netdev - [PATCH net-next-2.6 v2] net: sk_{detach|attach}

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Date:	Mon, 27 Sep 2010 18:07:30 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	David Miller <davem@...emloft.net>
Cc:	netdev <netdev@...r.kernel.org>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Subject: [PATCH net-next-2.6 v2] net: sk_{detach|attach}_filter() rcu fixes

Le lundi 27 septembre 2010 à 17:57 +0200, Eric Dumazet a écrit :
> sk_attach_filter() is run with socket locked.
> 
> Use the appropriate rcu_dereference_protected() instead of blocking BH,
> and rcu_dereference_bh().
> There is no point adding BH prevention and memory barrier.

Hmm, same thing can be done in sk_detach_filter, here is a v2.

Thanks

[PATCH net-next-2.6 v2] net: sk_{detach|attach}_filter() rcu fixes

sk_attach_filter() and sk_detach_filter() are run with socket locked.

Use the appropriate rcu_dereference_protected() instead of blocking BH,
and rcu_dereference_bh().
There is no point adding BH prevention and memory barrier.

Signed-off-by: Eric Dumazet <eric.dumazet@...il.com>
---
 net/core/filter.c |   10 ++++------
 1 file changed, 4 insertions(+), 6 deletions(-)

diff --git a/net/core/filter.c b/net/core/filter.c
index 52b051f..7adf503 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -638,10 +638,9 @@ int sk_attach_filter(struct sock_fprog *fprog, struct sock *sk)
 		return err;
 	}
 
-	rcu_read_lock_bh();
-	old_fp = rcu_dereference_bh(sk->sk_filter);
+	old_fp = rcu_dereference_protected(sk->sk_filter,
+					   sock_owned_by_user(sk));
 	rcu_assign_pointer(sk->sk_filter, fp);
-	rcu_read_unlock_bh();
 
 	if (old_fp)
 		sk_filter_delayed_uncharge(sk, old_fp);
@@ -654,14 +653,13 @@ int sk_detach_filter(struct sock *sk)
 	int ret = -ENOENT;
 	struct sk_filter *filter;
 
-	rcu_read_lock_bh();
-	filter = rcu_dereference_bh(sk->sk_filter);
+	filter = rcu_dereference_protected(sk->sk_filter,
+					   sock_owned_by_user(sk));
 	if (filter) {
 		rcu_assign_pointer(sk->sk_filter, NULL);
 		sk_filter_delayed_uncharge(sk, filter);
 		ret = 0;
 	}
-	rcu_read_unlock_bh();
 	return ret;
 }
 EXPORT_SYMBOL_GPL(sk_detach_filter);


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