From: Maxim Levitsky Date: Mon, 19 Jul 2021 13:05:00 +0000 (+0300) Subject: KVM: nSVM: always intercept VMLOAD/VMSAVE when nested (CVE-2021-3656) X-Git-Tag: archive/raspbian/5.10.46-5+rpi1^2~27 X-Git-Url: https://dgit.raspbian.org/?a=commitdiff_plain;h=d14addd5932708d4070fc2dea5dc28b865bc23e2;p=linux.git KVM: nSVM: always intercept VMLOAD/VMSAVE when nested (CVE-2021-3656) Origin: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git/commit?id=3dc5666baf2a135f250e4101d41d5959ac2c2e1f Bug-Debian-Security: https://security-tracker.debian.org/tracker/CVE-2021-3656 commit c7dfa4009965a9b2d7b329ee970eb8da0d32f0bc upstream. If L1 disables VMLOAD/VMSAVE intercepts, and doesn't enable Virtual VMLOAD/VMSAVE (currently not supported for the nested hypervisor), then VMLOAD/VMSAVE must operate on the L1 physical memory, which is only possible by making L0 intercept these instructions. Failure to do so allowed the nested guest to run VMLOAD/VMSAVE unintercepted, and thus read/write portions of the host physical memory. Fixes: 89c8a4984fc9 ("KVM: SVM: Enable Virtual VMLOAD VMSAVE feature") Suggested-by: Paolo Bonzini Signed-off-by: Maxim Levitsky Signed-off-by: Paolo Bonzini Signed-off-by: Greg Kroah-Hartman Gbp-Pq: Topic bugfix/x86 Gbp-Pq: Name KVM-nSVM-always-intercept-VMLOAD-VMSAVE-when-nested-.patch --- diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c index 8a229db8530..df17146e841 100644 --- a/arch/x86/kvm/svm/nested.c +++ b/arch/x86/kvm/svm/nested.c @@ -147,6 +147,9 @@ void recalc_intercepts(struct vcpu_svm *svm) for (i = 0; i < MAX_INTERCEPT; i++) c->intercepts[i] |= g->intercepts[i]; + + vmcb_set_intercept(c, INTERCEPT_VMLOAD); + vmcb_set_intercept(c, INTERCEPT_VMSAVE); } static void copy_vmcb_control_area(struct vmcb_control_area *dst,