RDMA/rxe: let rxe_reclassify_recv_socket() call sk_owner_put()

On kernels build with CONFIG_PROVE_LOCKING, CONFIG_MODULES
and CONFIG_DEBUG_LOCK_ALLOC 'rmmod rdma_rxe' is no longer
possible.

For the global recv sockets rxe_net_exit() is where we
call rxe_release_udp_tunnel-> udp_tunnel_sock_release(),
which means the sockets are destroyed before 'rmmod rdma_rxe'
finishes, so there's no need to protect against
rxe_recv_slock_key and rxe_recv_sk_key disappearing
while the sockets are still alive.

Fixes: 80a85a771deb ("RDMA/rxe: reclassify sockets in order to avoid false positives from lockdep")
Cc: Zhu Yanjun <[e-mail]>
Cc: Jason Gunthorpe <[e-mail]>
Cc: Leon Romanovsky <[e-mail]>
Cc: Shinichiro Kawasaki <[e-mail]>
Cc: [e-mail]
Cc: [e-mail]
Cc: [e-mail]
Signed-off-by: Stefan Metzmacher <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Reviewed-by: Zhu Yanjun <[e-mail]>
Tested-by: Shin'ichiro Kawasaki <[e-mail]>
Signed-off-by: Leon Romanovsky <[e-mail]>

drivers/infiniband/sw/rxe/rxe_net.c

···
 		break;
 	default:
 		WARN_ON_ONCE(1);
+		return;
 	}
+	/*
+	 * sock_lock_init_class_and_name() calls
+	 * sk_owner_set(sk, THIS_MODULE); in order
+	 * to make sure the referenced global
+	 * variables rxe_recv_slock_key and
+	 * rxe_recv_sk_key are not removed
+	 * before the socket is closed.
+	 *
+	 * However this prevents rxe_net_exit()
+	 * from being called and 'rmmod rdma_rxe'
+	 * is refused because of the references.
+	 *
+	 * For the global sockets in recv_sockets,
+	 * we are sure that rxe_net_exit() will call
+	 * rxe_release_udp_tunnel -> udp_tunnel_sock_release.
+	 *
+	 * So we don't need the additional reference to
+	 * our own (THIS_MODULE).
+	 */
+	sk_owner_put(sk);
+	/*
+	 * We also call sk_owner_clear() otherwise
+	 * sk_owner_put(sk) in sk_prot_free will
+	 * fail, which is called via
+	 * sk_free -> __sk_free -> sk_destruct
+	 * and sk_destruct calls __sk_destruct
+	 * directly or via call_rcu()
+	 * so sk_prot_free() might be called
+	 * after rxe_net_exit().
+	 */
+	sk_owner_clear(sk);
 #endif /* CONFIG_DEBUG_LOCK_ALLOC */
 }