[PATCH] Input: elan_i2c - prevent division by zero on invalid device parameters

[PATCH] Input: elan_i2c - prevent division by zero on invalid device parameters

[Ranjan Kumar]

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, y_traces, x_mm, or y_mm, it results in a fatal
division-by-zero exception leading to a kernel panic during device probe.

Add sanity checks to ensure these physical parameters are non-zero
before performing the division. If invalid values are detected, log an
error and return -EINVAL to gracefully abort the initialization and
maintain system stability.

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>
---
 drivers/input/mouse/elan_i2c_core.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/drivers/input/mouse/elan_i2c_core.c b/drivers/input/mouse/elan_i2c_core.c
index fee1796da3d0..b5fd63928afd 100644
--- a/drivers/input/mouse/elan_i2c_core.c
+++ b/drivers/input/mouse/elan_i2c_core.c
@@ -425,6 +425,14 @@ static int elan_query_device_parameters(struct elan_tp_data *data)
 		if (error)
 			return error;
 	}
+
+	if (unlikely(x_traces == 0 || y_traces == 0)) {
+		dev_err(&client->dev,
+			"Invalid trace numbers: x=%u, y=%u\n",
+			x_traces, y_traces);
+		return -EINVAL;
+	}
+
 	data->width_x = data->max_x / x_traces;
 	data->width_y = data->max_y / y_traces;
 
@@ -440,6 +448,14 @@ static int elan_query_device_parameters(struct elan_tp_data *data)
 		data->x_res = elan_convert_resolution(hw_x_res, data->pattern);
 		data->y_res = elan_convert_resolution(hw_y_res, data->pattern);
 	} else {
+
+		if (unlikely(x_mm == 0 || y_mm == 0)) {
+			dev_err(&client->dev,
+				"Invalid physical dimensions: x_mm=%u, y_mm=%u\n",
+				x_mm, y_mm);
+			return -EINVAL;
+		}
+
 		data->x_res = (data->max_x + 1) / x_mm;
 		data->y_res = (data->max_y + 1) / y_mm;
 	}
-- 
2.54.0.563.g4f69b47b94-goog

Re: [PATCH] Input: elan_i2c - prevent division by zero on invalid device parameters

[Dmitry Torokhov]

Hi Ranjan,

On Wed, May 13, 2026 at 07:39:08AM +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, y_traces, x_mm, or y_mm, it results in a fatal
> division-by-zero exception leading to a kernel panic during device probe.
> 

Neither crashing nor aborting probe with -EINVAL is great as we will not
be able to flash another firmware.

How do we get into this state? Is this something actually observed or
just theoretical?

> Add sanity checks to ensure these physical parameters are non-zero
> before performing the division. If invalid values are detected, log an
> error and return -EINVAL to gracefully abort the initialization and
> maintain system stability.

That is hardly "stability" for a laptop when its pointer is not working.

Thanks.

-- 
Dmitry