On 04.08.2022 10:14:11, Sebastian Würl wrote: > The mcp251x driver uses both receiving mailboxes of the CAN controller > chips. For retrieving the CAN frames from the controller via SPI, it checks > once per interrupt which mailboxes have been filled and will retrieve the > messages accordingly. > > This introduces a race condition, as another CAN frame can enter mailbox 1 > while mailbox 0 is emptied. If now another CAN frame enters mailbox 0 until > the interrupt handler is called next, mailbox 0 is emptied before > mailbox 1, leading to out-of-order CAN frames in the network device. > > This is fixed by checking the interrupt flags once again after freeing > mailbox 0, to correctly also empty mailbox 1 before leaving the handler. > > For reproducing the bug I created the following setup: > - Two CAN devices, one Raspberry Pi with MCP2515, the other can be any. > - Setup CAN to 1 MHz > - Spam bursts of 5 CAN-messages with increasing CAN-ids > - Continue sending the bursts while sleeping a second between the bursts > - Check on the RPi whether the received messages have increasing CAN-ids > - Without this patch, every burst of messages will contain a flipped pair > > Fixes: bf66f3736a94 ("can: mcp251x: Move to threaded interrupts instead of workqueues.") > Signed-off-by: Sebastian Würl I've reduced the scope of intf1, eflag1 while applying the patch to can-next/master. Thanks, Marc -- Pengutronix e.K. | Marc Kleine-Budde | Embedded Linux | https://www.pengutronix.de | Vertretung West/Dortmund | Phone: +49-231-2826-924 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |