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KVM: arm/arm64: fix races in kvm_psci_vcpu_on

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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: Marc Zyngier <marc.zyngier@arm.com>
Reviewed-by: Christoffer Dall <cdall@linaro.org>
Reported-by: Levente Kurusa <lkurusa@redhat.com>
Suggested-by: Christoffer Dall <cdall@linaro.org>
Signed-off-by: Andrew Jones <drjones@redhat.com>
Cc: stable@vger.kernel.org
Signed-off-by: Christoffer Dall <cdall@linaro.org>
This commit is contained in:
Andrew Jones 2017-04-18 17:59:58 +02:00 committed by Christoffer Dall
parent 5f6e00709c
commit 6c7a5dce22
1 changed files with 7 additions and 1 deletions
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8
arch/arm/kvm/psci.c
View file

@ -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;