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

[Avi Kivity <avi@redhat.com>]

  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