CVE-2026-64091: batman-adv: tt: fix TOCTOU race for reported vlans

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

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

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

batman-adv: tt: fix TOCTOU race for reported vlans

The local TT based TVLV is generated by first checking the number of VLANs
which have at least one TT entry. A new buffer with the correct size for
the VLANs is then allocated. Only then, the list of VLANs s used to fill
the VLAN entries in the buffer. During this time, the meshif_vlan_list_lock
is held. But the actual number of TT entries of each VLAN can still
increase during this time - just not the number of VLANs in the list.

But the prefilter used in the buffer size calculation might still cause an
increase of the number of VLANs which need to be stored. Simply because a
VLAN might now suddenly have at least one entry when it had none in the
pre-alloc check - and then needs to occupy space which was not allocated.

It is better to overestimate the buffer size at the beginning and then fill
the buffer only with the VLANs which are not empty.

The Linux kernel CVE team has assigned CVE-2026-64091 to this issue.


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

	Issue introduced in 4.17 with commit 16116dac23396e73c01eeee97b102e4833a4b205 and fixed in 5.10.259 with commit e4236bf3ec8d6bb15d0d8d825dcf9933a7d6666b
	Issue introduced in 4.17 with commit 16116dac23396e73c01eeee97b102e4833a4b205 and fixed in 5.15.210 with commit 724a8eb4155669797c96b70d70e354284ae3b5a8
	Issue introduced in 4.17 with commit 16116dac23396e73c01eeee97b102e4833a4b205 and fixed in 6.1.176 with commit 211ea59988e1cba43cb0367ad65d379b56f9c3bd
	Issue introduced in 4.17 with commit 16116dac23396e73c01eeee97b102e4833a4b205 and fixed in 6.6.143 with commit 65a1e67339aa8c95ac544b796946af388930ee23
	Issue introduced in 4.17 with commit 16116dac23396e73c01eeee97b102e4833a4b205 and fixed in 6.12.93 with commit b4d4efd4e351593c81e9293d4b4408d244fa5ee7
	Issue introduced in 4.17 with commit 16116dac23396e73c01eeee97b102e4833a4b205 and fixed in 6.18.34 with commit 4cc85aec8d3c9ab4dc716dc9f1ed36fca16b227f
	Issue introduced in 4.17 with commit 16116dac23396e73c01eeee97b102e4833a4b205 and fixed in 7.0.11 with commit 9a9c859457bc440a55773e01ff18b1bb5bab6836
	Issue introduced in 4.17 with commit 16116dac23396e73c01eeee97b102e4833a4b205 and fixed in 7.1 with commit 94d27005016be15ffc638b2ecbc4d58805ad7b48
	Issue introduced in 3.16.60 with commit 3134c5a32810c510f1f447c135cec346acbb71c3
	Issue introduced in 4.4.217 with commit e861e03a1b5b615ad1b57b1802b17e260eedccfe
	Issue introduced in 4.9.217 with commit 0b81edc8818903c64c4d121bc51cd5825be8cc67
	Issue introduced in 4.14.174 with commit 90ae6475b1753f0c1a4c66034b5666de3189fac8

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-2026-64091
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/translation-table.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/e4236bf3ec8d6bb15d0d8d825dcf9933a7d6666b
	https://git.kernel.org/stable/c/724a8eb4155669797c96b70d70e354284ae3b5a8
	https://git.kernel.org/stable/c/211ea59988e1cba43cb0367ad65d379b56f9c3bd
	https://git.kernel.org/stable/c/65a1e67339aa8c95ac544b796946af388930ee23
	https://git.kernel.org/stable/c/b4d4efd4e351593c81e9293d4b4408d244fa5ee7
	https://git.kernel.org/stable/c/4cc85aec8d3c9ab4dc716dc9f1ed36fca16b227f
	https://git.kernel.org/stable/c/9a9c859457bc440a55773e01ff18b1bb5bab6836
	https://git.kernel.org/stable/c/94d27005016be15ffc638b2ecbc4d58805ad7b48