linux-kernel - [PATCH 5.15 205/279] KVM: x86: Fix uninitialized eoi_exit_bitmap usage in vcpu_load_eoi

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Date:   Wed, 24 Nov 2021 12:58:12 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Vitaly Kuznetsov <vkuznets@...hat.com>,
        Huang Le <huangle1@...com>, Paolo Bonzini <pbonzini@...hat.com>
Subject: [PATCH 5.15 205/279] KVM: x86: Fix uninitialized eoi_exit_bitmap usage in vcpu_load_eoi_exitmap()

From: 黄乐 <huangle1@...com>

commit c5adbb3af051079f35abfa26551107e2c653087f upstream.

In vcpu_load_eoi_exitmap(), currently the eoi_exit_bitmap[4] array is
initialized only when Hyper-V context is available, in other path it is
just passed to kvm_x86_ops.load_eoi_exitmap() directly from on the stack,
which would cause unexpected interrupt delivery/handling issues, e.g. an
*old* linux kernel that relies on PIT to do clock calibration on KVM might
randomly fail to boot.

Fix it by passing ioapic_handled_vectors to load_eoi_exitmap() when Hyper-V
context is not available.

Fixes: f2bc14b69c38 ("KVM: x86: hyper-v: Prepare to meet unallocated Hyper-V context")
Cc: stable@...r.kernel.org
Reviewed-by: Vitaly Kuznetsov <vkuznets@...hat.com>
Signed-off-by: Huang Le <huangle1@...com>
Message-Id: <62115b277dab49ea97da5633f8522daf@...com>
Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 arch/x86/kvm/x86.c |    8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -9429,12 +9429,16 @@ static void vcpu_load_eoi_exitmap(struct
 	if (!kvm_apic_hw_enabled(vcpu->arch.apic))
 		return;
 
-	if (to_hv_vcpu(vcpu))
+	if (to_hv_vcpu(vcpu)) {
 		bitmap_or((ulong *)eoi_exit_bitmap,
 			  vcpu->arch.ioapic_handled_vectors,
 			  to_hv_synic(vcpu)->vec_bitmap, 256);
+		static_call(kvm_x86_load_eoi_exitmap)(vcpu, eoi_exit_bitmap);
+		return;
+	}
 
-	static_call(kvm_x86_load_eoi_exitmap)(vcpu, eoi_exit_bitmap);
+	static_call(kvm_x86_load_eoi_exitmap)(
+		vcpu, (u64 *)vcpu->arch.ioapic_handled_vectors);
 }
 
 void kvm_arch_mmu_notifier_invalidate_range(struct kvm *kvm,