linux-kernel - [PATCH v2] HID: wacom: Use ktime_t rather than int when dealing with timestamps

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Message-ID: <20230608213828.2108-1-jason.gerecke@wacom.com>
Date:   Thu,  8 Jun 2023 14:38:28 -0700
From:   Jason Gerecke <killertofu@...il.com>
To:     linux-input@...r.kernel.org, linux-kernel@...r.kernel.org,
        Benjamin Tissoires <benjamin.tissoires@...hat.com>,
        Jiri Kosina <jikos@...nel.org>
Cc:     Ping Cheng <pinglinux@...il.com>,
        Aaron Armstrong Skomra <skomra@...il.com>,
        Joshua Dickens <Joshua@...hua-Dickens.com>,
        Peter Hutterer <peter.hutterer@...-t.net>,
        Jason Gerecke <jason.gerecke@...om.com>, stable@...r.kernel.org
Subject: [PATCH v2] HID: wacom: Use ktime_t rather than int when dealing with timestamps

Code which interacts with timestamps needs to use the ktime_t type
returned by functions like ktime_get. The int type does not offer
enough space to store these values, and attempting to use it is a
recipe for problems. In this particular case, overflows would occur
when calculating/storing timestamps leading to incorrect values being
reported to userspace. In some cases these bad timestamps cause input
handling in userspace to appear hung.

Link: https://gitlab.freedesktop.org/libinput/libinput/-/issues/901
Fixes: 17d793f3ed53 ("HID: wacom: insert timestamp to packed Bluetooth (BT) events")
CC: stable@...r.kernel.org
Signed-off-by: Jason Gerecke <jason.gerecke@...om.com>
---
v2: Use div_u64 to perform division to deal with ARC and ARM architectures
    (as found by the kernel test robot)

 drivers/hid/wacom_wac.c | 6 +++---
 drivers/hid/wacom_wac.h | 2 +-
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/hid/wacom_wac.c b/drivers/hid/wacom_wac.c
index 2ccf838371343..174bf03908d7c 100644
--- a/drivers/hid/wacom_wac.c
+++ b/drivers/hid/wacom_wac.c
@@ -1314,7 +1314,7 @@ static void wacom_intuos_pro2_bt_pen(struct wacom_wac *wacom)
 	struct input_dev *pen_input = wacom->pen_input;
 	unsigned char *data = wacom->data;
 	int number_of_valid_frames = 0;
-	int time_interval = 15000000;
+	ktime_t time_interval = 15000000;
 	ktime_t time_packet_received = ktime_get();
 	int i;
 
@@ -1348,7 +1348,7 @@ static void wacom_intuos_pro2_bt_pen(struct wacom_wac *wacom)
 	if (number_of_valid_frames) {
 		if (wacom->hid_data.time_delayed)
 			time_interval = ktime_get() - wacom->hid_data.time_delayed;
-		time_interval /= number_of_valid_frames;
+		time_interval = div_u64(time_interval, number_of_valid_frames);
 		wacom->hid_data.time_delayed = time_packet_received;
 	}
 
@@ -1359,7 +1359,7 @@ static void wacom_intuos_pro2_bt_pen(struct wacom_wac *wacom)
 		bool range = frame[0] & 0x20;
 		bool invert = frame[0] & 0x10;
 		int frames_number_reversed = number_of_valid_frames - i - 1;
-		int event_timestamp = time_packet_received - frames_number_reversed * time_interval;
+		ktime_t event_timestamp = time_packet_received - frames_number_reversed * time_interval;
 
 		if (!valid)
 			continue;
diff --git a/drivers/hid/wacom_wac.h b/drivers/hid/wacom_wac.h
index 1a40bb8c5810c..ee21bb260f22f 100644
--- a/drivers/hid/wacom_wac.h
+++ b/drivers/hid/wacom_wac.h
@@ -324,7 +324,7 @@ struct hid_data {
 	int ps_connected;
 	bool pad_input_event_flag;
 	unsigned short sequence_number;
-	int time_delayed;
+	ktime_t time_delayed;
 };
 
 struct wacom_remote_data {
-- 
2.41.0