netdev - Re: [PATCH net-next v2 2/4] ipv6: enable IPV6_FLOWLABEL

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Date:	Tue, 5 Nov 2013 17:08:38 +0100
From:	Hannes Frederic Sowa <hannes@...essinduktion.org>
To:	Florent Fourcot <florent.fourcot@...t-bretagne.fr>
Cc:	netdev@...r.kernel.org
Subject: Re: [PATCH net-next v2 2/4] ipv6: enable IPV6_FLOWLABEL_MGR for getsockopt

On Tue, Nov 05, 2013 at 03:28:56PM +0100, Florent Fourcot wrote:
> +	spin_lock_bh(&ip6_fl_lock);
> +	rcu_read_lock_bh();
> +
> +	for_each_sk_fl_rcu(np, sfl) {
> +		if (sfl->fl->label == (np->flow_label & IPV6_FLOWLABEL_MASK)) {

The iteration is protected by rcu, so need to take the ip6_fl_lock. We should
lock the smallest region which needs to be protected. This is only the body of
the if.

Using fl->label without lock is fine, because it is immutable after interning.

> +			freq->flr_label = sfl->fl->label;
> +			freq->flr_dst = sfl->fl->dst;
> +			freq->flr_share = sfl->fl->share;
> +			freq->flr_expires = (sfl->fl->expires - jiffies) / HZ;
> +			freq->flr_linger = sfl->fl->linger / HZ;
> +
> +			rcu_read_unlock_bh();
> +			spin_unlock_bh(&ip6_fl_lock);

Please reverse these two lines then.

Could you take a look at your patch regarding fl6_renew, too? Can we
push locking into the function there, too?

Greetings,

  Hannes

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