[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 <mingo@elte.hu>
Signed-off-by: Avi Kivity <avi@qumranet.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/drivers/kvm/kvm_main.c b/drivers/kvm/kvm_main.c
index eb3931c..9b79d34 100644
--- a/drivers/kvm/kvm_main.c
+++ b/drivers/kvm/kvm_main.c
@@ -272,7 +272,9 @@
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);