KVM: nSVM: avoid picking up unsupported bits from L2 in int_ctl (CVE-2021-3653)

KVM: nSVM: avoid picking up unsupported bits from L2 in int_ctl (CVE-2021-3653)

Origin: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git/commit?id=c0883f693187c646c0972d73e525523f9486c2e3
Bug-Debian-Security: https://security-tracker.debian.org/tracker/CVE-2021-3653

commit 0f923e07124df069ba68d8bb12324398f4b6b709 upstream.

* Invert the mask of bits that we pick from L2 in
  nested_vmcb02_prepare_control

* Invert and explicitly use VIRQ related bits bitmask in svm_clear_vintr

This fixes a security issue that allowed a malicious L1 to run L2 with
AVIC enabled, which allowed the L2 to exploit the uninitialized and enabled
AVIC to read/write the host physical memory at some offsets.

Fixes: 3d6368ef580a ("KVM: SVM: Add VMRUN handler")
Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Gbp-Pq: Topic bugfix/x86
Gbp-Pq: Name KVM-nSVM-avoid-picking-up-unsupported-bits-from-L2-i.patch