linux-cve-announce - CVE-2025-38692: exfat: add cluster chain loop check for dir

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Message-ID: <2025090450-CVE-2025-38692-90f5@gregkh>
Date: Thu,  4 Sep 2025 17:32:57 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2025-38692: exfat: add cluster chain loop check for dir

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

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

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

exfat: add cluster chain loop check for dir

An infinite loop may occur if the following conditions occur due to
file system corruption.

(1) Condition for exfat_count_dir_entries() to loop infinitely.
    - The cluster chain includes a loop.
    - There is no UNUSED entry in the cluster chain.

(2) Condition for exfat_create_upcase_table() to loop infinitely.
    - The cluster chain of the root directory includes a loop.
    - There are no UNUSED entry and up-case table entry in the cluster
      chain of the root directory.

(3) Condition for exfat_load_bitmap() to loop infinitely.
    - The cluster chain of the root directory includes a loop.
    - There are no UNUSED entry and bitmap entry in the cluster chain
      of the root directory.

(4) Condition for exfat_find_dir_entry() to loop infinitely.
    - The cluster chain includes a loop.
    - The unused directory entries were exhausted by some operation.

(5) Condition for exfat_check_dir_empty() to loop infinitely.
    - The cluster chain includes a loop.
    - The unused directory entries were exhausted by some operation.
    - All files and sub-directories under the directory are deleted.

This commit adds checks to break the above infinite loop.

The Linux kernel CVE team has assigned CVE-2025-38692 to this issue.


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

	Fixed in 6.6.103 with commit 868f23286c1a13162330fa6c614fe350f78e3f82
	Fixed in 6.12.43 with commit aa8fe7b7b73d4c9a41bb96cb3fb3092f794ecb33
	Fixed in 6.15.11 with commit e2066ca3ef49a30920d8536fa366b2a183a808ee
	Fixed in 6.16.2 with commit 4c3cda20c4cf1871e27868d08fda06b79bc7d568
	Fixed in 6.17-rc1 with commit 99f9a97dce39ad413c39b92c90393bbd6778f3fd

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-2025-38692
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/exfat/dir.c
	fs/exfat/fatent.c
	fs/exfat/namei.c
	fs/exfat/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/868f23286c1a13162330fa6c614fe350f78e3f82
	https://git.kernel.org/stable/c/aa8fe7b7b73d4c9a41bb96cb3fb3092f794ecb33
	https://git.kernel.org/stable/c/e2066ca3ef49a30920d8536fa366b2a183a808ee
	https://git.kernel.org/stable/c/4c3cda20c4cf1871e27868d08fda06b79bc7d568
	https://git.kernel.org/stable/c/99f9a97dce39ad413c39b92c90393bbd6778f3fd