Commit ea740059 authored Dec 11, 2019 by Marios Pomonis Committed by Paolo Bonzini Jan 27, 2020

KVM: x86: Protect DR-based index computations from Spectre-v1/L1TF attacks



This fixes a Spectre-v1/L1TF vulnerability in __kvm_set_dr() and
kvm_get_dr().
Both kvm_get_dr() and kvm_set_dr() (a wrapper of __kvm_set_dr()) are
exported symbols so KVM should tream them conservatively from a security
perspective.

Fixes: 020df079 ("KVM: move DR register access handling into generic code")

Signed-off-by: Nick Finco <nifi@google.com>
Signed-off-by: Marios Pomonis <pomonis@google.com>
Reviewed-by: Andrew Honig <ahonig@google.com>
Cc: stable@vger.kernel.org
Reviewed-by: Jim Mattson <jmattson@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

parent c926f2f7

arch/x86/kvm/x86.c

+6 −2

Original line number	Diff line number	Diff line
		@@ -1063,9 +1063,11 @@ static u64 kvm_dr6_fixed(struct kvm_vcpu *vcpu)

		static int __kvm_set_dr(struct kvm_vcpu *vcpu, int dr, unsigned long val)
		{
		size_t size = ARRAY_SIZE(vcpu->arch.db);

		switch (dr) {
		case 0 ... 3:
		vcpu->arch.db[dr] = val;
		vcpu->arch.db[array_index_nospec(dr, size)] = val;
		if (!(vcpu->guest_debug & KVM_GUESTDBG_USE_HW_BP))
		vcpu->arch.eff_db[dr] = val;
		break;
		@@ -1102,9 +1104,11 @@ EXPORT_SYMBOL_GPL(kvm_set_dr);

		int kvm_get_dr(struct kvm_vcpu vcpu, int dr, unsigned long val)
		{
		size_t size = ARRAY_SIZE(vcpu->arch.db);

		switch (dr) {
		case 0 ... 3:
		*val = vcpu->arch.db[dr];
		*val = vcpu->arch.db[array_index_nospec(dr, size)];
		break;
		case 4:
		/* fall through */

Admin message