linux-kernel - [PATCH] kvm: don't treat NULL parent_pte as multimapped in mmu_parent

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Message-ID: <4B460441.6090602@gmail.com>
Date:	Thu, 07 Jan 2010 16:56:49 +0100
From:	Roel Kluin <roel.kluin@...il.com>
To:	Avi Kivity <avi@...hat.com>, Marcelo Tosatti <mtosatti@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
	kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] kvm: don't treat NULL parent_pte as multimapped in mmu_parent_walk()

If a kvm_mmu_page is not multimapped but parent_pte is NULL
don't treat it as multimapped and dereference it.

Signed-off-by: Roel Kluin <roel.kluin@...il.com>
---
This wasn't tested and maybe I misunderstood so please review.

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 4c3e5b2..eb17287 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -1031,10 +1031,12 @@ static void mmu_parent_walk(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp,
 	struct kvm_mmu_page *parent_sp;
 	int i;
 
-	if (!sp->multimapped && sp->parent_pte) {
-		parent_sp = page_header(__pa(sp->parent_pte));
-		fn(vcpu, parent_sp);
-		mmu_parent_walk(vcpu, parent_sp, fn);
+	if (!sp->multimapped) {
+		if (sp->parent_pte) {
+			parent_sp = page_header(__pa(sp->parent_pte));
+			fn(vcpu, parent_sp);
+			mmu_parent_walk(vcpu, parent_sp, fn);
+		}
 		return;
 	}
 	hlist_for_each_entry(pte_chain, node, &sp->parent_ptes, link)

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