From: Ingo Molnar <[EMAIL PROTECTED]>
Subject: [patch] KVM: fix vcpu freeing bug
vcpu_load() can return NULL and it sometimes does in failure paths (for
example when the userspace ABI version is too old) - causing a
preemption count underflow in the ->vcpu_free() later on. So check for
NULL.
Signed-off-by: Ingo Molnar <[EMAIL PROTECTED]>
Index: linux/drivers/kvm/kvm_main.c
===================================================================
--- linux.orig/drivers/kvm/kvm_main.c
+++ linux/drivers/kvm/kvm_main.c
@@ -357,7 +357,9 @@ static void kvm_free_physmem(struct kvm
static void kvm_free_vcpu(struct kvm_vcpu *vcpu)
{
- vcpu_load(vcpu->kvm, vcpu_slot(vcpu));
+ if (!vcpu_load(vcpu->kvm, vcpu_slot(vcpu)))
+ return;
+
kvm_mmu_destroy(vcpu);
vcpu_put(vcpu);
kvm_arch_ops->vcpu_free(vcpu);
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