From: Oleg Nesterov <oleg@tv-sign.ru>

net/ipv4/ipvs/ip_vs_core.c

	module_exit
	    ip_vs_cleanup
		ip_vs_control_cleanup
		    cancel_rearming_delayed_work
	// done

This is unsafe.  The module may be unloaded and the memory may be freed
while defense_work's handler is still running/preempted.

Do flush_work(&defense_work.work) after cancel_rearming_delayed_work().

Alternatively, we could add flush_work() to cancel_rearming_delayed_work(),
but note that we can't change cancel_delayed_work() in the same manner
because it may be called from atomic context.

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Cc: "David S. Miller" <davem@davemloft.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 net/ipv4/ipvs/ip_vs_ctl.c |    1 +
 1 file changed, 1 insertion(+)

diff -puN net/ipv4/ipvs/ip_vs_ctl.c~ipvs-flush-defense_work-before-module-unload net/ipv4/ipvs/ip_vs_ctl.c
--- a/net/ipv4/ipvs/ip_vs_ctl.c~ipvs-flush-defense_work-before-module-unload
+++ a/net/ipv4/ipvs/ip_vs_ctl.c
@@ -2387,6 +2387,7 @@ void ip_vs_control_cleanup(void)
 	EnterFunction(2);
 	ip_vs_trash_cleanup();
 	cancel_rearming_delayed_work(&defense_work);
+	flush_work_keventd(&defense_work.work);
 	ip_vs_kill_estimator(&ip_vs_stats);
 	unregister_sysctl_table(sysctl_header);
 	proc_net_remove("ip_vs_stats");
_