Re: [PATCH] Input: synaptics-rmi4 - fix use after free (more completely) -- but not fully ;)

[Dmitry Torokhov <dmitry.torokhov@gmail.com>]

On Thu, Feb 22, 2024 at 03:19:49PM +0100, Mathias Krause wrote:
> On 22.02.24 15:08, Mathias Krause wrote:
> >>
> >> The bug is that we must not call device_del() until after calling
> >> irq_dispose_mapping().
> > 
> > Unfortunately, this is only half the truth. We investigated this further
> > and there's another bug that got introduced in commit 24d28e4f1271
> > ("Input: synaptics-rmi4 - convert irq distribution to irq_domain"). The
> > IRQ domain has a UAF issue as well. I'll send the patch soon -- wanted
> > to do so this week, but, again, more urgent matters interrupted this.
> 
> Unfortunately, I send that Email too fast. Looking at the backtrace
> again, it's just the other bug that needs fixing (a UAF in
> rmi_driver_remove()). Will sent a patch really soon now!
> 
> > 
> >>
> >> Fixes: 24d28e4f1271 ("Input: synaptics-rmi4 - convert irq distribution to irq_domain")
> >> Reported-by: Torsten Hilbrich <torsten.hilbrich@secunet.com>
> >> Closes: https://lore.kernel.org/all/1932038e-2776-04ac-5fcd-b15bb3cd088d@secunet.com/
> >> Closes: https://bugzilla.kernel.org/show_bug.cgi?id=215604
> >> Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
> >> ---
> >>  drivers/input/rmi4/rmi_bus.c | 5 ++---
> >>  1 file changed, 2 insertions(+), 3 deletions(-)
> >>
> >> diff --git a/drivers/input/rmi4/rmi_bus.c b/drivers/input/rmi4/rmi_bus.c
> >> index 1b45b1d3077d..02acc81b9d3e 100644
> >> --- a/drivers/input/rmi4/rmi_bus.c
> >> +++ b/drivers/input/rmi4/rmi_bus.c
> >> @@ -275,12 +275,11 @@ void rmi_unregister_function(struct rmi_function *fn)
> >>  	rmi_dbg(RMI_DEBUG_CORE, &fn->dev, "Unregistering F%02X.\n",
> >>  			fn->fd.function_number);
> >>  
> >> -	device_del(&fn->dev);
> >> -	of_node_put(fn->dev.of_node);
> >> -
> >>  	for (i = 0; i < fn->num_of_irqs; i++)
> >>  		irq_dispose_mapping(fn->irq[i]);
> >>  
> >> +	device_del(&fn->dev);
> >> +	of_node_put(fn->dev.of_node);
> >>  	put_device(&fn->dev);
> >>  }
> >>  
> > 
> > Acked-by: Mathias Krause <minipli@grsecurity.net>
> 
> So, forget about that one, sorry.

Right, I do not think this patch is needed. The "fn" will stay in memory
until the last reference to fn->dev is dropped. So the original patch
was enough for this particular issue, and Mathias' patch fixes slightly
different UAF.

Thanks.

-- 
Dmitry