From 1e8ba6fba5050ec11bba90c8622aa2ed95ff711f Mon Sep 17 00:00:00 2001 From: Ingo Molnar Date: Mon, 12 Feb 2007 00:54:42 -0800 Subject: [PATCH] [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 Signed-off-by: Avi Kivity Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- drivers/kvm/kvm_main.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/drivers/kvm/kvm_main.c b/drivers/kvm/kvm_main.c index eb3931ca680a..9b79d3451f6f 100644 --- a/drivers/kvm/kvm_main.c +++ b/drivers/kvm/kvm_main.c @@ -272,7 +272,9 @@ static void kvm_free_physmem(struct kvm *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);