linux-cve-announce - CVE-2025-21893: keys: Fix UAF in key

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [day] [month] [year] [list]

Message-ID: <2025033126-CVE-2025-21893-f2b4@gregkh>
Date: Mon, 31 Mar 2025 20:40:27 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: CVE-2025-21893: keys: Fix UAF in key_put()

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

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

keys: Fix UAF in key_put()

Once a key's reference count has been reduced to 0, the garbage collector
thread may destroy it at any time and so key_put() is not allowed to touch
the key after that point.  The most key_put() is normally allowed to do is
to touch key_gc_work as that's a static global variable.

However, in an effort to speed up the reclamation of quota, this is now
done in key_put() once the key's usage is reduced to 0 - but now the code
is looking at the key after the deadline, which is forbidden.

Fix this by using a flag to indicate that a key can be gc'd now rather than
looking at the key's refcount in the garbage collector.

The Linux kernel CVE team has assigned CVE-2025-21893 to this issue.

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

	Issue introduced in 6.10 with commit 9578e327b2b4935a25d49e3891b8fcca9b6c10c6 and fixed in 6.12.21 with commit 6afe2ea2daec156bd94ad2c5a6f4f4c48240dcd3
	Issue introduced in 6.10 with commit 9578e327b2b4935a25d49e3891b8fcca9b6c10c6 and fixed in 6.13.9 with commit f6a3cf833188e897c97028cd7b926e3f2cb1a8c0
	Issue introduced in 6.10 with commit 9578e327b2b4935a25d49e3891b8fcca9b6c10c6 and fixed in 6.14 with commit 75845c6c1a64483e9985302793dbf0dfa5f71e32

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-2025-21893
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:
	include/linux/key.h
	security/keys/gc.c
	security/keys/key.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/6afe2ea2daec156bd94ad2c5a6f4f4c48240dcd3
	https://git.kernel.org/stable/c/f6a3cf833188e897c97028cd7b926e3f2cb1a8c0
	https://git.kernel.org/stable/c/75845c6c1a64483e9985302793dbf0dfa5f71e32