CVE-2026-72115: can: bcm: track a single source interface for ANYDEV timeout/throttle ops

From: Greg Kroah-Hartman <[email protected]>

Description
===========

In the Linux kernel, the following vulnerability has been resolved:

can: bcm: track a single source interface for ANYDEV timeout/throttle ops

An ANYDEV rx op (ifindex == 0) with an active RX timeout and/or
throttle timer has no defined semantics when matching frames arrive
from several interfaces: bcm_rx_handler() can run concurrently for
the same op on different CPUs, racing hrtimer_cancel()/
bcm_rx_starttimer() against bcm_rx_timeout_handler() and causing
spurious RX_TIMEOUT notifications and last_frames corruption. The
same concurrency lets throttled multiplex frames from different
interfaces clobber the single rx_ifindex/rx_stamp fields shared by
the op.

Add op->if_detected to track the first interface that delivers a
matching frame while a timeout/throttle timer is configured, and
reject frames from any other interface for that op. The claim is
decided in bcm_rx_handler() before hrtimer_cancel() touches
op->timer, so a rejected frame can never disturb the claimed
interface's watchdog. RTR-mode ops are excluded via RX_RTR_FRAME,
independent of kt_ival1/kt_ival2, since those may briefly hold a
stale value from an earlier non-RTR configuration.

The claim is released in bcm_notify() on NETDEV_UNREGISTER and in
bcm_rx_setup() when SETTIMER reconfigures the timer values.

A (re-)claim is only possible on CAN devices in NETREG_REGISTERED
dev->reg_state to cover the release in bcm_notify() where reg_state
becomes NETREG_UNREGISTERING until synchronize_net().

The Linux kernel CVE team has assigned CVE-2026-72115 to this issue.


Affected and fixed versions
===========================

	Issue introduced in 2.6.25 with commit ffd980f976e7fd666c2e61bf8ab35107efd11828 and fixed in 6.6.148 with commit 18b45251e74e35668f0dd0c470549384ae191ecf
	Issue introduced in 2.6.25 with commit ffd980f976e7fd666c2e61bf8ab35107efd11828 and fixed in 6.12.101 with commit 3ff8c24b421070a2db99a5cdb86edc9ff339418e
	Issue introduced in 2.6.25 with commit ffd980f976e7fd666c2e61bf8ab35107efd11828 and fixed in 6.18.42 with commit eca8b44d51fc6ab61022258ec968e55e3073b79e
	Issue introduced in 2.6.25 with commit ffd980f976e7fd666c2e61bf8ab35107efd11828 and fixed in 7.1.5 with commit b6317022b685a430a3ae420456716e3c0c02ef4b
	Issue introduced in 2.6.25 with commit ffd980f976e7fd666c2e61bf8ab35107efd11828 and fixed in 7.2-rc4 with commit 2f5976f54a04e9f18b25283036ac3136be453b17

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2026-72115
will be updated if fixes are backported, please check that for the most
up to date information about this issue.


Affected files
==============

The file(s) affected by this issue are:
	net/can/bcm.c


Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/18b45251e74e35668f0dd0c470549384ae191ecf
	https://git.kernel.org/stable/c/3ff8c24b421070a2db99a5cdb86edc9ff339418e
	https://git.kernel.org/stable/c/eca8b44d51fc6ab61022258ec968e55e3073b79e
	https://git.kernel.org/stable/c/b6317022b685a430a3ae420456716e3c0c02ef4b
	https://git.kernel.org/stable/c/2f5976f54a04e9f18b25283036ac3136be453b17