linux-cve-announce - CVE-2024-50212: lib: alloc_tag_module_unload must wait for pending kfree

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Message-ID: <2024110921-CVE-2024-50212-74b8@gregkh>
Date: Sat,  9 Nov 2024 11:15:20 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: CVE-2024-50212: lib: alloc_tag_module_unload must wait for pending kfree_rcu calls

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

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

lib: alloc_tag_module_unload must wait for pending kfree_rcu calls

Ben Greear reports following splat:
 ------------[ cut here ]------------
 net/netfilter/nf_nat_core.c:1114 module nf_nat func:nf_nat_register_fn has 256 allocated at module unload
 WARNING: CPU: 1 PID: 10421 at lib/alloc_tag.c:168 alloc_tag_module_unload+0x22b/0x3f0
 Modules linked in: nf_nat(-) btrfs ufs qnx4 hfsplus hfs minix vfat msdos fat
...
 Hardware name: Default string Default string/SKYBAY, BIOS 5.12 08/04/2020
 RIP: 0010:alloc_tag_module_unload+0x22b/0x3f0
  codetag_unload_module+0x19b/0x2a0
  ? codetag_load_module+0x80/0x80

nf_nat module exit calls kfree_rcu on those addresses, but the free
operation is likely still pending by the time alloc_tag checks for leaks.

Wait for outstanding kfree_rcu operations to complete before checking
resolves this warning.

Reproducer:
unshare -n iptables-nft -t nat -A PREROUTING -p tcp
grep nf_nat /proc/allocinfo # will list 4 allocations
rmmod nft_chain_nat
rmmod nf_nat                # will WARN.

[akpm@...ux-foundation.org: add comment]

The Linux kernel CVE team has assigned CVE-2024-50212 to this issue.


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

	Issue introduced in 6.10 with commit a473573964e5 and fixed in 6.11.7 with commit 24211fb49c9a
	Issue introduced in 6.10 with commit a473573964e5 and fixed in 6.12-rc4 with commit dc783ba4b9df

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-2024-50212
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:
	lib/codetag.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/24211fb49c9ac1b576470b7e393a5a0b50af2707
	https://git.kernel.org/stable/c/dc783ba4b9df3fb3e76e968b2cbeb9960069263c