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Commit 6c7a5dce authored by Andrew Jones's avatar Andrew Jones Committed by Christoffer Dall
Browse files

KVM: arm/arm64: fix races in kvm_psci_vcpu_on 



Fix potential races in kvm_psci_vcpu_on() by taking the kvm->lock
mutex.  In general, it's a bad idea to allow more than one PSCI_CPU_ON
to process the same target VCPU at the same time.  One such problem
that may arise is that one PSCI_CPU_ON could be resetting the target
vcpu, which fills the entire sys_regs array with a temporary value
including the MPIDR register, while another looks up the VCPU based
on the MPIDR value, resulting in no target VCPU found.  Resolves both
races found with the kvm-unit-tests/arm/psci unit test.

Reviewed-by: default avatarMarc Zyngier <marc.zyngier@arm.com>
Reviewed-by: default avatarChristoffer Dall <cdall@linaro.org>
Reported-by: default avatarLevente Kurusa <lkurusa@redhat.com>
Suggested-by: default avatarChristoffer Dall <cdall@linaro.org>
Signed-off-by: default avatarAndrew Jones <drjones@redhat.com>
Cc: stable@vger.kernel.org
Signed-off-by: default avatarChristoffer Dall <cdall@linaro.org>
parent 5f6e0070

arch/arm/kvm/psci.c

+7 −1
Original line number Diff line number Diff line
@@ -208,9 +208,10 @@ int kvm_psci_version(struct kvm_vcpu *vcpu) 


static int kvm_psci_0_2_call(struct kvm_vcpu *vcpu)

{

	int ret = 1;

	struct kvm *kvm = vcpu->kvm;

	unsigned long psci_fn = vcpu_get_reg(vcpu, 0) & ~((u32) 0);

	unsigned long val;

	int ret = 1;



	switch (psci_fn) {

	case PSCI_0_2_FN_PSCI_VERSION:
@@ -230,7 +231,9 @@ static int kvm_psci_0_2_call(struct kvm_vcpu *vcpu) 
		break;

	case PSCI_0_2_FN_CPU_ON:

	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:

	case PSCI_0_2_FN64_AFFINITY_INFO:
@@ -279,6 +282,7 @@ static int kvm_psci_0_2_call(struct kvm_vcpu *vcpu) 


static int kvm_psci_0_1_call(struct kvm_vcpu *vcpu)

{

	struct kvm *kvm = vcpu->kvm;

	unsigned long psci_fn = vcpu_get_reg(vcpu, 0) & ~((u32) 0);

	unsigned long val;
@@ -288,7 +292,9 @@ static int kvm_psci_0_1_call(struct kvm_vcpu *vcpu) 
		val = PSCI_RET_SUCCESS;

		break;

	case KVM_PSCI_FN_CPU_ON:

		mutex_lock(&kvm->lock);

		val = kvm_psci_vcpu_on(vcpu);

		mutex_unlock(&kvm->lock);

		break;

	default:

		val = PSCI_RET_NOT_SUPPORTED;