ALSA: seq: Drop UMP events when no UMP-conversion is set

When a destination client is a user client in the legacy MIDI mode and
it sets the no-UMP-conversion flag, currently the all UMP events are
still passed as-is.  But this may confuse the user-space, because the
event packet size is different from the legacy mode.

Since we cannot handle UMP events in user clients unless it's running
in the UMP client mode, we should filter out those events instead of
accepting blindly.  This patch addresses it by slightly adjusting the
conditions for UMP event handling at the event delivery time.

Fixes: 329ffe1 ("ALSA: seq: Allow suppressing UMP conversions")
Link: https://lore.kernel.org/[email protected]
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Takashi Iwai <[email protected]>

sound/core/seq/seq_clientmgr.c

@@ -678,12 +678,18 @@ static int snd_seq_deliver_single_event(struct snd_seq_client *client,
 					  dest_port->time_real);
 
 #if IS_ENABLED(CONFIG_SND_SEQ_UMP)
-	if (!(dest->filter & SNDRV_SEQ_FILTER_NO_CONVERT)) {
-		if (snd_seq_ev_is_ump(event)) {
+	if (snd_seq_ev_is_ump(event)) {
+		if (!(dest->filter & SNDRV_SEQ_FILTER_NO_CONVERT)) {
 			result = snd_seq_deliver_from_ump(client, dest, dest_port,
 							  event, atomic, hop);
 			goto __skip;
-		} else if (snd_seq_client_is_ump(dest)) {
+		} else if (dest->type == USER_CLIENT &&
+			   !snd_seq_client_is_ump(dest)) {
+			result = 0; // drop the event
+			goto __skip;
+		}
+	} else if (snd_seq_client_is_ump(dest)) {
+		if (!(dest->filter & SNDRV_SEQ_FILTER_NO_CONVERT)) {
 			result = snd_seq_deliver_to_ump(client, dest, dest_port,
 							event, atomic, hop);
 			goto __skip;