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

pip-izony
2025-10-23T16:31:11Z

From: Seungjin Bae <eeodqql09@gmail.com>

`kvaser_usb_leaf_wait_cmd()` and `kvaser_usb_leaf_read_bulk_callback`
functions contain logic to handle 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@gmail.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