ALSA: Add a reference counter to card instance
For more strict protection for wild disconnections, a refcount is
introduced to the card instance, and let it up/down when an object is
referred via snd_lookup_*() in the open ops.
The free-after-last-close check is also changed to check this refcount
instead of the empty list, too.
Reported-by: Matthieu CASTET <matthieu.castet@parrot.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
diff --git a/sound/core/sound_oss.c b/sound/core/sound_oss.c
index e952833..e1d79ee 100644
--- a/sound/core/sound_oss.c
+++ b/sound/core/sound_oss.c
@@ -40,6 +40,9 @@
static struct snd_minor *snd_oss_minors[SNDRV_OSS_MINORS];
static DEFINE_MUTEX(sound_oss_mutex);
+/* NOTE: This function increments the refcount of the associated card like
+ * snd_lookup_minor_data(); the caller must call snd_card_unref() appropriately
+ */
void *snd_lookup_oss_minor_data(unsigned int minor, int type)
{
struct snd_minor *mreg;
@@ -49,9 +52,11 @@
return NULL;
mutex_lock(&sound_oss_mutex);
mreg = snd_oss_minors[minor];
- if (mreg && mreg->type == type)
+ if (mreg && mreg->type == type) {
private_data = mreg->private_data;
- else
+ if (mreg->card_ptr)
+ atomic_inc(&mreg->card_ptr->refcount);
+ } else
private_data = NULL;
mutex_unlock(&sound_oss_mutex);
return private_data;
@@ -123,6 +128,7 @@
preg->device = dev;
preg->f_ops = f_ops;
preg->private_data = private_data;
+ preg->card_ptr = card;
mutex_lock(&sound_oss_mutex);
snd_oss_minors[minor] = preg;
minor_unit = SNDRV_MINOR_OSS_DEVICE(minor);
