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Message-ID: <20130208191932.GG2666@linux.vnet.ibm.com>
Date: Fri, 8 Feb 2013 11:19:32 -0800
From: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To: Cong Wang <xiyou.wangcong@...il.com>
Cc: linux-kernel@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: net: rcu warnings in ip6fl_get_first
On Fri, Feb 08, 2013 at 01:38:29AM +0000, Cong Wang wrote:
> On Thu, 07 Feb 2013 at 19:32 GMT, Sasha Levin <sasha.levin@...cle.com> wrote:
> > Hi guys,
> >
> > I got the following while fuzzing with trinity inside a KVM tools guest:
> >
> > [ 51.680236] ===============================
> > [ 51.681914] [ INFO: suspicious RCU usage. ]
> > [ 51.683610] 3.8.0-rc6-next-20130206-sasha-00028-g83214f7-dirty #276 Tainted: G W
> > [ 51.686703] -------------------------------
> > [ 51.688281] net/ipv6/ip6_flowlabel.c:671 suspicious rcu_dereference_check() usage!
> > [ 51.691345]
>
> It should use rcu_dereference_bh()...
>
> diff --git a/net/ipv6/ip6_flowlabel.c b/net/ipv6/ip6_flowlabel.c
> index ea42bf4..c50080f 100644
> --- a/net/ipv6/ip6_flowlabel.c
> +++ b/net/ipv6/ip6_flowlabel.c
> @@ -65,13 +65,13 @@ static DEFINE_SPINLOCK(ip6_fl_lock);
> static DEFINE_SPINLOCK(ip6_sk_fl_lock);
>
> #define for_each_fl_rcu(hash, fl) \
> - for (fl = rcu_dereference(fl_ht[(hash)]); \
> + for (fl = rcu_dereference_bh(fl_ht[(hash)]); \
> fl != NULL; \
> - fl = rcu_dereference(fl->next))
> + fl = rcu_dereference_hb(fl->next))
Small but important typo in the preceding line, should be:
+ fl = rcu_dereference_bh(fl->next))
Thanx, Paul
> #define for_each_fl_continue_rcu(fl) \
> - for (fl = rcu_dereference(fl->next); \
> + for (fl = rcu_dereference_bh(fl->next); \
> fl != NULL; \
> - fl = rcu_dereference(fl->next))
> + fl = rcu_dereference_bh(fl->next))
>
> #define for_each_sk_fl_rcu(np, sfl) \
> for (sfl = rcu_dereference_bh(np->ipv6_fl_list); \
>
> --
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