linux-kernel - [PATCH] can: kvaser_usb: leaf: Fix infinite loop on zero-length cmd

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Message-ID: <20251023003908.130468-2-eeodqql09@gmail.com>
Date: Wed, 22 Oct 2025 20:39:09 -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] can: kvaser_usb: leaf: Fix infinite loop on zero-length cmd

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

The `kvaser_usb_leaf_read_bulk_callback()` function parse received
command buffers from the device. The firmware may insert zero-length
placeholder commands to handle alignment with the USB endpoint's
wMaxPacketSize.

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.

I fixed 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>
---
 drivers/net/can/usb/kvaser_usb/kvaser_usb_leaf.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

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..4da6d4ba4e1e 100644
--- a/drivers/net/can/usb/kvaser_usb/kvaser_usb_leaf.c
+++ b/drivers/net/can/usb/kvaser_usb/kvaser_usb_leaf.c
@@ -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