Subject: Re: net: rcu warnings in ip6fl_get_first

From: Cong Wang <[email-masked]>
Date: Fri, 8 Feb 2013 01:38:29 +0000 (UTC)

On Thu, 07 Feb 2013 at 19:32 GMT, Sasha Levin <[email-masked]> 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))
 #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);	\