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 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 ACCESS_ONCE() as suggested by Eric Dumazet and Josh Triplett, or by using RCU_INIT_POINTER() for NULL pointer assignments. 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 --- 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 72df399c4ab3..e4270ae1c0a8 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); + /* Both --rcu and visible, so ACCESS_ONCE() is OK. */ + ACCESS_ONCE(bond->curr_active_slave) = 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); + /* Both --rcu and visible, so ACCESS_ONCE() is OK. */ + ACCESS_ONCE(bond->curr_active_slave) = 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