CVE-2026-72113: can: bcm: add missing device refcount for CAN filter removal

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

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

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

can: bcm: add missing device refcount for CAN filter removal

sashiko-bot remarked a problem with a concurrent device unregistration
in isotp.c which also is present in the bcm.c code. A former fix for raw.c
commit c275a176e4b6 ("can: raw: add missing refcount for memory leak fix")
introduced a netdevice_tracker which solves the issue for bcm.c too.

bcm_release(), bcm_delete_rx_op() and bcm_notifier() relied on
dev_get_by_index(ifindex) to re-find the device for an rx_op before
unregistering its filter. If a concurrent NETDEV_UNREGISTER has already
unlisted the device from the ifindex table, that lookup fails and
can_rx_unregister() is silently skipped, leaving a stale CAN filter
pointing at the soon-to-be-freed bcm_op/socket.

Hold a netdev_hold()/netdev_put() tracked reference on op->rx_reg_dev
from the moment the rx filter is registered in bcm_rx_setup() until it
is unregistered in bcm_rx_unreg(), and use that reference directly in
bcm_release() and bcm_delete_rx_op() instead of re-looking the device
up by ifindex.

The Linux kernel CVE team has assigned CVE-2026-72113 to this issue.


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

	Issue introduced in 2.6.25 with commit ffd980f976e7fd666c2e61bf8ab35107efd11828 and fixed in 6.6.148 with commit 84aa4807816e405c1bf87114fc63e06d244281ef
	Issue introduced in 2.6.25 with commit ffd980f976e7fd666c2e61bf8ab35107efd11828 and fixed in 6.12.101 with commit 633bda66fbf309f5de5e1ad6defe8e6b1d77a20f
	Issue introduced in 2.6.25 with commit ffd980f976e7fd666c2e61bf8ab35107efd11828 and fixed in 6.18.42 with commit b024c21c9066f6957b7d4a8f2037e4b000c5e041
	Issue introduced in 2.6.25 with commit ffd980f976e7fd666c2e61bf8ab35107efd11828 and fixed in 7.1.5 with commit 04d23061bbf18d5d81022eb21e9d32e99d24468d
	Issue introduced in 2.6.25 with commit ffd980f976e7fd666c2e61bf8ab35107efd11828 and fixed in 7.2-rc4 with commit d59948293ea34b6337ce2b5febab8510de70048c

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-2026-72113
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/84aa4807816e405c1bf87114fc63e06d244281ef
	https://git.kernel.org/stable/c/633bda66fbf309f5de5e1ad6defe8e6b1d77a20f
	https://git.kernel.org/stable/c/b024c21c9066f6957b7d4a8f2037e4b000c5e041
	https://git.kernel.org/stable/c/04d23061bbf18d5d81022eb21e9d32e99d24468d
	https://git.kernel.org/stable/c/d59948293ea34b6337ce2b5febab8510de70048c