linux-cve-announce - CVE-2025-68293: mm/huge_memory: fix NULL pointer deference when splitting folio

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Message-ID: <2025121640-CVE-2025-68293-ea76@gregkh>
Date: Tue, 16 Dec 2025 16:06:47 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2025-68293: mm/huge_memory: fix NULL pointer deference when splitting folio

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

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

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

mm/huge_memory: fix NULL pointer deference when splitting folio

Commit c010d47f107f ("mm: thp: split huge page to any lower order pages")
introduced an early check on the folio's order via mapping->flags before
proceeding with the split work.

This check introduced a bug: for shmem folios in the swap cache and
truncated folios, the mapping pointer can be NULL.  Accessing
mapping->flags in this state leads directly to a NULL pointer dereference.

This commit fixes the issue by moving the check for mapping != NULL before
any attempt to access mapping->flags.

The Linux kernel CVE team has assigned CVE-2025-68293 to this issue.


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

	Issue introduced in 6.9 with commit c010d47f107f609b9f4d6a103b6dfc53889049e9 and fixed in 6.12.61 with commit 592db83615a9f0164472ec789c2ed34ad35f732f
	Issue introduced in 6.9 with commit c010d47f107f609b9f4d6a103b6dfc53889049e9 and fixed in 6.17.11 with commit d1b83fbacd4397a1d2f8c6b13427a8636ae2b307
	Issue introduced in 6.9 with commit c010d47f107f609b9f4d6a103b6dfc53889049e9 and fixed in 6.18 with commit cff47b9e39a6abf03dde5f4f156f841b0c54bba0

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-2025-68293
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/huge_memory.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/592db83615a9f0164472ec789c2ed34ad35f732f
	https://git.kernel.org/stable/c/d1b83fbacd4397a1d2f8c6b13427a8636ae2b307
	https://git.kernel.org/stable/c/cff47b9e39a6abf03dde5f4f156f841b0c54bba0