CVE-2026-64094: batman-adv: bla: avoid NULL-ptr deref for claim via dropped interface

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

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

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

batman-adv: bla: avoid NULL-ptr deref for claim via dropped interface

Without rtnl_lock held, a hardif might be retrieved as primary interface of
a meshif, but then (while operating on this interface) getting decoupled
from the mesh interface. In this case, the meshif still exists but the
pointer from the primary hardif to the meshif is set to NULL.

The mesh_iface must be checked first to be non-NULL before continuing to
send an ARP request using meshif.

The Linux kernel CVE team has assigned CVE-2026-64094 to this issue.


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

	Issue introduced in 3.5 with commit 23721387c409087fd3b97e274f34d3ddc0970b74 and fixed in 5.10.259 with commit 4f6266735a0ba6a568b6d4c9fa51c33a5a7f2d70
	Issue introduced in 3.5 with commit 23721387c409087fd3b97e274f34d3ddc0970b74 and fixed in 5.15.210 with commit 53cb3511f6eda37d3bd923545fdba6013b6d7bb7
	Issue introduced in 3.5 with commit 23721387c409087fd3b97e274f34d3ddc0970b74 and fixed in 6.1.176 with commit efb62458c94db1fe3a287e7e89c31b0cfb03f938
	Issue introduced in 3.5 with commit 23721387c409087fd3b97e274f34d3ddc0970b74 and fixed in 6.6.143 with commit 2a8c9e86529156c62d9187b9ed9454c31665ad33
	Issue introduced in 3.5 with commit 23721387c409087fd3b97e274f34d3ddc0970b74 and fixed in 6.12.93 with commit 0f3ebd7bb417aabc44853cc7c2a184ebb0e05b45
	Issue introduced in 3.5 with commit 23721387c409087fd3b97e274f34d3ddc0970b74 and fixed in 6.18.34 with commit 6921a7683ae9ad0208d829e71f725a9e25ccff49
	Issue introduced in 3.5 with commit 23721387c409087fd3b97e274f34d3ddc0970b74 and fixed in 7.0.11 with commit 555b8d3f5c313d81d46274fd0976352dafc80124
	Issue introduced in 3.5 with commit 23721387c409087fd3b97e274f34d3ddc0970b74 and fixed in 7.1 with commit f80d3d98d2ff78d9e2fe5d68b1f45948c4f7bd24

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-2026-64094
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/batman-adv/bridge_loop_avoidance.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/4f6266735a0ba6a568b6d4c9fa51c33a5a7f2d70
	https://git.kernel.org/stable/c/53cb3511f6eda37d3bd923545fdba6013b6d7bb7
	https://git.kernel.org/stable/c/efb62458c94db1fe3a287e7e89c31b0cfb03f938
	https://git.kernel.org/stable/c/2a8c9e86529156c62d9187b9ed9454c31665ad33
	https://git.kernel.org/stable/c/0f3ebd7bb417aabc44853cc7c2a184ebb0e05b45
	https://git.kernel.org/stable/c/6921a7683ae9ad0208d829e71f725a9e25ccff49
	https://git.kernel.org/stable/c/555b8d3f5c313d81d46274fd0976352dafc80124
	https://git.kernel.org/stable/c/f80d3d98d2ff78d9e2fe5d68b1f45948c4f7bd24