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([187.13.206.89]) by smtp.gmail.com with ESMTPSA id 71dfb90a1353d-5c8470e7ef4sm14528090e0c.9.2026.09.14.21.25.56 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 14 Sep 2026 21:25:58 -0700 (PDT) From: Aldo Ariel Panzardo To: Jiri Kosina , Benjamin Tissoires Cc: Ping Cheng , Jason Gerecke , linux-input@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org, Aldo Ariel Panzardo Subject: [PATCH v2] HID: wacom: validate battery range before scaling Date: Tue, 15 Sep 2026 01:25:46 -0300 Message-ID: <20260915042546.2454238-1-qwe.aldo@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20260915041248.2432629-1-qwe.aldo@gmail.com> References: <20260915041248.2432629-1-qwe.aldo@gmail.com> Precedence: bulk X-Mailing-List: linux-input@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Battery events divide by the difference between the logical maximum and minimum without validating the range. A malformed HID descriptor with equal limits can therefore trigger a divide-by-zero exception. Move percentage conversion to a helper that widens the arithmetic, rejects non-positive ranges, and accounts for a nonzero logical minimum. Clamp the result to [0, 100] instead of rejecting out-of-range values, so that real hardware whose ADC occasionally reports slightly beyond its declared limits still registers its battery and updates capacity normally. Fixes: 37d160193834 ("HID: wacom: generic: Scale battery capacity measurements to percentages") Cc: stable@vger.kernel.org Signed-off-by: Aldo Ariel Panzardo --- Changes in v2: - Clamp the computed percentage to [0, 100] instead of returning false, so that slightly out-of-range ADC values do not prevent battery registration (WACOM_QUIRK_BATTERY) or silently drop updates. Reported by Sashiko AI review. drivers/hid/wacom_wac.c | 23 +++++++++++++++++++++-- 1 file changed, 21 insertions(+), 2 deletions(-) diff --git a/drivers/hid/wacom_wac.c b/drivers/hid/wacom_wac.c index da1f0ea85..XXXXXXX 100644 --- a/drivers/hid/wacom_wac.c +++ b/drivers/hid/wacom_wac.c @@ -7,6 +7,7 @@ #include "wacom.h" #include #include +#include /* resolution for penabled devices */ #define WACOM_PL_RES 20 @@ -1937,6 +1938,22 @@ static void wacom_wac_battery_usage_mapping(struct hid_device *hdev, return; } +static __s32 wacom_wac_battery_percentage(struct hid_field *field, __s32 value) +{ + s64 range = (s64)field->logical_maximum - field->logical_minimum; + s64 result; + + if (range <= 0) + return 0; + + result = div64_s64(((s64)value - field->logical_minimum) * 100, + range); + + return clamp_val(result, 0, 100); +} + static void wacom_wac_battery_event(struct hid_device *hdev, struct hid_field *field, struct hid_usage *usage, __s32 value) { @@ -1950,7 +1967,8 @@ static void wacom_wac_battery_event(struct hid_device *hdev, struct hid_field *f wacom_wac->hid_data.bat_status = POWER_SUPPLY_STATUS_UNKNOWN; } else { - value = value * 100 / (field->logical_maximum - field->logical_minimum); + value = wacom_wac_battery_percentage(field, value); wacom_wac->hid_data.battery_capacity = value; wacom_wac->hid_data.bat_connected = 1; wacom_wac->hid_data.bat_status = WACOM_POWER_SUPPLY_STATUS_AUTO; @@ -1958,7 +1976,8 @@ static void wacom_wac_battery_event(struct hid_device *hdev, struct hid_field *f wacom_wac->features.quirks |= WACOM_QUIRK_BATTERY; break; case WACOM_HID_WD_BATTERY_LEVEL: - value = value * 100 / (field->logical_maximum - field->logical_minimum); + value = wacom_wac_battery_percentage(field, value); wacom_wac->hid_data.battery_capacity = value; wacom_wac->hid_data.bat_connected = 1; wacom_wac->hid_data.bat_status = WACOM_POWER_SUPPLY_STATUS_AUTO; -- 2.43.0