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[v2,tip/core/rcu,11/13] bridge/br_mdb: Apply rcu_access_pointer() to avoid sparse false positive

Message ID 1381354186-16285-11-git-send-email-paulmck@linux.vnet.ibm.com
State Not Applicable, archived
Delegated to: David Miller
Headers show

Commit Message

Paul E. McKenney Oct. 9, 2013, 9:29 p.m. UTC 
From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>

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 use in
__br_mdb_del() is legitimate: They are 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@intel.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Stephen Hemminger <stephen@networkplumber.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: bridge@lists.linux-foundation.org
Cc: netdev@vger.kernel.org
---
 net/bridge/br_mdb.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
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Patch

diff --git a/net/bridge/br_mdb.c b/net/bridge/br_mdb.c
index 85a09bb5ca51..3184c8812b49 100644
--- a/net/bridge/br_mdb.c
+++ b/net/bridge/br_mdb.c
@@ -447,7 +447,7 @@  static int __br_mdb_del(struct net_bridge *br, struct br_mdb_entry *entry)
 		if (p->port->state == BR_STATE_DISABLED)
 			goto unlock;
 
-		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);