linux-kernel - [PATCH] KVM: x86: Fix uninitialized eoi_exit_bitmap usage in vcpu_load_eoi

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Message-ID: <1300eda19bce40d5a539bc431446da5e@jd.com>
Date:   Sat, 13 Nov 2021 10:20:19 +0000
From:   黄乐 <huangle1@...com>
To:     "pbonzini@...hat.com" <pbonzini@...hat.com>,
        "vkuznets@...hat.com" <vkuznets@...hat.com>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: [PATCH] KVM: x86: Fix uninitialized eoi_exit_bitmap usage in
 vcpu_load_eoi_exitmap()

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.

Signed-off-by: Huang Le <huangle1@...com>
---
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index dc7eb5fddfd3..0699832504c9 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -9547,11 +9547,14 @@ static void vcpu_load_eoi_exitmap(struct kvm_vcpu *vcpu)
 	if (!kvm_apic_hw_enabled(vcpu->arch.apic))
 		return;
 
-	if (to_hv_vcpu(vcpu))
-		bitmap_or((ulong *)eoi_exit_bitmap,
-			  vcpu->arch.ioapic_handled_vectors,
-			  to_hv_synic(vcpu)->vec_bitmap, 256);
+	if (!to_hv_vcpu(vcpu)) {
+		static_call(kvm_x86_load_eoi_exitmap)(
+			vcpu, (u64 *)vcpu->arch.ioapic_handled_vectors);
+		return;
+	}
 
+	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);
 }