CVE-2026-64562: KVM: nVMX: Hide shadow VMCS right after VMCLEAR

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

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

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

KVM: nVMX: Hide shadow VMCS right after VMCLEAR

free_nested() frees the shadow VMCS while vmcs01 still points to it. But
because it is asynchronous with respect to loaded_vmcs_clear(), the vCPU
might migrate before the pointer is cleared and __loaded_vmcs_clear()
may then execute VMCLEAR.

The VMCS needs to stay attached until its explicit VMCLEAR completes, but
then it can be hidden and the page safely freed.

The Linux kernel CVE team has assigned CVE-2026-64562 to this issue.


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

	Issue introduced in 4.9 with commit 355f4fb1405ec29d0fac49b4d41fcd78cbd455d5 and fixed in 6.6.148 with commit af56298e9d86e6098cd1d2e155cb2949b7c45412
	Issue introduced in 4.9 with commit 355f4fb1405ec29d0fac49b4d41fcd78cbd455d5 and fixed in 6.12.101 with commit 589419470030a89f16cf19300658b6dc644ca946
	Issue introduced in 4.9 with commit 355f4fb1405ec29d0fac49b4d41fcd78cbd455d5 and fixed in 6.18.42 with commit 8001d2ce9d9bd09118ce523aef595aa094573ae3
	Issue introduced in 4.9 with commit 355f4fb1405ec29d0fac49b4d41fcd78cbd455d5 and fixed in 7.1.6 with commit 1dabef6e206568bf9d9ade74f6e56a48ea35695d
	Issue introduced in 4.9 with commit 355f4fb1405ec29d0fac49b4d41fcd78cbd455d5 and fixed in 7.2-rc5 with commit 622ebfac01ba4f9c0060cebd41257fe46fc4a0b3

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-2026-64562
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/kvm/vmx/nested.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/af56298e9d86e6098cd1d2e155cb2949b7c45412
	https://git.kernel.org/stable/c/589419470030a89f16cf19300658b6dc644ca946
	https://git.kernel.org/stable/c/8001d2ce9d9bd09118ce523aef595aa094573ae3
	https://git.kernel.org/stable/c/1dabef6e206568bf9d9ade74f6e56a48ea35695d
	https://git.kernel.org/stable/c/622ebfac01ba4f9c0060cebd41257fe46fc4a0b3