rfkill: introduce RFKILL_STATE_MAX

While it is interesting to not add last-enum-markers because it allows gcc
to warn us of switch() statements missing a valid state, we really should
be handling memory corruption on a rfkill state with default clauses,
anyway.

So add RFKILL_STATE_MAX and use it where applicable.  It makes for safer
code in the long run.
Signed-off-by: Henrique de Moraes Holschuh <hmh@hmh.eng.br>
Acked-by: Ivo van Doorn <IvDoorn@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

include/linux/rfkill.h

@@ -49,6 +49,7 @@ enum rfkill_state {
 	RFKILL_STATE_SOFT_BLOCKED = 0,	/* Radio output blocked */
 	RFKILL_STATE_UNBLOCKED    = 1,	/* Radio output allowed */
 	RFKILL_STATE_HARD_BLOCKED = 2,	/* Output blocked, non-overrideable */
+	RFKILL_STATE_MAX,		/* marker for last valid state */
 };
 
 /*

net/rfkill/rfkill.c

@@ -201,6 +201,8 @@ static int rfkill_toggle_radio(struct rfkill *rfkill,
 		 * BLOCK even a transmitter that is already in state
 		 * RFKILL_STATE_HARD_BLOCKED */
 		break;
+	default:
+		return -EINVAL;
 	}
 
 	if (force || state != rfkill->state) {
@@ -234,6 +236,9 @@ static void __rfkill_switch_all(const enum rfkill_type type,
 {
 	struct rfkill *rfkill;
 
+	if (unlikely(state >= RFKILL_STATE_MAX))
+		return;
+
 	rfkill_global_states[type].current_state = state;
 	list_for_each_entry(rfkill, &rfkill_list, node) {
 		if ((!rfkill->user_claim) && (rfkill->type == type)) {
@@ -329,9 +334,7 @@ int rfkill_force_state(struct rfkill *rfkill, enum rfkill_state state)
 {
 	enum rfkill_state oldstate;
 
-	if (state != RFKILL_STATE_SOFT_BLOCKED &&
-	    state != RFKILL_STATE_UNBLOCKED &&
-	    state != RFKILL_STATE_HARD_BLOCKED)
+	if (unlikely(state >= RFKILL_STATE_MAX))
 		return -EINVAL;
 
 	mutex_lock(&rfkill->mutex);
@@ -727,6 +730,8 @@ int __must_check rfkill_register(struct rfkill *rfkill)
 		return -EINVAL;
 	if (rfkill->type >= RFKILL_TYPE_MAX)
 		return -EINVAL;
+	if (rfkill->state >= RFKILL_STATE_MAX)
+		return -EINVAL;
 
 	snprintf(dev->bus_id, sizeof(dev->bus_id),
 		 "rfkill%ld", (long)atomic_inc_return(&rfkill_no) - 1);