Subject: CVE-2023-52740: powerpc/64s/interrupt: Fix interrupt exit race with security mitigation switch

From: Greg Kroah-Hartman <[email-masked]>

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

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

powerpc/64s/interrupt: Fix interrupt exit race with security mitigation switch

The RFI and STF security mitigation options can flip the
interrupt_exit_not_reentrant static branch condition concurrently with
the interrupt exit code which tests that branch.

Interrupt exit tests this condition to set MSR[EE|RI] for exit, then
again in the case a soft-masked interrupt is found pending, to recover
the MSR so the interrupt can be replayed before attempting to exit
again. If the condition changes between these two tests, the MSR and irq
soft-mask state will become corrupted, leading to warnings and possible
crashes. For example, if the branch is initially true then false,
MSR[EE] will be 0 but PACA_IRQ_HARD_DIS clear and EE may not get
enabled, leading to warnings in irq_64.c.

The Linux kernel CVE team has assigned CVE-2023-52740 to this issue.

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

	Issue introduced in 5.14 with commit 13799748b957 and fixed in 5.15.94 with commit 86f7e4239336
	Issue introduced in 5.14 with commit 13799748b957 and fixed in 6.1.12 with commit 6f097c24815e
	Issue introduced in 5.14 with commit 13799748b957 and fixed in 6.2 with commit 2ea31e2e62bb

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-2023-52740
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/powerpc/kernel/interrupt.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/86f7e423933608d536015a0f2eb9e0338c1227e0
	https://git.kernel.org/stable/c/6f097c24815e67909a1fcc2c605586d02babd673
	https://git.kernel.org/stable/c/2ea31e2e62bbc4d11c411eeb36f1b02841dbcab1