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

Overview

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.

Affected

• Linux >= b2ac58f90540e39324e7a29a7ad471407ae0bf48 < 74836ae4785b9754bb36d0b18fcc1dec4e5e98d2
• Linux >= b2ac58f90540e39324e7a29a7ad471407ae0bf48 < 318ef696fa3c712e46bb62a1a828c3cd62f390c3
• Linux >= b2ac58f90540e39324e7a29a7ad471407ae0bf48 < 55865b3ae03705aa39198783b9cb1f8b96eb44e4
• Linux >= b2ac58f90540e39324e7a29a7ad471407ae0bf48 < 9e06bbb9ade7cdf28d4a3b5b14e5812881c8df85
• Linux f54d0bb8487d2f016fbc4f0e38ef9098f8eb8bd4
• Linux 89be8950bab799ddb9cc3777345e3c21bcb32dba
• Linux >= 3.16.57 < 3.17
• Linux >= 4.4.168 < 4.5
• Linux 4.16

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.