From a0830dbd4e42b38aefdf3fb61ba5019a1a99ea85 Mon Sep 17 00:00:00 2001 From: Takashi Iwai Date: Tue, 16 Oct 2012 13:05:59 +0200 Subject: 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 Cc: Signed-off-by: Takashi Iwai --- sound/core/sound_oss.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) (limited to 'sound/core/sound_oss.c') 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 @@ void *snd_lookup_oss_minor_data(unsigned int minor, int type) 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 @@ int snd_register_oss_device(int type, struct snd_card *card, int dev, 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); -- cgit v1.1