netdev - Re: [PATCH] net: Fix sock freeing before sock_init_data() with __sk

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Message-ID: <20090831070733.GC5005@ff.dom.local>
Date:	Mon, 31 Aug 2009 07:07:33 +0000
From:	Jarek Poplawski <jarkao2@...il.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	David Miller <davem@...emloft.net>, netdev@...r.kernel.org
Subject: Re: [PATCH] net: Fix sock freeing before sock_init_data() with
	__sk_free()

On Mon, Aug 31, 2009 at 08:50:25AM +0200, Eric Dumazet wrote:
> Jarek Poplawski a écrit :
> > On Mon, Aug 31, 2009 at 08:26:43AM +0200, Eric Dumazet wrote:
> >> Jarek Poplawski a écrit :
> >>> After recent changes sk_free() frees socks conditionally and depends
> >>> on sk_wmem_alloc beeing set e.g. in sock_init_data(). But in some
> >>> cases sk_free() is called earlier, usually after other alloc errors.
> >>> This patch fixes it by exporting and using __sk_free() directly.
> > ...
> >> Very nice catch Jarek, but dont you think it would be cleaner to make sure
> >> we can call sk_free() right after sk_alloc() instead, and not exporting
> >> __sk_free() ?
> >>
> >> ie initialize wmem_alloc in sk_alloc() instead of initializing it in 
> >> sock_init_data() ?
> >>
> > 
> > Most probably it should be better. But I meant this fix for -net and
> > didn't wan't to break too much... So, if you're sure it's OK feel free
> > to send your version. (Or it could be changed like this in the -next.)
> 
> Well, patch is yours, not mine, and I am confident it is OK.

Well, it's from you, and I guess you'll sign off too, but if you
think so...
 
Signed-off-by: Jarek Poplawski <jarkao2@...il.com>

Thanks,
Jarek P.

> 
> We should check that no sk_alloc() user did a blind memset() or something
> strange like that, before calling sock_init_data() or sk_free()
> 
> diff --git a/net/core/sock.c b/net/core/sock.c
> index bbb25be..7633422 100644
> --- a/net/core/sock.c
> +++ b/net/core/sock.c
> @@ -1025,6 +1025,7 @@ struct sock *sk_alloc(struct net *net, int family, gfp_t priority,
>  		sk->sk_prot = sk->sk_prot_creator = prot;
>  		sock_lock_init(sk);
>  		sock_net_set(sk, get_net(net));
> +		atomic_set(&sk->sk_wmem_alloc, 1);
>  	}
>  
>  	return sk;
> @@ -1872,7 +1873,6 @@ void sock_init_data(struct socket *sock, struct sock *sk)
>  	 */
>  	smp_wmb();
>  	atomic_set(&sk->sk_refcnt, 1);
> -	atomic_set(&sk->sk_wmem_alloc, 1);
>  	atomic_set(&sk->sk_drops, 0);
>  }
>  EXPORT_SYMBOL(sock_init_data);
> 
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