linux-cve-announce - CVE-2025-38058: __legitimize_mnt(): check for MNT_SYNC_UMOUNT should be under mount

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Message-ID: <2025061834-CVE-2025-38058-fe06@gregkh>
Date: Wed, 18 Jun 2025 11:33:53 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2025-38058: __legitimize_mnt(): check for MNT_SYNC_UMOUNT should be under mount_lock

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

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

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

__legitimize_mnt(): check for MNT_SYNC_UMOUNT should be under mount_lock

... or we risk stealing final mntput from sync umount - raising mnt_count
after umount(2) has verified that victim is not busy, but before it
has set MNT_SYNC_UMOUNT; in that case __legitimize_mnt() doesn't see
that it's safe to quietly undo mnt_count increment and leaves dropping
the reference to caller, where it'll be a full-blown mntput().

Check under mount_lock is needed; leaving the current one done before
taking that makes no sense - it's nowhere near common enough to bother
with.

The Linux kernel CVE team has assigned CVE-2025-38058 to this issue.


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

	Fixed in 5.4.294 with commit 628fb00195ce21a90cf9e4e3d105cd9e58f77b40
	Fixed in 5.10.238 with commit b89eb56a378b7b2c1176787fc228d0a57172bdd5
	Fixed in 5.15.185 with commit f6d45fd92f62845cbd1eb5128fd8f0ed7d0c5a42
	Fixed in 6.1.141 with commit 9b0915e72b3cf52474dcee0b24a2f99d93e604a3
	Fixed in 6.6.93 with commit d8ece4ced3b051e656c77180df2e69e19e24edc1
	Fixed in 6.12.31 with commit 8cafd7266fa02e0863bacbf872fe635c0b9725eb
	Fixed in 6.14.9 with commit b55996939c71a3e1a38f3cdc6a8859797efc9083
	Fixed in 6.15 with commit 250cf3693060a5f803c5f1ddc082bb06b16112a9

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-2025-38058
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/namespace.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/628fb00195ce21a90cf9e4e3d105cd9e58f77b40
	https://git.kernel.org/stable/c/b89eb56a378b7b2c1176787fc228d0a57172bdd5
	https://git.kernel.org/stable/c/f6d45fd92f62845cbd1eb5128fd8f0ed7d0c5a42
	https://git.kernel.org/stable/c/9b0915e72b3cf52474dcee0b24a2f99d93e604a3
	https://git.kernel.org/stable/c/d8ece4ced3b051e656c77180df2e69e19e24edc1
	https://git.kernel.org/stable/c/8cafd7266fa02e0863bacbf872fe635c0b9725eb
	https://git.kernel.org/stable/c/b55996939c71a3e1a38f3cdc6a8859797efc9083
	https://git.kernel.org/stable/c/250cf3693060a5f803c5f1ddc082bb06b16112a9