Message-ID: <2025120938-CVE-2023-53777-f842@gregkh>
Date: Tue,  9 Dec 2025 09:01:58 +0900
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2023-53777: erofs: kill hooked chains to avoid loops on deduplicated compressed images

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

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

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

erofs: kill hooked chains to avoid loops on deduplicated compressed images

After heavily stressing EROFS with several images which include a
hand-crafted image of repeated patterns for more than 46 days, I found
two chains could be linked with each other almost simultaneously and
form a loop so that the entire loop won't be submitted.  As a
consequence, the corresponding file pages will remain locked forever.

It can be _only_ observed on data-deduplicated compressed images.
For example, consider two chains with five pclusters in total:
	Chain 1:  2->3->4->5    -- The tail pcluster is 5;
        Chain 2:  5->1->2       -- The tail pcluster is 2.

Chain 2 could link to Chain 1 with pcluster 5; and Chain 1 could link
to Chain 2 at the same time with pcluster 2.

Since hooked chains are all linked locklessly now, I have no idea how
to simply avoid the race.  Instead, let's avoid hooked chains completely
until I could work out a proper way to fix this and end users finally
tell us that it's needed to add it back.

Actually, this optimization can be found with multi-threaded workloads
(especially even more often on deduplicated compressed images), yet I'm
not sure about the overall system impacts of not having this compared
with implementation complexity.

The Linux kernel CVE team has assigned CVE-2023-53777 to this issue.


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

	Issue introduced in 6.0 with commit 267f2492c8f71dac44399988b510f9bf6b074a51 and fixed in 6.1.39 with commit d3b39ea24835ac03da1a30f93ae7c05d55a40191
	Issue introduced in 6.0 with commit 267f2492c8f71dac44399988b510f9bf6b074a51 and fixed in 6.3.13 with commit b5b0d52f00e4bacb0ebdf47cd7016b0485fffad2
	Issue introduced in 6.0 with commit 267f2492c8f71dac44399988b510f9bf6b074a51 and fixed in 6.4.4 with commit 10c2b98a40d9044a3e97f4697ca6213bad7e19c2
	Issue introduced in 6.0 with commit 267f2492c8f71dac44399988b510f9bf6b074a51 and fixed in 6.5 with commit 967c28b23f6c89bb8eef6a046ea88afe0d7c1029

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-2023-53777
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/erofs/zdata.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/d3b39ea24835ac03da1a30f93ae7c05d55a40191
	https://git.kernel.org/stable/c/b5b0d52f00e4bacb0ebdf47cd7016b0485fffad2
	https://git.kernel.org/stable/c/10c2b98a40d9044a3e97f4697ca6213bad7e19c2
	https://git.kernel.org/stable/c/967c28b23f6c89bb8eef6a046ea88afe0d7c1029

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