linux-cve-announce - CVE-2025-68292: mm/memfd: fix information leak in hugetlb folios

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Message-ID: <2025121640-CVE-2025-68292-434b@gregkh>
Date: Tue, 16 Dec 2025 16:06:46 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2025-68292: mm/memfd: fix information leak in hugetlb folios

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

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

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

mm/memfd: fix information leak in hugetlb folios

When allocating hugetlb folios for memfd, three initialization steps are
missing:

1. Folios are not zeroed, leading to kernel memory disclosure to userspace
2. Folios are not marked uptodate before adding to page cache
3. hugetlb_fault_mutex is not taken before hugetlb_add_to_page_cache()

The memfd allocation path bypasses the normal page fault handler
(hugetlb_no_page) which would handle all of these initialization steps. 
This is problematic especially for udmabuf use cases where folios are
pinned and directly accessed by userspace via DMA.

Fix by matching the initialization pattern used in hugetlb_no_page():
- Zero the folio using folio_zero_user() which is optimized for huge pages
- Mark it uptodate with folio_mark_uptodate()
- Take hugetlb_fault_mutex before adding to page cache to prevent races

The folio_zero_user() change also fixes a potential security issue where
uninitialized kernel memory could be disclosed to userspace through read()
or mmap() operations on the memfd.

The Linux kernel CVE team has assigned CVE-2025-68292 to this issue.


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

	Issue introduced in 6.11 with commit 89c1905d9c140372b7f50ef48f42378cf85d9bc5 and fixed in 6.12.61 with commit 50b4c1c28733a536d637d2f0401d60bcfef60ef2
	Issue introduced in 6.11 with commit 89c1905d9c140372b7f50ef48f42378cf85d9bc5 and fixed in 6.17.11 with commit b09d7c4dc642849d9a96753233c6d00364017fd6
	Issue introduced in 6.11 with commit 89c1905d9c140372b7f50ef48f42378cf85d9bc5 and fixed in 6.18 with commit de8798965fd0d9a6c47fc2ac57767ec32de12b49

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-2025-68292
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/memfd.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/50b4c1c28733a536d637d2f0401d60bcfef60ef2
	https://git.kernel.org/stable/c/b09d7c4dc642849d9a96753233c6d00364017fd6
	https://git.kernel.org/stable/c/de8798965fd0d9a6c47fc2ac57767ec32de12b49