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

[Jimmy Assarsson <extja@kvaser.com>]

Hi Seungjin,

Thanks for fixing this!
I'll do some testing in the beginning of next week.
Which Kvaser device did you use when you discovered the problem?

Best regards,
jimmy

On 10/23/25 18:27, pip-izony wrote:
> From: Seungjin Bae <eeodqql09@gmail.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@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;
>   		}