linux-cve-announce - CVE-2022-49181: xen: fix is_xen

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Message-ID: <2025022614-CVE-2022-49181-8181@gregkh>
Date: Wed, 26 Feb 2025 02:56:26 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: CVE-2022-49181: xen: fix is_xen_pmu()

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

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

xen: fix is_xen_pmu()

is_xen_pmu() is taking the cpu number as parameter, but it is not using
it. Instead it just tests whether the Xen PMU initialization on the
current cpu did succeed. As this test is done by checking a percpu
pointer, preemption needs to be disabled in order to avoid switching
the cpu while doing the test. While resuming from suspend() this seems
not to be the case:

[   88.082751] ACPI: PM: Low-level resume complete
[   88.087933] ACPI: EC: EC started
[   88.091464] ACPI: PM: Restoring platform NVS memory
[   88.097166] xen_acpi_processor: Uploading Xen processor PM info
[   88.103850] Enabling non-boot CPUs ...
[   88.108128] installing Xen timer for CPU 1
[   88.112763] BUG: using smp_processor_id() in preemptible [00000000] code: systemd-sleep/7138
[   88.122256] caller is is_xen_pmu+0x12/0x30
[   88.126937] CPU: 0 PID: 7138 Comm: systemd-sleep Tainted: G        W         5.16.13-2.fc32.qubes.x86_64 #1
[   88.137939] Hardware name: Star Labs StarBook/StarBook, BIOS 7.97 03/21/2022
[   88.145930] Call Trace:
[   88.148757]  <TASK>
[   88.151193]  dump_stack_lvl+0x48/0x5e
[   88.155381]  check_preemption_disabled+0xde/0xe0
[   88.160641]  is_xen_pmu+0x12/0x30
[   88.164441]  xen_smp_intr_init_pv+0x75/0x100

Fix that by replacing is_xen_pmu() by a simple boolean variable which
reflects the Xen PMU initialization state on cpu 0.

Modify xen_pmu_init() to return early in case it is being called for a
cpu other than cpu 0 and the boolean variable not being set.

The Linux kernel CVE team has assigned CVE-2022-49181 to this issue.


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

	Issue introduced in 4.3 with commit bf6dfb154d935725c9a2005033ca33017b9df439 and fixed in 4.14.276 with commit e9f72105cf4a16bb185093b60fc12dbc82fe15b5
	Issue introduced in 4.3 with commit bf6dfb154d935725c9a2005033ca33017b9df439 and fixed in 4.19.238 with commit d533c4a2e8c4ca3a0fe84d295a7bd43af1931028
	Issue introduced in 4.3 with commit bf6dfb154d935725c9a2005033ca33017b9df439 and fixed in 5.4.189 with commit ab2c789d1c0a3d0a682f7aa287754193471ff9f8
	Issue introduced in 4.3 with commit bf6dfb154d935725c9a2005033ca33017b9df439 and fixed in 5.10.110 with commit e9445a7a59d84ed3ae6c85f299d2a6c4930b1ee9
	Issue introduced in 4.3 with commit bf6dfb154d935725c9a2005033ca33017b9df439 and fixed in 5.15.33 with commit af884b276b08e2b7e74c2b9208df35f36fa6a54c
	Issue introduced in 4.3 with commit bf6dfb154d935725c9a2005033ca33017b9df439 and fixed in 5.16.19 with commit 980bc42812c0a4788aee4b519bc911bfb911c23c
	Issue introduced in 4.3 with commit bf6dfb154d935725c9a2005033ca33017b9df439 and fixed in 5.17.2 with commit 26911a822148bef5dcfc55e7df49cb05a18737e3
	Issue introduced in 4.3 with commit bf6dfb154d935725c9a2005033ca33017b9df439 and fixed in 5.18 with commit de2ae403b4c0e79a3410e63bc448542fbb9f9bfc

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-2022-49181
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/x86/xen/pmu.c
	arch/x86/xen/pmu.h
	arch/x86/xen/smp_pv.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/e9f72105cf4a16bb185093b60fc12dbc82fe15b5
	https://git.kernel.org/stable/c/d533c4a2e8c4ca3a0fe84d295a7bd43af1931028
	https://git.kernel.org/stable/c/ab2c789d1c0a3d0a682f7aa287754193471ff9f8
	https://git.kernel.org/stable/c/e9445a7a59d84ed3ae6c85f299d2a6c4930b1ee9
	https://git.kernel.org/stable/c/af884b276b08e2b7e74c2b9208df35f36fa6a54c
	https://git.kernel.org/stable/c/980bc42812c0a4788aee4b519bc911bfb911c23c
	https://git.kernel.org/stable/c/26911a822148bef5dcfc55e7df49cb05a18737e3
	https://git.kernel.org/stable/c/de2ae403b4c0e79a3410e63bc448542fbb9f9bfc