[PATCH tip/core/rcu 03/13] bridge: Apply rcu_access_pointer() to avoid sparse false positive

[Paul E. McKenney]

From: "Paul E. McKenney" <paulmck@xxxxxxxxxxxxxxxxxx>

The sparse checking for rcu_assign_pointer() was recently upgraded
to reject non-__kernel address spaces.  This also rejects __rcu,
which is almost always the right thing to do.  However, the uses in
br_multicast_del_pg() and br_multicast_new_port_group() are legitimate:
They is assigning a pointer to an element from an RCU-protected list,
and all elements of this list are already visible to caller.

This commit therefore silences these false positives by laundering the
pointers using rcu_access_pointer() as suggested by Josh Triplett.

Reported-by: kbuild test robot <fengguang.wu@xxxxxxxxx>
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
Cc: Stephen Hemminger <stephen@xxxxxxxxxxxxxxxxxx>
Cc: "David S. Miller" <davem@xxxxxxxxxxxxx>
Cc: bridge@xxxxxxxxxxxxxxxxxxxxxxxxxx
Cc: netdev@xxxxxxxxxxxxxxx
---
 net/bridge/br_multicast.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/bridge/br_multicast.c b/net/bridge/br_multicast.c
index d1c5786..314c81c 100644
--- a/net/bridge/br_multicast.c
+++ b/net/bridge/br_multicast.c
@@ -267,7 +267,7 @@ static void br_multicast_del_pg(struct net_bridge *br,
 		if (p != pg)
 			continue;
 
-		rcu_assign_pointer(*pp, p->next);
+		rcu_assign_pointer(*pp, rcu_access_pointer(p->next));
 		hlist_del_init(&p->mglist);
 		del_timer(&p->timer);
 		call_rcu_bh(&p->rcu, br_multicast_free_pg);
@@ -646,7 +646,7 @@ struct net_bridge_port_group *br_multicast_new_port_group(
 	p->addr = *group;
 	p->port = port;
 	p->state = state;
-	rcu_assign_pointer(p->next, next);
+	rcu_assign_pointer(p->next, rcu_access_pointer(next));
 	hlist_add_head(&p->mglist, &port->mglist);
 	setup_timer(&p->timer, br_multicast_port_group_expired,
 		    (unsigned long)p);
-- 
1.8.1.5

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