linux-kernel - [PATCH] kvm: reset arch memslot info on memslot creation

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Date:	Wed, 10 Jul 2013 11:24:39 +0300
From:	"Michael S. Tsirkin" <mst@...hat.com>
To:	kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:	Gleb Natapov <gleb@...hat.com>, Paolo Bonzini <pbonzini@...hat.com>
Subject: [PATCH] kvm: reset arch memslot info on memslot creation

On x86, kvm_arch_create_memslot assumes that rmap/lpage_info for the
slot are zeroed out: if they weren't, error handling code after out_free
label will free memory which wasn't allocated here.
This always happens to be the case because on KVM_MR_DELETE we clear the
whole arch structure.  So there's no bug, but it's cleaner not to rely
on this here.

Make the code more robust by clearing the rmap/lpage_info explicitly.

Signed-off-by: Michael S. Tsirkin <mst@...hat.com>
---
 arch/x86/kvm/x86.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index e8ba99c..96e6eb4 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -6922,6 +6922,10 @@ int kvm_arch_create_memslot(struct kvm_memory_slot *slot, unsigned long npages)
 {
 	int i;

+	/* Reset in case slot had some rmap/lpage_info. */
+	memset(&slot->arch.rmap, 0, sizeof slot->arch.rmap);
+	memset(&slot->arch.lpage_info, 0, sizeof slot->arch.lpage_info);
+
 	for (i = 0; i < KVM_NR_PAGE_SIZES; ++i) {
 		unsigned long ugfn;
 		int lpages;
-- 
MST
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