linux-cve-announce - CVE-2025-68771: ocfs2: fix kernel BUG in ocfs2_find_victim

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Message-ID: <2026011357-CVE-2025-68771-cf0d@gregkh>
Date: Tue, 13 Jan 2026 16:28:57 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2025-68771: ocfs2: fix kernel BUG in ocfs2_find_victim_chain

From: Greg Kroah-Hartman <gregkh@...nel.org>

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

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

ocfs2: fix kernel BUG in ocfs2_find_victim_chain

syzbot reported a kernel BUG in ocfs2_find_victim_chain() because the
`cl_next_free_rec` field of the allocation chain list (next free slot in
the chain list) is 0, triggring the BUG_ON(!cl->cl_next_free_rec)
condition in ocfs2_find_victim_chain() and panicking the kernel.

To fix this, an if condition is introduced in ocfs2_claim_suballoc_bits(),
just before calling ocfs2_find_victim_chain(), the code block in it being
executed when either of the following conditions is true:

1. `cl_next_free_rec` is equal to 0, indicating that there are no free
chains in the allocation chain list
2. `cl_next_free_rec` is greater than `cl_count` (the total number of
chains in the allocation chain list)

Either of them being true is indicative of the fact that there are no
chains left for usage.

This is addressed using ocfs2_error(), which prints
the error log for debugging purposes, rather than panicking the kernel.

The Linux kernel CVE team has assigned CVE-2025-68771 to this issue.


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

	Fixed in 6.1.160 with commit b08a33d5f80efe6979a6e8f905c1a898910c21dd
	Fixed in 6.6.120 with commit 96f1b074c98c20f55a3b23d2ab44d9fb0f619869
	Fixed in 6.12.64 with commit e24aedae71652d4119049f1fbef6532ccbe3966d
	Fixed in 6.18.3 with commit 7acc0390e0dd7474c4451d05465a677d55ad4268
	Fixed in 6.19-rc1 with commit 039bef30e320827bac8990c9f29d2a68cd8adb5f

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-2025-68771
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/ocfs2/suballoc.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/b08a33d5f80efe6979a6e8f905c1a898910c21dd
	https://git.kernel.org/stable/c/96f1b074c98c20f55a3b23d2ab44d9fb0f619869
	https://git.kernel.org/stable/c/e24aedae71652d4119049f1fbef6532ccbe3966d
	https://git.kernel.org/stable/c/7acc0390e0dd7474c4451d05465a677d55ad4268
	https://git.kernel.org/stable/c/039bef30e320827bac8990c9f29d2a68cd8adb5f