linux-kernel - Re: [PATCH v2] Input: usbtouchscreen

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Message-ID: <YrorjZDRXMgITIjZ@google.com>
Date:   Mon, 27 Jun 2022 15:13:33 -0700
From:   Dmitry Torokhov <dmitry.torokhov@...il.com>
To:     Johan Hovold <johan@...nel.org>
Cc:     linux-input@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] Input: usbtouchscreen - add driver_info sanity check

On Mon, Jun 27, 2022 at 09:46:27AM +0200, Johan Hovold wrote:
> On Thu, Jun 23, 2022 at 08:59:52AM -0700, Dmitry Torokhov wrote:
> > On Thu, Jun 23, 2022 at 08:24:46AM +0200, Johan Hovold wrote:
> > > Add a sanity check on the device id-table driver_info field to make sure
> > > we never access a type structure (and function pointers) outside of the
> > > device info array (e.g. if someone fails to ifdef a device-id entry).
> > > 
> > > Note that this also suppresses a compiler warning with -Warray-bounds
> > > (gcc-11.3.0) when compile-testing the driver without enabling any of
> > > the device type Kconfig options:
> > > 
> > >     drivers/input/touchscreen/usbtouchscreen.c: In function 'usbtouch_probe':
> > >     drivers/input/touchscreen/usbtouchscreen.c:1668:16:warning: array subscript <unknown> is outside array bounds of 'struct usbtouch_device_info[0]' [-Warray-bounds]
> > >      1668 |         type = &usbtouch_dev_info[id->driver_info];
> > > 
> > > Signed-off-by: Johan Hovold <johan@...nel.org>
> > > ---
> > > 
> > > Changes in v2
> > >  - use ARRAY_SIZE() for the sanity check (Dmitry)
> > >  - drop the dummy entry and combine the two patches as the sanity check
> > >    itself is enough to suppress the compiler warning (Dmitry)
> > >  - use -ENODEV instead of -EINVAL even if this means no error will be
> > >    logged in the unlikely event of a future driver bug
> > 
> > Is this on purpose or because I happened to have used this error code
> > when I suggested the change? I'm fine with returning -EINVAL there.
> 
> It was on purpose. Returning -EINVAL (invalid argument) here just
> doesn't seem quite right. I skimmed the errno list for a better
> alternative, but decided -ENODEV works as well.
> 
> If there's ever a driver bug that triggers this, you could say the
> device isn't supported in that configuration. ;)
> 
> If you prefer -EINVAL, I'll change it back.

No, that is fine, I was simply making sure. Applied, thank you.

-- 
Dmitry