linux-cve-announce - CVE-2022-50230: arm64: set UXN on swapper page tables

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Message-ID: <2025061850-CVE-2022-50230-034a@gregkh>
Date: Wed, 18 Jun 2025 13:04:55 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2022-50230: arm64: set UXN on swapper page tables

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

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

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

arm64: set UXN on swapper page tables

[ This issue was fixed upstream by accident in c3cee924bd85 ("arm64:
  head: cover entire kernel image in initial ID map") as part of a
  large refactoring of the arm64 boot flow. This simple fix is therefore
  preferred for -stable backporting ]

On a system that implements FEAT_EPAN, read/write access to the idmap
is denied because UXN is not set on the swapper PTEs. As a result,
idmap_kpti_install_ng_mappings panics the kernel when accessing
__idmap_kpti_flag. Fix it by setting UXN on these PTEs.

The Linux kernel CVE team has assigned CVE-2022-50230 to this issue.

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

	Issue introduced in 5.13 with commit 18107f8a2df6bf1c6cac8d0713f757f866d5af51 and fixed in 5.19.1 with commit 9283e708a9b8529e7aafac9ab5c5c79a9fab8846

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-2022-50230
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/arm64/include/asm/kernel-pgtable.h
	arch/arm64/kernel/head.S

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/9283e708a9b8529e7aafac9ab5c5c79a9fab8846