net/net_namespace: Check the return value of register_pernet_subsys()

[ Upstream commit 0eb987c874dc93f9c9d85a6465dbde20fdd3884c ]

In net_ns_init(), register_pernet_subsys() could fail while registering
network namespace subsystems. The fix checks the return value and
sends a panic() on failure.
Signed-off-by: NAditya Pakki <pakki001@umn.edu>
Reviewed-by: NKirill Tkhai <ktkhai@virtuozzo.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>
Signed-off-by: NSasha Levin <sashal@kernel.org>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

net/core/net_namespace.c

@@ -913,7 +913,8 @@ static int __init net_ns_init(void)
 	init_net_initialized = true;
 	up_write(&pernet_ops_rwsem);
 
-	register_pernet_subsys(&net_ns_ops);
+	if (register_pernet_subsys(&net_ns_ops))
+		panic("Could not register network namespace subsystems");
 
 	rtnl_register(PF_UNSPEC, RTM_NEWNSID, rtnl_net_newid, NULL,
 		      RTNL_FLAG_DOIT_UNLOCKED);