CVE-2026-80820: xfs: don't livelock in scrub on a circular unlinked list

CVE-2026-80820: xfs: don't livelock in scrub on a circular unlinked list

[Greg Kroah-Hartman]

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

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

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

xfs: don't livelock in scrub on a circular unlinked list

LOLLM points out that online fsck can livelock if an unlinked inode list
contains a loop.  Use a bitmap to detect cycles.

The Linux kernel CVE team has assigned CVE-2026-80820 to this issue.


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

	Issue introduced in 4.15 with commit a12890aebb895951720ff884eab1c99a30645b29 and fixed in 6.12.106 with commit 599453f83458b57995290a1d31200c263e2c2691
	Issue introduced in 4.15 with commit a12890aebb895951720ff884eab1c99a30645b29 and fixed in 6.18.47 with commit 159d162fe80bd56573cafde5801bd5a90a3dd1ac
	Issue introduced in 4.15 with commit a12890aebb895951720ff884eab1c99a30645b29 and fixed in 7.1.11 with commit 56407a61a8bb85b884de802d39635abdb0ea7408
	Issue introduced in 4.15 with commit a12890aebb895951720ff884eab1c99a30645b29 and fixed in 7.2 with commit 527eaaefddb6ec5c83a06c9a1559960dd6361753

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-2026-80820
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/xfs/scrub/agheader.c
	fs/xfs/scrub/agheader_repair.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/599453f83458b57995290a1d31200c263e2c2691
	https://git.kernel.org/stable/c/159d162fe80bd56573cafde5801bd5a90a3dd1ac
	https://git.kernel.org/stable/c/56407a61a8bb85b884de802d39635abdb0ea7408
	https://git.kernel.org/stable/c/527eaaefddb6ec5c83a06c9a1559960dd6361753