cve/published/2024/CVE-2024-53211.mbox

From bippy-5f407fcff5a0 Mon Sep 17 00:00:00 2001
From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: <linux-cve-announce@vger.kernel.org>
Reply-to: <cve@kernel.org>, <linux-kernel@vger.kernel.org>
Subject: CVE-2024-53211: net/l2tp: fix warning in l2tp_exit_net found by syzbot

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

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

net/l2tp: fix warning in l2tp_exit_net found by syzbot

In l2tp's net exit handler, we check that an IDR is empty before
destroying it:

	WARN_ON_ONCE(!idr_is_empty(&pn->l2tp_tunnel_idr));
	idr_destroy(&pn->l2tp_tunnel_idr);

By forcing memory allocation failures in idr_alloc_32, syzbot is able
to provoke a condition where idr_is_empty returns false despite there
being no items in the IDR. This turns out to be because the radix tree
of the IDR contains only internal radix-tree nodes and it is this that
causes idr_is_empty to return false. The internal nodes are cleaned by
idr_destroy.

Use idr_for_each to check that the IDR is empty instead of
idr_is_empty to avoid the problem.

The Linux kernel CVE team has assigned CVE-2024-53211 to this issue.


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

	Issue introduced in 6.12 with commit 73d33bd063c4cfef3db17f9bec3d202928ed8631 and fixed in 6.12.2 with commit a487cc8986d6dd75b60b59004f3bd2ea9b4dd541
	Issue introduced in 6.12 with commit 73d33bd063c4cfef3db17f9bec3d202928ed8631 and fixed in 6.13 with commit 5d066766c5f1252f98ff859265bcd1a5b52ac46c

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-2024-53211
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/l2tp/l2tp_core.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/a487cc8986d6dd75b60b59004f3bd2ea9b4dd541
	https://git.kernel.org/stable/c/5d066766c5f1252f98ff859265bcd1a5b52ac46c