Re: [PATCH v4] Input: elan_i2c - prevent division by zero and arithmetic underflow

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

On Fri, Jun 12, 2026 at 06:03:39AM +0000, Ranjan Kumar wrote:
> The Elan I2C touchpad driver queries the device for its physical
> dimensions and trace counts to calculate the device resolution and width.
> However, if the device firmware or device tree provides invalid zero
> values for x_traces or y_traces, it results in a fatal division-by-zero
> exception leading to a kernel panic during device probe.
> 
> Add checks to ensure these parameters are non-zero before performing
> the division. If invalid trace values are detected, fall back to a safe
> default of 1.
> 
> Additionally, prevent an arithmetic underflow in the touch reporting
> logic. Previously, if the calculated or fallback width was smaller than
> ETP_FWIDTH_REDUCE (90), the subtraction would underflow, resulting in a
> massive unsigned integer being reported to userspace. Clamp the adjusted
> width to a minimum of 0 to safely handle small physical dimensions and
> fallback scenarios.
> 
> Completing the probe with safe fallback values ensures the sysfs nodes
> are created, keeping the firmware update path intact so a recovery
> firmware can be flashed to the device.
> 
> Fixes: 6696777c6506 ("Input: add driver for Elan I2C/SMbus touchpad")
> Fixes: e3a9a1290688 ("Input: elan_i2c - do not query the info if they are provided")
> Signed-off-by: Ranjan Kumar <kumarranja@chromium.org>

Applied, thank you.

-- 
Dmitry