CVE-2026-89494: ocfs2: validate lengths in dlm_mig_lockres_handler

CVE-2026-89494: ocfs2: validate lengths in dlm_mig_lockres_handler

[Greg Kroah-Hartman]

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

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

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

ocfs2: validate lengths in dlm_mig_lockres_handler

A node receiving a DLM_MIG_LOCKRES message trusts several fields of the
peer-supplied dlm_migratable_lockres without validation.  num_locks and
lockname_len are bounded only on the sending side, and the message is
never checked to actually carry num_locks migratable_lock entries.  As a
result dlm_process_recovery_data() walks mres->ml[0..num_locks) past the
kmalloc(data_len) copy of the message (an out-of-bounds read that ends in
a BUG_ON panic), and dlm_init_lockres() copies lockname_len bytes into the
fixed 32-byte o2dlm_lockname slab object (a heap out-of-bounds write). 
Both are reachable by any node in the domain.

Validate these fields right after dlm_grab(), before anything uses them --
including the not-joined error path, which already prints mres->lockname
with the unbounded lockname_len as a %.*s precision.  Reject the message
unless lockname_len <= DLM_LOCKID_NAME_MAX, num_locks <=
DLM_MAX_MIGRATABLE_LOCKS (the bound the sender already asserts), and the
payload is large enough to hold the claimed locks.  Conforming recovery
and migration messages are unaffected.

The Linux kernel CVE team has assigned CVE-2026-89494 to this issue.


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

	Issue introduced in 2.6.16 with commit 6714d8e86bf443f6f7af50f9d432025649f091f5 and fixed in 6.12.109 with commit f33041906885f96e190cde54e61ddc69de39e3ee
	Issue introduced in 2.6.16 with commit 6714d8e86bf443f6f7af50f9d432025649f091f5 and fixed in 6.18.50 with commit 50c4cc9183e11f83427efbf770f54851f4471c02
	Issue introduced in 2.6.16 with commit 6714d8e86bf443f6f7af50f9d432025649f091f5 and fixed in 7.2.4 with commit a8facb1670b4a0612183198e758d9539ef628ed9
	Issue introduced in 2.6.16 with commit 6714d8e86bf443f6f7af50f9d432025649f091f5 and fixed in 7.3-rc1 with commit b54e03d9b3697d25f4a0063cf717d459c5e3ad94

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-2026-89494
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/dlm/dlmrecovery.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/f33041906885f96e190cde54e61ddc69de39e3ee
	https://git.kernel.org/stable/c/50c4cc9183e11f83427efbf770f54851f4471c02
	https://git.kernel.org/stable/c/a8facb1670b4a0612183198e758d9539ef628ed9
	https://git.kernel.org/stable/c/b54e03d9b3697d25f4a0063cf717d459c5e3ad94