From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pf1-f176.google.com (mail-pf1-f176.google.com [209.85.210.176]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 318C53AE184 for ; Fri, 12 Jun 2026 06:05:10 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.210.176 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781244319; cv=none; b=btAUHcAecNtlfMYcToPhg3muw1mN9PRHdnIHYuG0q0MyeQH8IeDLJZtOcxGq9m1MteFgScCSMpPKc6oNTX8zLH4mCljYu2RJI6IuldZgR4vvOIZ8JhZf/V82c+69R2vFLMDTiMS3L2wi6QcOiBQAZAGw+j2wNTOOBPaBtQKWEOE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781244319; c=relaxed/simple; bh=RGbsxkupUge19BKTktVT3c2j6x8Gro8DhveJEyZMbKE=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=aefotNsQXz53T0EHbD3b7iMzT0rna/VbJjt2m9rOZoHM454vLOAUrsc2soVaqbgLAW0sVYoztx395dfwML72xF8ZbHNceUgHk2kiytgaIdtPo3FN2H/bbnLcAKnHV3a0GfkblJg7d7khKqYZvhQ4+1HNYUM+AXGmRRA4gEU6yJc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=chromium.org; spf=pass smtp.mailfrom=chromium.org; dkim=pass (1024-bit key) header.d=chromium.org header.i=@chromium.org header.b=CuE0C/+n; arc=none smtp.client-ip=209.85.210.176 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=chromium.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=chromium.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=chromium.org header.i=@chromium.org header.b="CuE0C/+n" Received: by mail-pf1-f176.google.com with SMTP id d2e1a72fcca58-8423b08b293so333613b3a.3 for ; Thu, 11 Jun 2026 23:05:09 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; t=1781244309; x=1781849109; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=gZhVY0AvrduauhTvBrssxSpj3AMAEp/6iK3/KNj+gtk=; b=CuE0C/+nwi8OqN+tUGUujBoRSGDeHTJ6UhhelCWrb2v43Lj2TlEJrmDGWaysaSLiNs i6yFCwt9q10D9V4p6aBtTYSlBO13jimt/HjOP1+GAKgR4mBy79O9wDfb9q62qJQaSxUi M+1D/9PIhzA1nZo51J2GqJBx+4BcMcLfOn35c= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1781244309; x=1781849109; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-gg:x-gm-message-state:from :to:cc:subject:date:message-id:reply-to; bh=gZhVY0AvrduauhTvBrssxSpj3AMAEp/6iK3/KNj+gtk=; b=YjHihMZliNDD2cdx0TIaWpRPYlaWyi5NXZomh0FyJSXUvy/QD36oggM+MErBrDmx85 U2wetGodMTs0EqHQ6rZwxFYmPmFaLQLV5EJpd9M95Wjg2ixtRrmZmDDeVGnUfjw+hvHY woqvvzsTK8KLpqAlB/N7Mc7rxJI/zk3skEq9E8v7Vi6m4Uehozr76H8GRBXOyevQu/0z +yl9nvIIdSEHnorcGVobKr0Fa0urDY8McH+MZfZwwCkC8BO0H56hKTmJqpAcrrN3rxqw g1P1p+cgyb7QnwxeMkQ9phdtqwYC2xvzjp9LIUHri/jky9kyYfNiA9B8UDf7Au94etW0 Kcpw== X-Forwarded-Encrypted: i=1; AFNElJ/269GmNoJWY2wn4wg1Ha0OR3r35Qks4yvaTr3xcnLqO0zMSDDz0V0U3BSCobDga/e1osa7FhRa6iC0JQ==@vger.kernel.org X-Gm-Message-State: AOJu0YxRiNa4xLB8zUD9yeTQH9pMwGIc+CoInXaxaNolBVUyj9xdlnTL ltq5BwvlmLyDLfKPsg14YWFxgiMrDTYlvRbK+3pbc9HkoBsBuDWZy/diSQIiFajbeQ== X-Gm-Gg: Acq92OFTT+JhdZELlmMNhylAttZDyO9Y+YmetDPPYp65ymKVm8yrCRlxzlc+b1b40sI LjqODnY4YQ2krsaDpDb34+VWjcwrOOBMdPYtjnViDP+LnPLEIlUt94mTP4NxJeauCAnjBPqxGqW AFLb90vgqaWZfK6ApWAbq4U1Jzl9sFz9z69TwW2niYAOJuIiqGnlOj6YGJ6a2UEfSaSvW2DVsGD 35MOrDit4j9VmtW8oXKiRVvEyQ63zjmKHn8/s1vYhgWZCdKGsxcDvHSHaaEzy2cbCph09eDFR2n WFE8B758uF1FteaAh2cjyZvuFEHx0U4GLK3uVxV0mYyE5EP6lxc7Iy4QO8+foLtGwXPbuQaLkaW JHvfn2StdMzb8gZEEdtZs5WpOsuNrBAlAXM0AdQsYhrybIvyRElY4iDEDrXhM7LRzX9c8ECloFU zih7ycEgOBUv//5BSyvw0qLXzkfOuEsfAHaYVSxn9UDGDFyAH6loxP0SQS/nUqZZZf6vDf7YY7H W1zzwQACusPX7M7R/LmBi01yZE8kqTCjRM= X-Received: by 2002:a05:6a00:4fc7:b0:842:54c1:8e15 with SMTP id d2e1a72fcca58-8434ce42058mr1569469b3a.29.1781244309171; Thu, 11 Jun 2026 23:05:09 -0700 (PDT) Received: from ranjankumar.c.googlers.com.com (127.128.126.34.bc.googleusercontent.com. [34.126.128.127]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-8434b04808dsm1084616b3a.52.2026.06.11.23.05.07 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 11 Jun 2026 23:05:08 -0700 (PDT) From: Ranjan Kumar To: dmitry.torokhov@gmail.com Cc: bleung@chromium.org, bentiss@kernel.org, linux-input@vger.kernel.org, linux-kernel@vger.kernel.org, Ranjan Kumar Subject: [PATCH v4] Input: elan_i2c - prevent division by zero and arithmetic underflow Date: Fri, 12 Jun 2026 06:03:39 +0000 Message-ID: <20260612060339.3829666-1-kumarranja@chromium.org> X-Mailer: git-send-email 2.54.0.1136.gdb2ca164c4-goog In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-input@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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 --- Changes in v4: - Reverted probe fallback width back to 1. - Added check in elan_report_contact() to clamp adjusted widths to a minimum of 0, fixing the root cause of the arithmetic underflow. Changes in v3: - Changed fallback width from 1 to ETP_FWIDTH_REDUCE to prevent underflow. Changes in v2: - Added check for invalid trace values of 0 to prevent division by zero. drivers/input/mouse/elan_i2c_core.c | 36 ++++++++++++++++++++++++----- 1 file changed, 30 insertions(+), 6 deletions(-) diff --git a/drivers/input/mouse/elan_i2c_core.c b/drivers/input/mouse/elan_i2c_core.c index 5cba02a156ce..edb0a28d25aa 100644 --- a/drivers/input/mouse/elan_i2c_core.c +++ b/drivers/input/mouse/elan_i2c_core.c @@ -428,8 +428,17 @@ static int elan_query_device_parameters(struct elan_tp_data *data) if (error) return error; } - data->width_x = data->max_x / x_traces; - data->width_y = data->max_y / y_traces; + + if (!x_traces || !y_traces) { + dev_warn(&client->dev, + "invalid trace numbers: x=%u, y=%u\n", + x_traces, y_traces); + data->width_x = 1; + data->width_y = 1; + } else { + data->width_x = data->max_x / x_traces; + data->width_y = data->max_y / y_traces; + } if (device_property_read_u32(&client->dev, "touchscreen-x-mm", &x_mm) || @@ -443,8 +452,16 @@ 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 { - data->x_res = (data->max_x + 1) / x_mm; - data->y_res = (data->max_y + 1) / y_mm; + if (unlikely(x_mm == 0 || y_mm == 0)) { + dev_warn(&client->dev, + "invalid physical dimensions: x_mm=%u, y_mm=%u\n", + x_mm, y_mm); + data->x_res = 1; + data->y_res = 1; + } else { + data->x_res = (data->max_x + 1) / x_mm; + data->y_res = (data->max_y + 1) / y_mm; + } } if (device_property_read_bool(&client->dev, "elan,clickpad")) @@ -956,6 +973,7 @@ static void elan_report_contact(struct elan_tp_data *data, int contact_num, if (data->report_features & ETP_FEATURE_REPORT_MK) { unsigned int mk_x, mk_y, area_x, area_y; + int adj_width_x, adj_width_y; u8 mk_data = high_precision ? packet[ETP_MK_DATA_OFFSET + contact_num] : finger_data[3]; @@ -967,8 +985,14 @@ static void elan_report_contact(struct elan_tp_data *data, int contact_num, * To avoid treating large finger as palm, let's reduce * the width x and y per trace. */ - area_x = mk_x * (data->width_x - ETP_FWIDTH_REDUCE); - area_y = mk_y * (data->width_y - ETP_FWIDTH_REDUCE); + + adj_width_x = data->width_x > ETP_FWIDTH_REDUCE ? + data->width_x - ETP_FWIDTH_REDUCE : 0; + adj_width_y = data->width_y > ETP_FWIDTH_REDUCE ? + data->width_y - ETP_FWIDTH_REDUCE : 0; + + area_x = mk_x * adj_width_x; + area_y = mk_y * adj_width_y; input_report_abs(input, ABS_TOOL_WIDTH, mk_x); input_report_abs(input, ABS_MT_TOUCH_MAJOR, -- 2.54.0.1099.g489fc7bff1-goog