ALSA: line6: fix stack overflow in line6_midi_transmit

Correctly calculate available space including the size of the chunk
buffer. This fixes a buffer overflow when multiple MIDI sysex
messages are sent to a PODxt device.

Signed-off-by: Artem Egorkine <[email protected]>
Cc: <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Takashi Iwai <[email protected]>

Author: arteme

sound/usb/line6/midi.c

@@ -44,7 +44,8 @@ static void line6_midi_transmit(struct snd_rawmidi_substream *substream)
 	int req, done;
 
 	for (;;) {
-		req = min(line6_midibuf_bytes_free(mb), line6->max_packet_size);
+		req = min3(line6_midibuf_bytes_free(mb), line6->max_packet_size,
+			   LINE6_FALLBACK_MAXPACKETSIZE);
 		done = snd_rawmidi_transmit_peek(substream, chunk, req);
 
 		if (done == 0)