linux-kernel - [PATCH] KVM: x86/pmu: Fix type length error when reading pmu->fixed_ctr

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Date: Tue, 23 Jan 2024 22:12:20 +0000
From: Mingwei Zhang <mizhang@...gle.com>
To: Sean Christopherson <seanjc@...gle.com>, Paolo Bonzini <pbonzini@...hat.com>
Cc: "H. Peter Anvin" <hpa@...or.com>, kvm@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Mingwei Zhang <mizhang@...gle.com>
Subject: [PATCH] KVM: x86/pmu: Fix type length error when reading pmu->fixed_ctr_ctrl

Fix type length error since pmu->fixed_ctr_ctrl is u64 but the local
variable old_fixed_ctr_ctrl is u8. Truncating the value leads to
information loss at runtime. This leads to incorrect value in old_ctrl
retrieved from each field of old_fixed_ctr_ctrl and causes incorrect code
execution within the for loop of reprogram_fixed_counters(). So fix this
type to u64.

Fixes: 76d287b2342e ("KVM: x86/pmu: Drop "u8 ctrl, int idx" for reprogram_fixed_counter()")
Signed-off-by: Mingwei Zhang <mizhang@...gle.com>
---
 arch/x86/kvm/vmx/pmu_intel.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kvm/vmx/pmu_intel.c b/arch/x86/kvm/vmx/pmu_intel.c
index a6216c874729..315c7c2ba89b 100644
--- a/arch/x86/kvm/vmx/pmu_intel.c
+++ b/arch/x86/kvm/vmx/pmu_intel.c
@@ -71,7 +71,7 @@ static int fixed_pmc_events[] = {
 static void reprogram_fixed_counters(struct kvm_pmu *pmu, u64 data)
 {
 	struct kvm_pmc *pmc;
-	u8 old_fixed_ctr_ctrl = pmu->fixed_ctr_ctrl;
+	u64 old_fixed_ctr_ctrl = pmu->fixed_ctr_ctrl;
 	int i;
 
 	pmu->fixed_ctr_ctrl = data;

base-commit: 6613476e225e090cc9aad49be7fa504e290dd33d
-- 
2.43.0.429.g432eaa2c6b-goog