CVE-2026-64287: KVM: arm64: Bound used_lrs when flushing the pKVM hyp vCPU

CVE-2026-64287: KVM: arm64: Bound used_lrs when flushing the pKVM hyp vCPU

[Greg Kroah-Hartman]

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

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

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

KVM: arm64: Bound used_lrs when flushing the pKVM hyp vCPU

flush_hyp_vcpu() copies the host vGIC state into the hyp's private vCPU
on every run. The vGIC list register save and restore use used_lrs as
their loop bound and expect it to stay within the number of implemented
list registers. While this is generally the case, flush_hyp_vcpu()
copies vgic_v3 verbatim and does not enforce this, so a value provided
by the host is used at EL2 to index vgic_lr[] and access ICH_LR<n>_EL2
(host -> EL2).

Fix by clamping used_lrs to the number of implemented list registers
after the copy, as the trusted path already does in
vgic_flush_lr_state(). The number of implemented list registers is
constant after init, so it is replicated once from
kvm_vgic_global_state.nr_lr into hyp_gicv3_nr_lr rather than read on
every entry.

The Linux kernel CVE team has assigned CVE-2026-64287 to this issue.


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

	Issue introduced in 6.2 with commit be66e67f175096f283c9d5614c4991fc9e7ed975 and fixed in 6.6.145 with commit 2c5e72b9fbf83fdfa724e9f1af0f418ccf8739b8
	Issue introduced in 6.2 with commit be66e67f175096f283c9d5614c4991fc9e7ed975 and fixed in 6.12.97 with commit 9fa301d8298778dd799fa4dcf7a7f440715d146e
	Issue introduced in 6.2 with commit be66e67f175096f283c9d5614c4991fc9e7ed975 and fixed in 6.18.40 with commit c646431865f4b1a5b14067233fa27b11e05e0d46
	Issue introduced in 6.2 with commit be66e67f175096f283c9d5614c4991fc9e7ed975 and fixed in 7.1.4 with commit 7fca3fcef81c713bc82a37bf741e0f28e6d04a6f
	Issue introduced in 6.2 with commit be66e67f175096f283c9d5614c4991fc9e7ed975 and fixed in 7.2-rc1 with commit 8cc8bbbfab14c22c5551d0dd19b208a44b141c76

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-2026-64287
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/kvm_hyp.h
	arch/arm64/kvm/arm.c
	arch/arm64/kvm/hyp/nvhe/hyp-main.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/2c5e72b9fbf83fdfa724e9f1af0f418ccf8739b8
	https://git.kernel.org/stable/c/9fa301d8298778dd799fa4dcf7a7f440715d146e
	https://git.kernel.org/stable/c/c646431865f4b1a5b14067233fa27b11e05e0d46
	https://git.kernel.org/stable/c/7fca3fcef81c713bc82a37bf741e0f28e6d04a6f
	https://git.kernel.org/stable/c/8cc8bbbfab14c22c5551d0dd19b208a44b141c76