[PATCH net -v2] [BUGFIX] bonding: use flush_delayed_work_sync inbond_close

[Mitsuo Hayasaka]

The bond_close() calls cancel_delayed_work() to cancel delayed works.
It, however, cannot cancel works that were already queued in workqueue.
The bond_open() initializes work->data, and proccess_one_work() refers
get_work_cwq(work)->wq->flags. The get_work_cwq() returns NULL when
work->data has been initialized. Thus, a panic occurs.

This patch uses flush_delayed_work_sync() instead of cancel_delayed_work()
in bond_close(). It cancels delayed timer and waits for work to finish
execution. So, it can avoid the null pointer dereference due to the
parallel executions of proccess_one_work() and initializing proccess
of bond_open().

Signed-off-by: Mitsuo Hayasaka <mitsuo.hayasaka.hu@xxxxxxxxxxx>
Reviewed-by: WANG Cong <xiyou.wangcong@xxxxxxxxx>
Cc: Jay Vosburgh <fubar@xxxxxxxxxx>
Cc: Andy Gospodarek <andy@xxxxxxxxxxxxx>
Cc: WANG Cong <xiyou.wangcong@xxxxxxxxx>
---

 drivers/net/bonding/bond_main.c |   10 +++++-----
 1 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
index de3d351..a4353f9 100644
--- a/drivers/net/bonding/bond_main.c
+++ b/drivers/net/bonding/bond_main.c
@@ -3504,27 +3504,27 @@ static int bond_close(struct net_device *bond_dev)
 	write_unlock_bh(&bond->lock);
 
 	if (bond->params.miimon) {  /* link check interval, in milliseconds. */
-		cancel_delayed_work(&bond->mii_work);
+		flush_delayed_work_sync(&bond->mii_work);
 	}
 
 	if (bond->params.arp_interval) {  /* arp interval, in milliseconds. */
-		cancel_delayed_work(&bond->arp_work);
+		flush_delayed_work_sync(&bond->arp_work);
 	}
 
 	switch (bond->params.mode) {
 	case BOND_MODE_8023AD:
-		cancel_delayed_work(&bond->ad_work);
+		flush_delayed_work_sync(&bond->ad_work);
 		break;
 	case BOND_MODE_TLB:
 	case BOND_MODE_ALB:
-		cancel_delayed_work(&bond->alb_work);
+		flush_delayed_work_sync(&bond->alb_work);
 		break;
 	default:
 		break;
 	}
 
 	if (delayed_work_pending(&bond->mcast_work))
-		cancel_delayed_work(&bond->mcast_work);
+		flush_delayed_work_sync(&bond->mcast_work);
 
 	if (bond_is_lb(bond)) {
 		/* Must be called only after all

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