linux-kernel - [PATCH v2] can: kvaser_usb: leaf: Fix potential infinite loop in command parsers

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Message-ID: <20251023162709.348240-1-eeodqql09@gmail.com>
Date: Thu, 23 Oct 2025 12:27:09 -0400
From: pip-izony <eeodqql09@...il.com>
To: Marc Kleine-Budde <mkl@...gutronix.de>,
	Vincent Mailhol <mailhol@...nel.org>
Cc: Seungjin Bae <eeodqql09@...il.com>,
	Kyungtae Kim <Kyungtae.Kim@...tmouth.edu>,
	Jimmy Assarsson <extja@...ser.com>,
	linux-can@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH v2] can: kvaser_usb: leaf: Fix potential infinite loop in command parsers

From: Seungjin Bae <eeodqql09@...il.com>

The `kvaser_usb_leaf_wait_cmd()` and `kvaser_usb_leaf_read_bulk_callback`
functions contain logic to zero-length commands. These commands are used
to align data to the USB endpoint's wMaxPacketSize boundary.

The driver attempts to skip these placeholders by aligning the buffer
position `pos` to the next packet boundary using `round_up()` function.

However, if zero-length command is found exactly on a packet boundary
(i.e., `pos` is a multiple of wMaxPacketSize, including 0), `round_up`
function will return the unchanged value of `pos`. This prevents `pos`
to be increased, causing an infinite loop in the parsing logic.

This patch fixes this in the function by using `pos + 1` instead.
This ensures that even if `pos` is on a boundary, the calculation is
based on `pos + 1`, forcing `round_up()` to always return the next
aligned boundary.

Fixes: 7259124eac7d ("can: kvaser_usb: Split driver into kvaser_usb_core.c and kvaser_usb_leaf.c")
Signed-off-by: Seungjin Bae <eeodqql09@...il.com>
---
 v1 -> v2: Apply the same infinite loop fix to kvaser_usb_leaf_wait_cmd()

 drivers/net/can/usb/kvaser_usb/kvaser_usb_leaf.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/net/can/usb/kvaser_usb/kvaser_usb_leaf.c b/drivers/net/can/usb/kvaser_usb/kvaser_usb_leaf.c
index c29828a94ad0..1167d38344f1 100644
--- a/drivers/net/can/usb/kvaser_usb/kvaser_usb_leaf.c
+++ b/drivers/net/can/usb/kvaser_usb/kvaser_usb_leaf.c
@@ -685,7 +685,7 @@ static int kvaser_usb_leaf_wait_cmd(const struct kvaser_usb *dev, u8 id,
 			 * for further details.
 			 */
 			if (tmp->len == 0) {
-				pos = round_up(pos,
+				pos = round_up(pos + 1,
 					       le16_to_cpu
 						(dev->bulk_in->wMaxPacketSize));
 				continue;
@@ -1732,7 +1732,7 @@ static void kvaser_usb_leaf_read_bulk_callback(struct kvaser_usb *dev,
 		 * number of events in case of a heavy rx load on the bus.
 		 */
 		if (cmd->len == 0) {
-			pos = round_up(pos, le16_to_cpu
+			pos = round_up(pos + 1, le16_to_cpu
 						(dev->bulk_in->wMaxPacketSize));
 			continue;
 		}
-- 
2.43.0