[PATCH] IB/cm: Fix possible use-after-free in ib_cm_cleanup()

[Wang Hai]

This module's remove path calls cancel_delayed_work(). However, that
function does not wait until the work function finishes. This means
that the callback function may still be running after the driver's
remove function has finished, which would result in a use-after-free.

Fix by calling cancel_delayed_work_sync(), which ensures that
the work is properly cancelled, no longer running, and unable
to re-schedule itself.

Fixes: 8575329d4f85 ("IB/cm: Fix timewait crash after module unload")
Reported-by: Hulk Robot <hulkci@xxxxxxxxxx>
Signed-off-by: Wang Hai <wanghai38@xxxxxxxxxx>
---
 drivers/infiniband/core/cm.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/infiniband/core/cm.c b/drivers/infiniband/core/cm.c
index c903b74f46a4..ae0af63f3271 100644
--- a/drivers/infiniband/core/cm.c
+++ b/drivers/infiniband/core/cm.c
@@ -4508,7 +4508,7 @@ static void __exit ib_cm_cleanup(void)
 
 	spin_lock_irq(&cm.lock);
 	list_for_each_entry(timewait_info, &cm.timewait_list, list)
-		cancel_delayed_work(&timewait_info->work.work);
+		cancel_delayed_work_sync(&timewait_info->work.work);
 	spin_unlock_irq(&cm.lock);
 
 	ib_unregister_client(&cm_client);
-- 
2.25.1