Re: net: rcu warnings in ip6fl_get_first

From: Cong Wang
Date: Thu Feb 07 2013 - 20:44:50 EST


On Thu, 07 Feb 2013 at 19:32 GMT, Sasha Levin <sasha.levin@xxxxxxxxxx> 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); \

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