linux-cve-announce - CVE-2025-40174: x86/mm: Fix SMP ordering in switch_mm_irqs

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Message-ID: <2025111255-CVE-2025-40174-b076@gregkh>
Date: Wed, 12 Nov 2025 05:53:57 -0500
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2025-40174: x86/mm: Fix SMP ordering in switch_mm_irqs_off()

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

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

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

x86/mm: Fix SMP ordering in switch_mm_irqs_off()

Stephen noted that it is possible to not have an smp_mb() between
the loaded_mm store and the tlb_gen load in switch_mm(), meaning the
ordering against flush_tlb_mm_range() goes out the window, and it
becomes possible for switch_mm() to not observe a recent tlb_gen
update and fail to flush the TLBs.

[ dhansen: merge conflict fixed by Ingo ]

The Linux kernel CVE team has assigned CVE-2025-40174 to this issue.


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

	Issue introduced in 6.14 with commit 209954cbc7d0ce1a190fc725d20ce303d74d2680 and fixed in 6.17.5 with commit 0fe5e3f5fb75c5d88dad24dece3ee75e9d87adeb
	Issue introduced in 6.14 with commit 209954cbc7d0ce1a190fc725d20ce303d74d2680 and fixed in 6.18-rc2 with commit 83b0177a6c4889b3a6e865da5e21b2c9d97d0551

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-2025-40174
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:
	arch/x86/mm/tlb.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/0fe5e3f5fb75c5d88dad24dece3ee75e9d87adeb
	https://git.kernel.org/stable/c/83b0177a6c4889b3a6e865da5e21b2c9d97d0551