linux-cve-announce - CVE-2025-40218: mm/damon/vaddr: do not repeat pte_offset_map

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Message-ID: <2025120452-CVE-2025-40218-d4dc@gregkh>
Date: Thu,  4 Dec 2025 15:50:52 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2025-40218: mm/damon/vaddr: do not repeat pte_offset_map_lock() until success

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

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

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

mm/damon/vaddr: do not repeat pte_offset_map_lock() until success

DAMON's virtual address space operation set implementation (vaddr) calls
pte_offset_map_lock() inside the page table walk callback function.  This
is for reading and writing page table accessed bits.  If
pte_offset_map_lock() fails, it retries by returning the page table walk
callback function with ACTION_AGAIN.

pte_offset_map_lock() can continuously fail if the target is a pmd
migration entry, though.  Hence it could cause an infinite page table walk
if the migration cannot be done until the page table walk is finished. 
This indeed caused a soft lockup when CPU hotplugging and DAMON were
running in parallel.

Avoid the infinite loop by simply not retrying the page table walk.  DAMON
is promising only a best-effort accuracy, so missing access to such pages
is no problem.

The Linux kernel CVE team has assigned CVE-2025-40218 to this issue.

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

	Issue introduced in 6.5 with commit 7780d04046a2288ab85d88bedacc60fa4fad9971 and fixed in 6.6.113 with commit 677ebfe5d00f94adec0c0204f6e6e2a82d3f77bf
	Issue introduced in 6.5 with commit 7780d04046a2288ab85d88bedacc60fa4fad9971 and fixed in 6.12.54 with commit ac42320ec873bfe726141069cfdd90ee5bc4e885
	Issue introduced in 6.5 with commit 7780d04046a2288ab85d88bedacc60fa4fad9971 and fixed in 6.17.4 with commit 0ccd91cf749536d41307a07e60ec14ab0dbf21f5
	Issue introduced in 6.5 with commit 7780d04046a2288ab85d88bedacc60fa4fad9971 and fixed in 6.18 with commit b93af2cc8e036754c0d9970d9ddc47f43cc94b9f

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-2025-40218
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:
	mm/damon/vaddr.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/677ebfe5d00f94adec0c0204f6e6e2a82d3f77bf
	https://git.kernel.org/stable/c/ac42320ec873bfe726141069cfdd90ee5bc4e885
	https://git.kernel.org/stable/c/0ccd91cf749536d41307a07e60ec14ab0dbf21f5
	https://git.kernel.org/stable/c/b93af2cc8e036754c0d9970d9ddc47f43cc94b9f