CVE-2026-72117can: bcm: fix data race on rx_stamp/rx_ifindex in bcm_rx_handler()

Official description

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.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/b64f60c468d149aca22ea56bb842b9730215aaa5
• https://git.kernel.org/stable/c/c8a5d7cb095d3b12bd9dcf752d6ca0ff50872ac5
• https://git.kernel.org/stable/c/4b97410f4bba18d2ee2784c8e089104f387bc27c
• https://git.kernel.org/stable/c/5f246b96ab47523ec9b8ea870b5c567a3cb1eb1c
• https://git.kernel.org/stable/c/656ff69ef235699035e57d9e1ae417e62a38aa7f
• https://git.kernel.org/stable/c/136de17f38630307991c59aa7080012a99451783
• https://git.kernel.org/stable/c/c312b750bb5ac3348cfc85dab25e90937bd4d251
• https://git.kernel.org/stable/c/58fd6cbc8541216af1d7ed272ea7ac2b66d50fd8