linux-cve-announce - CVE-2022-49744: mm/uffd: fix pte marker when fork() without fork event

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Message-ID: <2025032758-CVE-2022-49744-8c5a@gregkh>
Date: Thu, 27 Mar 2025 17:43:02 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: CVE-2022-49744: mm/uffd: fix pte marker when fork() without fork event

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

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

mm/uffd: fix pte marker when fork() without fork event

Patch series "mm: Fixes on pte markers".

Patch 1 resolves the syzkiller report from Pengfei.

Patch 2 further harden pte markers when used with the recent swapin error
markers.  The major case is we should persist a swapin error marker after
fork(), so child shouldn't read a corrupted page.

This patch (of 2):

When fork(), dst_vma is not guaranteed to have VM_UFFD_WP even if src may
have it and has pte marker installed.  The warning is improper along with
the comment.  The right thing is to inherit the pte marker when needed, or
keep the dst pte empty.

A vague guess is this happened by an accident when there's the prior patch
to introduce src/dst vma into this helper during the uffd-wp feature got
developed and I probably messed up in the rebase, since if we replace
dst_vma with src_vma the warning & comment it all makes sense too.

Hugetlb did exactly the right here (copy_hugetlb_page_range()).  Fix the
general path.

Reproducer:

https://github.com/xupengfe/syzkaller_logs/blob/main/221208_115556_copy_page_range/repro.c

Bugzilla report: https://bugzilla.kernel.org/show_bug.cgi?id=216808

The Linux kernel CVE team has assigned CVE-2022-49744 to this issue.

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

	Issue introduced in 5.19 with commit c56d1b62cce83695823c13e52f73e92eb568c0c1 and fixed in 6.1.11 with commit 2d11727655bf931776fb541f5862daf04bd5bf02
	Issue introduced in 5.19 with commit c56d1b62cce83695823c13e52f73e92eb568c0c1 and fixed in 6.2 with commit 49d6d7fb631345b0f2957a7c4be24ad63903150f

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-2022-49744
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/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/2d11727655bf931776fb541f5862daf04bd5bf02
	https://git.kernel.org/stable/c/49d6d7fb631345b0f2957a7c4be24ad63903150f