From 1e446fd0582ad8be9f6dafb115fc2e7245f9bea7 Mon Sep 17 00:00:00 2001 From: Greg Kroah-Hartman Date: Mon, 23 Feb 2026 17:30:20 +0100 Subject: [PATCH] can: ucan: Fix infinite loop from zero-length messages If a broken ucan device gets a message with the message length field set to 0, then the driver will loop for forever in ucan_read_bulk_callback(), hanging the system. If the length is 0, just skip the message and go on to the next one. This has been fixed in the kvaser_usb driver in the past in commit 0c73772cd2b8 ("can: kvaser_usb: leaf: Fix potential infinite loop in command parsers"), so there must be some broken devices out there like this somewhere. Cc: Marc Kleine-Budde Cc: Vincent Mailhol Cc: stable@kernel.org Assisted-by: gkh_clanker_2000 Signed-off-by: Greg Kroah-Hartman Link: https://patch.msgid.link/2026022319-huff-absurd-6a18@gregkh Fixes: 9f2d3eae88d2 ("can: ucan: add driver for Theobroma Systems UCAN devices") Signed-off-by: Marc Kleine-Budde --- drivers/net/can/usb/ucan.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/net/can/usb/ucan.c b/drivers/net/can/usb/ucan.c index c79508b1c43e..0ea0ac75e42f 100644 --- a/drivers/net/can/usb/ucan.c +++ b/drivers/net/can/usb/ucan.c @@ -748,7 +748,7 @@ static void ucan_read_bulk_callback(struct urb *urb) len = le16_to_cpu(m->len); /* check sanity (length of content) */ - if (urb->actual_length - pos < len) { + if ((len == 0) || (urb->actual_length - pos < len)) { netdev_warn(up->netdev, "invalid message (short; no data; l:%d)\n", urb->actual_length);