[ALSA] Fix use after free in opl3_seq and opl3_oss

Modules: OPL3

Don't read from free'd memory.  Also make use of the return
value, and don't register the device if something went wrong
creating the port.

Coverity #954, #955

Signed-off-by: Dave Jones <davej@redhat.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

1 files changed, 7 insertions, 5 deletions

diff --git a/sound/drivers/opl3/opl3_oss.c b/sound/drivers/opl3/opl3_oss.c
index 0345ae647681..fccf019a6d85 100644
--- a/sound/drivers/opl3/opl3_oss.c
+++ b/sound/drivers/opl3/opl3_oss.c
@@ -104,8 +104,10 @@ static int snd_opl3_oss_create_port(struct snd_opl3 * opl3)
                                                           voices, voices,
                                                           name);
         if (opl3->oss_chset->port < 0) {
+                int port;
+                port = opl3->oss_chset->port;
                 snd_midi_channel_free_set(opl3->oss_chset);
-                return opl3->oss_chset->port;
+                return port;
         }
         return 0;
 }
@@ -136,10 +138,10 @@ void snd_opl3_init_seq_oss(struct snd_opl3 *opl3, char *name)
         arg->oper = oss_callback;
         arg->private_data = opl3;
 
-        snd_opl3_oss_create_port(opl3);
-
-        /* register to OSS synth table */
-        snd_device_register(opl3->card, dev);
+        if (snd_opl3_oss_create_port(opl3)) {
+                /* register to OSS synth table */
+                snd_device_register(opl3->card, dev);
+        }
 }
 
 /* unregister */