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Date:   Wed, 11 Dec 2019 12:47:53 -0800
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Message-Id: <20191211204753.242298-14-pomonis@google.com>
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Subject: [PATCH v2 13/13] KVM: x86: Protect pmu_intel.c from Spectre-v1/L1TF attacks
From:   Marios Pomonis <pomonis@google.com>
To:     Paolo Bonzini <pbonzini@redhat.com>, rkrcmar@redhat.com,
        Sean Christopherson <sean.j.christopherson@intel.com>,
        Vitaly Kuznetsov <vkuznets@redhat.com>,
        Wanpeng Li <wanpengli@tencent.com>,
        Jim Mattson <jmattson@google.com>,
        Joerg Roedel <joro@8bytes.org>
Cc:     Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        "H. Peter Anvin" <hpa@zytor.com>, x86@kernel.org,
        kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
        Nick Finco <nifi@google.com>, Andrew Honig <ahonig@google.com>,
        Marios Pomonis <pomonis@google.com>, stable@vger.kernel.org
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Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

This fixes Spectre-v1/L1TF vulnerabilities in intel_find_fixed_event()
and intel_rdpmc_ecx_to_pmc().
kvm_rdpmc() (ancestor of intel_find_fixed_event()) and
reprogram_fixed_counter() (ancestor of intel_rdpmc_ecx_to_pmc()) are
exported symbols so KVM should treat them conservatively from a security
perspective.

Fixes: commit 25462f7f5295 ("KVM: x86/vPMU: Define kvm_pmu_ops to support vPMU function dispatch")

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
---
 arch/x86/kvm/vmx/pmu_intel.c | 24 ++++++++++++++++--------
 1 file changed, 16 insertions(+), 8 deletions(-)

diff --git a/arch/x86/kvm/vmx/pmu_intel.c b/arch/x86/kvm/vmx/pmu_intel.c
index 7023138b1cb0..34a3a17bb6d7 100644
--- a/arch/x86/kvm/vmx/pmu_intel.c
+++ b/arch/x86/kvm/vmx/pmu_intel.c
@@ -86,10 +86,14 @@ static unsigned intel_find_arch_event(struct kvm_pmu *pmu,
 
 static unsigned intel_find_fixed_event(int idx)
 {
-	if (idx >= ARRAY_SIZE(fixed_pmc_events))
+	u32 event;
+	size_t size = ARRAY_SIZE(fixed_pmc_events);
+
+	if (idx >= size)
 		return PERF_COUNT_HW_MAX;
 
-	return intel_arch_events[fixed_pmc_events[idx]].event_type;
+	event = fixed_pmc_events[array_index_nospec(idx, size)];
+	return intel_arch_events[event].event_type;
 }
 
 /* check if a PMC is enabled by comparing it with globl_ctrl bits. */
@@ -130,16 +134,20 @@ static struct kvm_pmc *intel_rdpmc_ecx_to_pmc(struct kvm_vcpu *vcpu,
 	struct kvm_pmu *pmu = vcpu_to_pmu(vcpu);
 	bool fixed = idx & (1u << 30);
 	struct kvm_pmc *counters;
+	unsigned int num_counters;
 
 	idx &= ~(3u << 30);
-	if (!fixed && idx >= pmu->nr_arch_gp_counters)
-		return NULL;
-	if (fixed && idx >= pmu->nr_arch_fixed_counters)
+	if (fixed) {
+		counters = pmu->fixed_counters;
+		num_counters = pmu->nr_arch_fixed_counters;
+	} else {
+		counters = pmu->gp_counters;
+		num_counters = pmu->nr_arch_gp_counters;
+	}
+	if (idx >= num_counters)
 		return NULL;
-	counters = fixed ? pmu->fixed_counters : pmu->gp_counters;
 	*mask &= pmu->counter_bitmask[fixed ? KVM_PMC_FIXED : KVM_PMC_GP];
-
-	return &counters[idx];
+	return &counters[array_index_nospec(idx, num_counters)];
 }
 
 static bool intel_is_valid_msr(struct kvm_vcpu *vcpu, u32 msr)
-- 
2.24.0.525.g8f36a354ae-goog