CVE-2026-64093: batman-adv: tp_meter: directly shut down timer on cleanup

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

From: Greg Kroah-Hartman <gregkh@kernel.org>

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

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

batman-adv: tp_meter: directly shut down timer on cleanup

batadv_tp_sender_cleanup() was calling timer_delete_sync() followed by
timer_delete() to guard against the timer handler re-arming itself between
the two calls. This double-deletion hack relied on the sending status being
set to 0 to suppress re-arming.

Replace both calls with a single timer_shutdown_sync(). This function both
waits for any running timer callback to complete (like timer_delete_sync())
and permanently disarms the timer so it cannot be re-armed afterwards,
making re-arming prevention unconditional and self-documenting.

The re-arming property is also required because otherwise:

1. context 0 (batadv_tp_recv_ack()) checks in
   batadv_tp_reset_sender_timer() if sending is still 1 -> it is
2. context 1 changes in batadv_tp_sender_shutdown() sending to 0 and in
   this process forces the kthread to stop timer in
   batadv_tp_sender_cleanup()
3. context 0 continues in batadv_tp_reset_sender_timer() and rearms the
   timer -> but the reference for it is already gone

The Linux kernel CVE team has assigned CVE-2026-64093 to this issue.


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

	Issue introduced in 4.8 with commit 33a3bb4a3345bb511f9c69c913da95d4693e2a4e and fixed in 5.15.210 with commit 00bf4bb9947b1190a8be8d9b6a1bcbfa3707785c
	Issue introduced in 4.8 with commit 33a3bb4a3345bb511f9c69c913da95d4693e2a4e and fixed in 6.1.176 with commit 74a76634055462833446684fd526d73c290ea43a
	Issue introduced in 4.8 with commit 33a3bb4a3345bb511f9c69c913da95d4693e2a4e and fixed in 6.6.143 with commit 5bc2d50fb66b46f86543d5153a188eb1486d0b6e
	Issue introduced in 4.8 with commit 33a3bb4a3345bb511f9c69c913da95d4693e2a4e and fixed in 6.12.93 with commit f86b20ec8d17d77bddc02c5c86cfa2389d84ecff
	Issue introduced in 4.8 with commit 33a3bb4a3345bb511f9c69c913da95d4693e2a4e and fixed in 6.18.34 with commit 770bf0a35f0620b526fd4193889d1e77084e4c43
	Issue introduced in 4.8 with commit 33a3bb4a3345bb511f9c69c913da95d4693e2a4e and fixed in 7.0.11 with commit 933880a8bc9b4042223a79255c0b1021cdc36991
	Issue introduced in 4.8 with commit 33a3bb4a3345bb511f9c69c913da95d4693e2a4e and fixed in 7.1 with commit d5487249a81ea658717614009c8f46acc5b7101a

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-2026-64093
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/tp_meter.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/00bf4bb9947b1190a8be8d9b6a1bcbfa3707785c
	https://git.kernel.org/stable/c/74a76634055462833446684fd526d73c290ea43a
	https://git.kernel.org/stable/c/5bc2d50fb66b46f86543d5153a188eb1486d0b6e
	https://git.kernel.org/stable/c/f86b20ec8d17d77bddc02c5c86cfa2389d84ecff
	https://git.kernel.org/stable/c/770bf0a35f0620b526fd4193889d1e77084e4c43
	https://git.kernel.org/stable/c/933880a8bc9b4042223a79255c0b1021cdc36991
	https://git.kernel.org/stable/c/d5487249a81ea658717614009c8f46acc5b7101a