linux-cve-announce - CVE-2024-38570: gfs2: Fix potential glock use-after-free on unmount

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Message-ID: <2024061956-CVE-2024-38570-a8ef@gregkh>
Date: Wed, 19 Jun 2024 15:36:19 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: CVE-2024-38570: gfs2: Fix potential glock use-after-free on unmount

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

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

gfs2: Fix potential glock use-after-free on unmount

When a DLM lockspace is released and there ares still locks in that
lockspace, DLM will unlock those locks automatically.  Commit
fb6791d100d1b started exploiting this behavior to speed up filesystem
unmount: gfs2 would simply free glocks it didn't want to unlock and then
release the lockspace.  This didn't take the bast callbacks for
asynchronous lock contention notifications into account, which remain
active until until a lock is unlocked or its lockspace is released.

To prevent those callbacks from accessing deallocated objects, put the
glocks that should not be unlocked on the sd_dead_glocks list, release
the lockspace, and only then free those glocks.

As an additional measure, ignore unexpected ast and bast callbacks if
the receiving glock is dead.

The Linux kernel CVE team has assigned CVE-2024-38570 to this issue.

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

	Issue introduced in 3.8 with commit fb6791d100d1 and fixed in 6.6.33 with commit 0636b34b4458
	Issue introduced in 3.8 with commit fb6791d100d1 and fixed in 6.8.12 with commit e42e8a24d7f0
	Issue introduced in 3.8 with commit fb6791d100d1 and fixed in 6.9.3 with commit 501cd8fabf62
	Issue introduced in 3.8 with commit fb6791d100d1 and fixed in 6.10-rc1 with commit d98779e68772

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-2024-38570
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:
	fs/gfs2/glock.c
	fs/gfs2/glock.h
	fs/gfs2/incore.h
	fs/gfs2/lock_dlm.c
	fs/gfs2/ops_fstype.c
	fs/gfs2/super.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/0636b34b44589b142700ac137b5f69802cfe2e37
	https://git.kernel.org/stable/c/e42e8a24d7f02d28763d16ca7ec5fc6d1f142af0
	https://git.kernel.org/stable/c/501cd8fabf621d10bd4893e37f6ce6c20523c8ca
	https://git.kernel.org/stable/c/d98779e687726d8f8860f1c54b5687eec5f63a73