ipv6: fix a lockdep splat

[ Upstream commit 44c3d0c1c0a880354e9de5d94175742e2c7c9683 ]

Silence lockdep false positive about rcu_dereference() being
used in the wrong context.

First one should use rcu_dereference_protected() as we own the spinlock.

Second one should be a normal assignation, as no barrier is needed.

Fixes: 18367681a10bd ("ipv6 flowlabel: Convert np->ipv6_fl_list to RCU.")
Reported-by: Dave Jones <davej@codemonkey.org.uk>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/net/ipv6/ip6_flowlabel.c b/net/ipv6/ip6_flowlabel.c
index 1f9ebe3cbb4ac042edd0b05754d1fc03cdfe73cd..dc2db4f7b182c4ebc1a8a51487a3d2e893955df9 100644 (file)
--- a/net/ipv6/ip6_flowlabel.c
+++ b/net/ipv6/ip6_flowlabel.c
@@ -540,12 +540,13 @@ int ipv6_flowlabel_opt(struct sock *sk, char __user *optval, int optlen)
                }
                spin_lock_bh(&ip6_sk_fl_lock);
                for (sflp = &np->ipv6_fl_list;
-                    (sfl = rcu_dereference(*sflp)) != NULL;
+                    (sfl = rcu_dereference_protected(*sflp,
+                                                     lockdep_is_held(&ip6_sk_fl_lock))) != NULL;
                     sflp = &sfl->next) {
                        if (sfl->fl->label == freq.flr_label) {
                                if (freq.flr_label == (np->flow_label&IPV6_FLOWLABEL_MASK))
                                        np->flow_label &= ~IPV6_FLOWLABEL_MASK;
-                               *sflp = rcu_dereference(sfl->next);
+                               *sflp = sfl->next;
                                spin_unlock_bh(&ip6_sk_fl_lock);
                                fl_release(sfl->fl);
                                kfree_rcu(sfl, rcu);