linux-cve-announce - CVE-2024-50257: netfilter: Fix use-after-free in get

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Message-ID: <2024110939-CVE-2024-50257-af5f@gregkh>
Date: Sat,  9 Nov 2024 11:16:05 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: CVE-2024-50257: netfilter: Fix use-after-free in get_info()

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

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

netfilter: Fix use-after-free in get_info()

ip6table_nat module unload has refcnt warning for UAF. call trace is:

WARNING: CPU: 1 PID: 379 at kernel/module/main.c:853 module_put+0x6f/0x80
Modules linked in: ip6table_nat(-)
CPU: 1 UID: 0 PID: 379 Comm: ip6tables Not tainted 6.12.0-rc4-00047-gc2ee9f594da8-dirty #205
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996),
BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014
RIP: 0010:module_put+0x6f/0x80
Call Trace:
 <TASK>
 get_info+0x128/0x180
 do_ip6t_get_ctl+0x6a/0x430
 nf_getsockopt+0x46/0x80
 ipv6_getsockopt+0xb9/0x100
 rawv6_getsockopt+0x42/0x190
 do_sock_getsockopt+0xaa/0x180
 __sys_getsockopt+0x70/0xc0
 __x64_sys_getsockopt+0x20/0x30
 do_syscall_64+0xa2/0x1a0
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Concurrent execution of module unload and get_info() trigered the warning.
The root cause is as follows:

cpu0				      cpu1
module_exit
//mod->state = MODULE_STATE_GOING
  ip6table_nat_exit
    xt_unregister_template
	kfree(t)
	//removed from templ_list
				      getinfo()
					  t = xt_find_table_lock
						list_for_each_entry(tmpl, &xt_templates[af]...)
							if (strcmp(tmpl->name, name))
								continue;  //table not found
							try_module_get
						list_for_each_entry(t, &xt_net->tables[af]...)
							return t;  //not get refcnt
					  module_put(t->me) //uaf
    unregister_pernet_subsys
    //remove table from xt_net list

While xt_table module was going away and has been removed from
xt_templates list, we couldnt get refcnt of xt_table->me. Check
module in xt_net->tables list re-traversal to fix it.

The Linux kernel CVE team has assigned CVE-2024-50257 to this issue.


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

	Issue introduced in 5.15 with commit fdacd57c79b7 and fixed in 5.15.171 with commit ba22ea013483
	Issue introduced in 5.15 with commit fdacd57c79b7 and fixed in 6.1.116 with commit cb7c388b5967
	Issue introduced in 5.15 with commit fdacd57c79b7 and fixed in 6.6.60 with commit 6a1f088f9807
	Issue introduced in 5.15 with commit fdacd57c79b7 and fixed in 6.11.7 with commit bab3bb35c03b
	Issue introduced in 5.15 with commit fdacd57c79b7 and fixed in 6.12-rc6 with commit f48d258f0ac5

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-2024-50257
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/netfilter/x_tables.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/ba22ea01348384df19cc1fabc7964be6e7189749
	https://git.kernel.org/stable/c/cb7c388b5967946f097afdb759b7c860305f2d96
	https://git.kernel.org/stable/c/6a1f088f9807f5166f58902d26246d0b88da03a8
	https://git.kernel.org/stable/c/bab3bb35c03b263c486833d50d50c081d9e9832b
	https://git.kernel.org/stable/c/f48d258f0ac540f00fa617dac496c4c18b5dc2fa