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([187.13.206.89]) by smtp.gmail.com with ESMTPSA id 71dfb90a1353d-5c84714c380sm15063108e0c.15.2026.09.15.07.52.45 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 15 Sep 2026 07:52:47 -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 v3] HID: wacom: avoid overflows in sequence number tracking Date: Tue, 15 Sep 2026 11:52:29 -0300 Message-ID: <20260915145229.3036596-1-qwe.aldo@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20260915111448.2726869-1-qwe.aldo@gmail.com> References: <20260915111448.2726869-1-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 The dropped-packet calculation derives the sequence range in signed int arithmetic. A sequence field whose logical range spans all 32-bit values makes the range calculation wrap to zero, so the following modulo triggers a divide exception. Normalize the maximum and current value according to the HID parser's signedness rule, and keep the sequence state and arithmetic in s64. Use div64_s64() for the remainder to avoid __moddi3 link failures on 32-bit architectures. This also avoids overflowing value + 1 at the logical maximum. Fixes: 359673ea3a20 ("HID: wacom: Support sequence numbers smaller than 16-bit") Cc: stable@vger.kernel.org Signed-off-by: Aldo Ariel Panzardo --- Changes in v3: - Replace raw s64 modulo with div64_s64()-based remainder to avoid __moddi3 link failure on 32-bit architectures (i386, arm32). Reported by Sashiko AI review. Changes in v2: - Normalize logical_maximum/value as unsigned when logical_minimum >= 0, matching HID parser signedness. Store sequence state as s64. Fixes unsigned 0..UINT32_MAX range that broke v1. drivers/hid/wacom_wac.c | 33 ++++++++++++++++++++++++--------- drivers/hid/wacom_wac.h | 2 +- 2 files changed, 25 insertions(+), 10 deletions(-) diff --git a/drivers/hid/wacom_wac.c b/drivers/hid/wacom_wac.c index da1f0ea856..af94f59a5d 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 @@ -2527,18 +2528,33 @@ static void wacom_wac_pen_event(struct hid_device *hdev, struct hid_field *field case WACOM_HID_WD_BARRELSWITCH3: wacom_wac->hid_data.barrelswitch3 = value; return; - case WACOM_HID_WD_SEQUENCENUMBER: - if (wacom_wac->hid_data.sequence_number != value && + case WACOM_HID_WD_SEQUENCENUMBER: { + s64 sequence_minimum = field->logical_minimum; + s64 sequence_maximum = sequence_minimum < 0 ? + (s64)field->logical_maximum : + (s64)(u32)field->logical_maximum; + s64 sequence_value = sequence_minimum < 0 ? + (s64)value : (s64)(u32)value; + + if (wacom_wac->hid_data.sequence_number != sequence_value && wacom_wac->hid_data.sequence_number >= 0) { - int sequence_size = field->logical_maximum - field->logical_minimum + 1; - int drop_count = (value - wacom_wac->hid_data.sequence_number) % sequence_size; - hid_warn(hdev, "Dropped %d packets", drop_count); + s64 sequence_size = sequence_maximum - + sequence_minimum + 1; + s64 drop_count = sequence_value - + wacom_wac->hid_data.sequence_number; + + drop_count -= div64_s64(drop_count, sequence_size) * + sequence_size; + if (drop_count < 0) + drop_count += sequence_size; + hid_warn(hdev, "Dropped %lld packets", + (long long)drop_count); } - wacom_wac->hid_data.sequence_number = value + 1; - if (wacom_wac->hid_data.sequence_number > field->logical_maximum) - wacom_wac->hid_data.sequence_number = field->logical_minimum; + if (sequence_value >= sequence_maximum) + wacom_wac->hid_data.sequence_number = sequence_minimum; + else + wacom_wac->hid_data.sequence_number = sequence_value + 1; return; } + } /* send pen events only when touch is up or forced out * or touch arbitration is off diff --git a/drivers/hid/wacom_wac.h b/drivers/hid/wacom_wac.h index 126bec6e5c..74e7c5a04a 100644 --- a/drivers/hid/wacom_wac.h +++ b/drivers/hid/wacom_wac.h @@ -324,7 +324,7 @@ struct hid_data { int bat_connected; int ps_connected; bool pad_input_event_flag; - int sequence_number; + s64 sequence_number; ktime_t time_delayed; }; -- 2.43.0