sctp: handle invalid error codes without calling BUG()

The sctp_sf_eat_auth() function is supposed to return enum sctp_disposition
values but if the call to sctp_ulpevent_make_authkey() fails, it returns
-ENOMEM.

This results in calling BUG() inside the sctp_side_effects() function.
Calling BUG() is an over reaction and not helpful.  Call WARN_ON_ONCE()
instead.

This code predates git.
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/sctp/sm_sideeffect.c

@@ -1250,7 +1250,10 @@ static int sctp_side_effects(enum sctp_event_type event_type,
 	default:
 		pr_err("impossible disposition %d in state %d, event_type %d, event_id %d\n",
 		       status, state, event_type, subtype.chunk);
-		BUG();
+		error = status;
+		if (error >= 0)
+			error = -EINVAL;
+		WARN_ON_ONCE(1);
 		break;
 	}