sound/oss/opl3: validate voice and channel indexes

commit 4d00135a upstream.

User-controllable indexes for voice and channel values may cause reading
and writing beyond the bounds of their respective arrays, leading to
potentially exploitable memory corruption.  Validate these indexes.
Signed-off-by: Dan Rosenberg <drosenberg@vsecurity.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

sound/oss/opl3.c

@@ -848,6 +848,10 @@ static int opl3_load_patch(int dev, int format, const char __user *addr,
 
 static void opl3_panning(int dev, int voice, int value)
 {
+
+	if (voice < 0 || voice >= devc->nr_voice)
+		return;
+
 	devc->voc[voice].panning = value;
 }
 
@@ -1065,8 +1069,15 @@ static int opl3_alloc_voice(int dev, int chn, int note, struct voice_alloc_info
 
 static void opl3_setup_voice(int dev, int voice, int chn)
 {
-	struct channel_info *info =
-	&synth_devs[dev]->chn_info[chn];
+	struct channel_info *info;
+
+	if (voice < 0 || voice >= devc->nr_voice)
+		return;
+
+	if (chn < 0 || chn > 15)
+		return;
+
+	info = &synth_devs[dev]->chn_info[chn];
 
 	opl3_set_instr(dev, voice, info->pgm_num);