In the Linux kernel, the following vulnerability has been resolved:
can: bcm: fix data race on rx_stamp/rx_ifindex in bcm_rx_handler()
For an rx op subscribed on all interfaces (ifindex == 0), the same op is registered once in the shared per-netns wildcard filter list, so bcm_rx_handler() can run concurrently on different CPUs for frames arriving on different net devices.
op->rx_stamp and op->rx_ifindex were written before bcm_rx_update_lock was taken, allowing concurrent writers to race each other - including a torn store of the 64-bit rx_stamp on 32-bit platforms.
Beyond a torn store bcm_send_to_user() must report the timestamp/ifindex of the very same frame whose content it is delivering. So the assignment is placed in the same unbroken bcm_rx_update_lock section as the content comparison.
As a side effect, the RTR-request frame feature (which never reach bcm_send_to_user()) no longer updates rx_stamp/rx_ifindex, since only the notification path needs them.
References
- https://git.kernel.org/stable/c/136de17f38630307991c59aa7080012a99451783
- https://git.kernel.org/stable/c/58fd6cbc8541216af1d7ed272ea7ac2b66d50fd8
- https://git.kernel.org/stable/c/5f246b96ab47523ec9b8ea870b5c567a3cb1eb1c
- https://git.kernel.org/stable/c/656ff69ef235699035e57d9e1ae417e62a38aa7f
- https://git.kernel.org/stable/c/c312b750bb5ac3348cfc85dab25e90937bd4d251