Subject: Re: [PATCH] igmp: fix ip_mc_sf_allow race

From: Eric Dumazet <[email-masked]>
Date: Mon, 04 Jan 2010 14:07:03 +0100

Le 04/01/2010 12:29, Flavio Leitner a écrit :
 
> Then, I tried using call_rcu() to avoid the problem you are saying,
> but when you stop the reproducer, sk_free() will warn printing 
> "optmem leakage.." because the rcu callback didn't run yet.
> 
> 

This is probably because your call_rcu() callback was trying to call sock_kfree_s() ?

 		rtnl_unlock();
		call_rcu(&iml->lock, callback_func)

callback_func()
{
	sock_kfree_s(sk, iml, sizeof(*iml));
}

Take a look at sock_kfree_s() definition :

void sock_kfree_s(struct sock *sk, void *mem, int size)
{
        kfree(mem);
        atomic_sub(size, &sk->sk_omem_alloc);
}

You can certainly try :

	rtnl_unlock();
	atomic_sub(sizeof(*iml), sk->sk_omem_alloc);
	call_rcu(&iml->rcu, kfree);

(immediate sk_omem_alloc handling, but deferred kfree())