CVE-2026-98716: KVM: SVM: Use the active VMCB's MSR bitmap when checking if MSR is intercepted

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

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

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

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

KVM: SVM: Use the active VMCB's MSR bitmap when checking if MSR is intercepted

Use the MSR permission bitmap of the active VMCB instead of assuming that
KVM is always using vmcb02's bitmap when L2 is active, as KVM uses msrpm02
if and only if L1 wants to intercept MSR accesses, i.e. if and only if KVM
needs to merge msprm01 with msrpm12.

Don't bother tracking the virtual address of the bitmap that's being used,
as __va() is cheap on x86, and caching the virtual address would introduce
yet another source of potentially stale information.

The Linux kernel CVE team has assigned CVE-2026-98716 to this issue.


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

	Issue introduced in 4.16 with commit b2ac58f90540e39324e7a29a7ad471407ae0bf48 and fixed in 6.12.113 with commit 74836ae4785b9754bb36d0b18fcc1dec4e5e98d2
	Issue introduced in 4.16 with commit b2ac58f90540e39324e7a29a7ad471407ae0bf48 and fixed in 6.18.56 with commit 318ef696fa3c712e46bb62a1a828c3cd62f390c3
	Issue introduced in 4.16 with commit b2ac58f90540e39324e7a29a7ad471407ae0bf48 and fixed in 7.2.10 with commit 55865b3ae03705aa39198783b9cb1f8b96eb44e4
	Issue introduced in 4.16 with commit b2ac58f90540e39324e7a29a7ad471407ae0bf48 and fixed in 7.3-rc6 with commit 9e06bbb9ade7cdf28d4a3b5b14e5812881c8df85
	Issue introduced in 3.16.57 with commit f54d0bb8487d2f016fbc4f0e38ef9098f8eb8bd4
	Issue introduced in 4.4.168 with commit 89be8950bab799ddb9cc3777345e3c21bcb32dba

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-2026-98716
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/svm/svm.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/74836ae4785b9754bb36d0b18fcc1dec4e5e98d2
	https://git.kernel.org/stable/c/318ef696fa3c712e46bb62a1a828c3cd62f390c3
	https://git.kernel.org/stable/c/55865b3ae03705aa39198783b9cb1f8b96eb44e4
	https://git.kernel.org/stable/c/9e06bbb9ade7cdf28d4a3b5b14e5812881c8df85