linux-kernel - [PATCH 1/2] KVM: VMX: fix invalid cpu passed to smp_call_function

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Message-ID: <50B6093B.7040404@linux.vnet.ibm.com>
Date:	Wed, 28 Nov 2012 20:53:15 +0800
From:	Xiao Guangrong <xiaoguangrong@...ux.vnet.ibm.com>
To:	Avi Kivity <avi@...hat.com>
CC:	Marcelo Tosatti <mtosatti@...hat.com>,
	Gleb Natapov <gleb@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>, KVM <kvm@...r.kernel.org>
Subject: [PATCH 1/2] KVM: VMX: fix invalid cpu passed to smp_call_function_single

In loaded_vmcs_clear, loaded_vmcs->cpu is the fist parameter passed to
smp_call_function_single, if the target cpu is downing (doing cpu hot remove),
loaded_vmcs->cpu can become -1 then -1 is passed to smp_call_function_single

It can be triggered when vcpu is being destroyed, loaded_vmcs_clear is called
in the preemptionable context

Signed-off-by: Xiao Guangrong <xiaoguangrong@...ux.vnet.ibm.com>
---
 arch/x86/kvm/vmx.c |    8 +++++---
 1 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 6599e45..29e8f42 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -1007,9 +1007,11 @@ static void __loaded_vmcs_clear(void *arg)

 static void loaded_vmcs_clear(struct loaded_vmcs *loaded_vmcs)
 {
-	if (loaded_vmcs->cpu != -1)
-		smp_call_function_single(
-			loaded_vmcs->cpu, __loaded_vmcs_clear, loaded_vmcs, 1);
+	int cpu = loaded_vmcs->cpu;
+
+	if (cpu != -1)
+		smp_call_function_single(cpu,
+			 __loaded_vmcs_clear, loaded_vmcs, 1);
 }

 static inline void vpid_sync_vcpu_single(struct vcpu_vmx *vmx)
-- 
1.7.7.6

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