14:04:09 EST


On Fri, Oct 11, 2019 at 09:46:56PM +0000, Andrew Duggan wrote:
> Hi Evan,
>
> On 10/8/19 3:36 PM, Evan Green wrote:
> > rmi_process_interrupt_requests() calls handle_nested_irq() for
> > each interrupt status bit it finds. If the irq domain mapping for
> > this bit had not yet been set up, then it ends up calling
> > handle_nested_irq(0), which causes a NULL pointer dereference.
> >
> > There's already code that masks the irq_status bits coming out of the
> > hardware with current_irq_mask, presumably to avoid this situation.
> > However current_irq_mask seems to more reflect the actual mask set
> > in the hardware rather than the IRQs software has set up and registered
> > for. For example, in rmi_driver_reset_handler(), the current_irq_mask
> > is initialized based on what is read from the hardware. If the reset
> > value of this mask enables IRQs that Linux has not set up yet, then
> > we end up in this situation.
> >
> > There appears to be a third unused bitmask that used to serve this
> > purpose, fn_irq_bits. Use that bitmask instead of current_irq_mask
> > to avoid calling handle_nested_irq() on IRQs that have not yet been
> > set up.
>
> Yes, it looks like the code which ensured that there was a function
> handler to handle the IRQ was removed when the driver switched to using
> an irq domain. Setting the fn_irq_bits and using them instead of
> current_irq_mask in rmi_process_interrupt_requests() makes sense to me.
>
> Andrew
>
> > Signed-off-by: Evan Green <evgreen@xxxxxxxxxxxx>
> Reviewed-by: Andrew Duggan <aduggan@xxxxxxxxxxxxx>

Applied, thank you.

> > ---
> >
> > drivers/input/rmi4/rmi_driver.c | 6 +++++-
> > 1 file changed, 5 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/input/rmi4/rmi_driver.c b/drivers/input/rmi4/rmi_driver.c
> > index 772493b1f665..190b9974526b 100644
> > --- a/drivers/input/rmi4/rmi_driver.c
> > +++ b/drivers/input/rmi4/rmi_driver.c
> > @@ -146,7 +146,7 @@ static int rmi_process_interrupt_requests(struct rmi_device *rmi_dev)
> > }
> >
> > mutex_lock(&data->irq_mutex);
> > - bitmap_and(data->irq_status, data->irq_status, data->current_irq_mask,
> > + bitmap_and(data->irq_status, data->irq_status, data->fn_irq_bits,
> > data->irq_count);
> > /*
> > * At this point, irq_status has all bits that are set in the
> > @@ -385,6 +385,8 @@ static int rmi_driver_set_irq_bits(struct rmi_device *rmi_dev,
> > bitmap_copy(data->current_irq_mask, data->new_irq_mask,
> > data->num_of_irq_regs);
> >
> > + bitmap_or(data->fn_irq_bits, data->fn_irq_bits, mask, data->irq_count);
> > +
> > error_unlock:
> > mutex_unlock(&data->irq_mutex);
> > return error;
> > @@ -398,6 +400,8 @@ static int rmi_driver_clear_irq_bits(struct rmi_device *rmi_dev,
> > struct device *dev = &rmi_dev->dev;
> >
> > mutex_lock(&data->irq_mutex);
> > + bitmap_andnot(data->fn_irq_bits,
> > + data->fn_irq_bits, mask, data->irq_count);
> > bitmap_andnot(data->new_irq_mask,
> > data->current_irq_mask, mask, data->irq_count);
> >

--
Dmitry