[PATCH] ALSA: seq: Check UMP support for midi_version change

[Takashi Iwai <tiwai@xxxxxxx>]

When the kernel is built without UMP support but a user-space app
requires the midi_version > 0, the kernel should return an error.
Otherwise user-space assumes as if it were possible to deal,
eventually hitting serious errors later.

Fixes: 46397622a3fa ("ALSA: seq: Add UMP support")
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Takashi Iwai <tiwai@xxxxxxx>
---
 sound/core/seq/seq_clientmgr.c | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/sound/core/seq/seq_clientmgr.c b/sound/core/seq/seq_clientmgr.c
index fe2d7f901610..498952161cfb 100644
--- a/sound/core/seq/seq_clientmgr.c
+++ b/sound/core/seq/seq_clientmgr.c
@@ -1275,10 +1275,16 @@ static int snd_seq_ioctl_set_client_info(struct snd_seq_client *client,
 	if (client->type != client_info->type)
 		return -EINVAL;
 
-	/* check validity of midi_version field */
-	if (client->user_pversion >= SNDRV_PROTOCOL_VERSION(1, 0, 3) &&
-	    client_info->midi_version > SNDRV_SEQ_CLIENT_UMP_MIDI_2_0)
-		return -EINVAL;
+	if (client->user_pversion >= SNDRV_PROTOCOL_VERSION(1, 0, 3)) {
+		/* check validity of midi_version field */
+		if (client_info->midi_version > SNDRV_SEQ_CLIENT_UMP_MIDI_2_0)
+			return -EINVAL;
+
+		/* check if UMP is supported in kernel */
+		if (!IS_ENABLED(CONFIG_SND_SEQ_UMP) &&
+		    client_info->midi_version > 0)
+			return -EINVAL;
+	}
 
 	/* fill the info fields */
 	if (client_info->name[0])
-- 
2.43.0