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

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Date:	Mon, 31 Aug 2009 08:50:25 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Jarek Poplawski <jarkao2@...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()

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.

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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