Commit 13c5183a authored by Marios Pomonis's avatar Marios Pomonis Committed by Paolo Bonzini
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KVM: x86: Protect MSR-based index computations in pmu.h from Spectre-v1/L1TF attacks 



This fixes a Spectre-v1/L1TF vulnerability in the get_gp_pmc() and
get_fixed_pmc() functions.
They both contain index computations based on the (attacker-controlled)
MSR number.

Fixes: 25462f7f ("KVM: x86/vPMU: Define kvm_pmu_ops to support vPMU function dispatch")

Signed-off-by: default avatarNick Finco <nifi@google.com>
Signed-off-by: default avatarMarios Pomonis <pomonis@google.com>
Reviewed-by: default avatarAndrew Honig <ahonig@google.com>
Cc: stable@vger.kernel.org
Reviewed-by: default avatarJim Mattson <jmattson@google.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 25a5edea

arch/x86/kvm/pmu.h

+14 −4
Original line number Diff line number Diff line
@@ -2,6 +2,8 @@ 
#ifndef __KVM_X86_PMU_H

#define __KVM_X86_PMU_H



#include <linux/nospec.h>



#define vcpu_to_pmu(vcpu) (&(vcpu)->arch.pmu)

#define pmu_to_vcpu(pmu)  (container_of((pmu), struct kvm_vcpu, arch.pmu))

#define pmc_to_pmu(pmc)   (&(pmc)->vcpu->arch.pmu)
@@ -102,8 +104,12 @@ static inline bool kvm_valid_perf_global_ctrl(struct kvm_pmu *pmu, 
static inline struct kvm_pmc *get_gp_pmc(struct kvm_pmu *pmu, u32 msr,

					 u32 base)

{

	if (msr >= base && msr < base + pmu->nr_arch_gp_counters)

		return &pmu->gp_counters[msr - base];

	if (msr >= base && msr < base + pmu->nr_arch_gp_counters) {

		u32 index = array_index_nospec(msr - base,

					       pmu->nr_arch_gp_counters);



		return &pmu->gp_counters[index];

	}



	return NULL;

}
@@ -113,8 +119,12 @@ static inline struct kvm_pmc *get_fixed_pmc(struct kvm_pmu *pmu, u32 msr) 
{

	int base = MSR_CORE_PERF_FIXED_CTR0;



	if (msr >= base && msr < base + pmu->nr_arch_fixed_counters)

		return &pmu->fixed_counters[msr - base];

	if (msr >= base && msr < base + pmu->nr_arch_fixed_counters) {

		u32 index = array_index_nospec(msr - base,

					       pmu->nr_arch_fixed_counters);



		return &pmu->fixed_counters[index];

	}



	return NULL;

}