Paul E. McKenney
2013-Sep-25 01:35 UTC
[Bridge] [PATCH tip/core/rcu 12/13] bonding/bond_main: Apply rcu_access_pointer() to avoid sparse false positive
From: "Paul E. McKenney" <paulmck at 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 uses in
bond_change_active_slave(), bond_enslave(), and __bond_release_one()
are legitimate: They are assigning a pointer to an element from an
RCU-protected list (or a NULL pointer), and all elements of this list
are already visible to caller.
This commit therefore silences these false positives either by laundering
the pointers using rcu_access_pointer() as suggested by Josh Triplett,
or by using RCU_INIT_POINTER() for NULL pointer assignments.
Reported-by: kbuild test robot <fengguang.wu at intel.com>
Signed-off-by: Paul E. McKenney <paulmck at linux.vnet.ibm.com>
Cc: Stephen Hemminger <stephen at networkplumber.org>
Cc: "David S. Miller" <davem at davemloft.net>
Cc: bridge at lists.linux-foundation.org
Cc: netdev at vger.kernel.org
---
drivers/net/bonding/bond_main.c | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)
diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
index 72df399..2f276b9 100644
--- a/drivers/net/bonding/bond_main.c
+++ b/drivers/net/bonding/bond_main.c
@@ -890,7 +890,8 @@ void bond_change_active_slave(struct bonding *bond, struct
slave *new_active)
if (new_active)
bond_set_slave_active_flags(new_active);
} else {
- rcu_assign_pointer(bond->curr_active_slave, new_active);
+ rcu_assign_pointer(bond->curr_active_slave,
+ rcu_access_pointer(new_active));
}
if (bond->params.mode == BOND_MODE_ACTIVEBACKUP) {
@@ -1601,7 +1602,8 @@ int bond_enslave(struct net_device *bond_dev, struct
net_device *slave_dev)
* so we can change it without calling change_active_interface()
*/
if (!bond->curr_active_slave && new_slave->link ==
BOND_LINK_UP)
- rcu_assign_pointer(bond->curr_active_slave, new_slave);
+ rcu_assign_pointer(bond->curr_active_slave,
+ rcu_access_pointer(new_slave));
break;
} /* switch(bond_mode) */
@@ -1801,7 +1803,7 @@ static int __bond_release_one(struct net_device *bond_dev,
}
if (all) {
- rcu_assign_pointer(bond->curr_active_slave, NULL);
+ RCU_INIT_POINTER(bond->curr_active_slave, NULL);
} else if (oldcurrent == slave) {
/*
* Note that we hold RTNL over this sequence, so there
--
1.8.1.5