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[2/8] KVM: arm64: PSCI: Narrow input registers when using 32bit functions

Message ID 20200423154009.4113562-3-maz@kernel.org (mailing list archive)
State New, archived
Headers show
Series [GIT,PULL] KVM/arm fixes for 5.7, take #1 | expand

Commit Message

Marc Zyngier April 23, 2020, 3:40 p.m. UTC 
When a guest delibarately uses an SMC32 function number (which is allowed),
we should make sure we drop the top 32bits from the input arguments, as they
could legitimately be junk.

Reported-by: Christoffer Dall <christoffer.dall@arm.com>
Reviewed-by: Christoffer Dall <christoffer.dall@arm.com>
Reviewed-by: Alexandru Elisei <alexandru.elisei@arm.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
---
 virt/kvm/arm/psci.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)
diff mbox series

Patch

diff --git a/virt/kvm/arm/psci.c b/virt/kvm/arm/psci.c
index 14a162e295a94..3772717efe3e5 100644
--- a/virt/kvm/arm/psci.c
+++ b/virt/kvm/arm/psci.c
@@ -186,6 +186,18 @@  static void kvm_psci_system_reset(struct kvm_vcpu *vcpu)
 	kvm_prepare_system_event(vcpu, KVM_SYSTEM_EVENT_RESET);
 }
 
+static void kvm_psci_narrow_to_32bit(struct kvm_vcpu *vcpu)
+{
+	int i;
+
+	/*
+	 * Zero the input registers' upper 32 bits. They will be fully
+	 * zeroed on exit, so we're fine changing them in place.
+	 */
+	for (i = 1; i < 4; i++)
+		vcpu_set_reg(vcpu, i, lower_32_bits(vcpu_get_reg(vcpu, i)));
+}
+
 static int kvm_psci_0_2_call(struct kvm_vcpu *vcpu)
 {
 	struct kvm *kvm = vcpu->kvm;
@@ -210,12 +222,16 @@  static int kvm_psci_0_2_call(struct kvm_vcpu *vcpu)
 		val = PSCI_RET_SUCCESS;
 		break;
 	case PSCI_0_2_FN_CPU_ON:
+		kvm_psci_narrow_to_32bit(vcpu);
+		fallthrough;
 	case PSCI_0_2_FN64_CPU_ON:
 		mutex_lock(&kvm->lock);
 		val = kvm_psci_vcpu_on(vcpu);
 		mutex_unlock(&kvm->lock);
 		break;
 	case PSCI_0_2_FN_AFFINITY_INFO:
+		kvm_psci_narrow_to_32bit(vcpu);
+		fallthrough;
 	case PSCI_0_2_FN64_AFFINITY_INFO:
 		val = kvm_psci_vcpu_affinity_info(vcpu);
 		break;