linux-kernel - Re: [PATCH] input: synaptics_i2c - cancel delayed work before freeing device

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Message-ID: <py7u3qpp6s4nfdceefufkjpbyhkj7wp2kyetlw54vlhdp4gmwn@6vghr6bqkbxc>
Date: Fri, 12 Dec 2025 20:38:23 -0800
From: Dmitry Torokhov <dmitry.torokhov@...il.com>
To: Mike Rapoport <rppt@...nel.org>, Marek Vasut <marek.vasut@...lbox.org>
Cc: Minseong Kim <ii4gsp@...il.com>, linux-input@...r.kernel.org, 
	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH] input: synaptics_i2c - cancel delayed work before
 freeing device

On Wed, Dec 10, 2025 at 09:25:38PM +0900, Mike Rapoport wrote:
> Hi,
> 
> On Tue, Dec 09, 2025 at 08:40:54PM -0800, Dmitry Torokhov wrote:
> > Hi Minseong,
> > 
> > On Wed, Dec 10, 2025 at 12:20:27PM +0900, Minseong Kim wrote:
> > > synaptics_i2c_irq() schedules touch->dwork via mod_delayed_work().
> > > The delayed work performs I2C transactions and may still be running
> > > (or get queued) when the device is removed.
> > > 
> > > synaptics_i2c_remove() currently frees 'touch' without canceling
> > > touch->dwork. If removal happens while the work is pending/running,
> > > the work handler may dereference freed memory, leading to a potential
> > > use-after-free.
> > > 
> > > Cancel the delayed work synchronously before unregistering/freeing
> > > the device.
> > > 
> > > Fixes: eef3e4cab72e Input: add driver for Synaptics I2C touchpad
> > > Reported-by: Minseong Kim <ii4gsp@...il.com>
> > > Cc: stable@...r.kernel.org
> > > Signed-off-by: Minseong Kim <ii4gsp@...il.com>
> > > ---
> > >  drivers/input/mouse/synaptics_i2c.c | 2 ++
> > >  1 file changed, 2 insertions(+)
> > > 
> > > diff --git a/drivers/input/mouse/synaptics_i2c.c b/drivers/input/mouse/synaptics_i2c.c
> > > index a0d707e47d93..fe30bf9aea3a 100644
> > > --- a/drivers/input/mouse/synaptics_i2c.c
> > > +++ b/drivers/input/mouse/synaptics_i2c.c
> > > @@ -593,6 +593,8 @@ static void synaptics_i2c_remove(struct i2c_client *client)
> > >  	if (!polling_req)
> > >  		free_irq(client->irq, touch);
> > >  
> > > +	cancel_delayed_work_sync(&touch->dwork);
> > > +
> > 
> > The call to cancel_delayed_work_sync() happens in the close() handler
> > for the device. I see that in resume we restart the polling without
> > checking if the device is opened, so if we want to fix it we should add
> > the checks there.
> > 
> > However support for the PXA board using in the device with this touch
> > controller (eXeda) was removed a while ago. Mike, you're one of the
> > authors, any objections to simply removing the driver? 
>  
> No objections from my side.

Hmm, it looks like it is still referenced from
arch/arm/boot/dts/nxp/mxs/imx23-sansa.dts

Marek, is this device still relevant?

Thanks.

-- 
Dmitry