[patch v2] ALSA: opl3: small array underflow

[Dan Carpenter <dan.carpenter@oracle.com>]

We don't check for negatives so "pitchbend" can be SHRT_MIN here.  It
means that we can read up to 6 elements before the start of the
opl3_note_table[] array.

There are several ways we could fix this.  I have gone with what is
maybe the lazier approach of just changing negative values to zero.
Hopefully, people aren't passing negatives here anyway.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
---
v2: The first patch just chan->midi_pitchbend unsigned but Clemens
Ladisch pointed out that that breaks the API.

diff --git a/sound/drivers/opl3/opl3_midi.c b/sound/drivers/opl3/opl3_midi.c
index f62780e..0cb91dc 100644
--- a/sound/drivers/opl3/opl3_midi.c
+++ b/sound/drivers/opl3/opl3_midi.c
@@ -105,6 +105,8 @@ static void snd_opl3_calc_pitch(unsigned char *fnum, unsigned char *blocknum,
 		int pitchbend = chan->midi_pitchbend;
 		int segment;
 
+		if (pitchbend < 0)
+			pitchbend = 0;
 		if (pitchbend > 0x1FFF)
 			pitchbend = 0x1FFF;