Re: [PATCH 5/8] KVM: Add kvm_get_irq_routing_entry() func

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 On 10/20/2010 10:26 AM, Sheng Yang wrote:
We need to query the entry later.


+struct kvm_kernel_irq_routing_entry *kvm_get_irq_routing_entry(struct kvm *kvm,
+							       int gsi)
+{
+	int count = 0;
+	struct kvm_kernel_irq_routing_entry *ei = NULL;
+	struct kvm_irq_routing_table *irq_rt;
+	struct hlist_node *n;
+
+	rcu_read_lock();
+	irq_rt = rcu_dereference(kvm->irq_routing);
+	if (gsi<  irq_rt->nr_rt_entries)
+		hlist_for_each_entry(ei, n,&irq_rt->map[gsi], link)
+			count++;
+	rcu_read_unlock();
+	if (count == 1)
+		return ei;
+
+	return NULL;
+}
+

I believe this is incorrect rcu usage. rcu_read_lock() prevents ei from being destroyed under us, but rcu_read_unlock() removes that protection, and a future dereference of ei may access freed memory.

--
error compiling committee.c: too many arguments to function

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