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ALSA: Add a reference counter to card instance

Browse source 
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>
This commit is contained in:
Takashi Iwai 2012-10-16 13:05:59 +02:00
parent 888ea7d5ac
commit a0830dbd4e
11 changed files with 86 additions and 32 deletions
Download patch file Download diff file Expand all files Collapse all files

50
sound/core/init.c
View file

@ -213,6 +213,7 @@ int snd_card_create(int idx, const char *xid,
spin_lock_init(&card->files_lock);
INIT_LIST_HEAD(&card->files_list);
init_waitqueue_head(&card->shutdown_sleep);
atomic_set(&card->refcount, 0);
#ifdef CONFIG_PM
mutex_init(&card->power_lock);
init_waitqueue_head(&card->power_sleep);
@ -446,21 +447,36 @@ static int snd_card_do_free(struct snd_card *card)
return 0;
}
/**
* snd_card_unref - release the reference counter
* @card: the card instance
*
* Decrements the reference counter. When it reaches to zero, wake up
* the sleeper and call the destructor if needed.
*/
void snd_card_unref(struct snd_card *card)
{
if (atomic_dec_and_test(&card->refcount)) {
wake_up(&card->shutdown_sleep);
if (card->free_on_last_close)
snd_card_do_free(card);
}
}
EXPORT_SYMBOL(snd_card_unref);
int snd_card_free_when_closed(struct snd_card *card)
{
int free_now = 0;
int ret = snd_card_disconnect(card);
if (ret)
int ret;
atomic_inc(&card->refcount);
ret = snd_card_disconnect(card);
if (ret) {
atomic_dec(&card->refcount);
return ret;
}
spin_lock(&card->files_lock);
if (list_empty(&card->files_list))
free_now = 1;
else
card->free_on_last_close = 1;
spin_unlock(&card->files_lock);
if (free_now)
card->free_on_last_close = 1;
if (atomic_dec_and_test(&card->refcount))
snd_card_do_free(card);
return 0;
}
@ -474,7 +490,7 @@ int snd_card_free(struct snd_card *card)
return ret;
/* wait, until all devices are ready for the free operation */
wait_event(card->shutdown_sleep, list_empty(&card->files_list));
wait_event(card->shutdown_sleep, !atomic_read(&card->refcount));
snd_card_do_free(card);
return 0;
}
@ -886,6 +902,7 @@ int snd_card_file_add(struct snd_card *card, struct file *file)
return -ENODEV;
}
list_add(&mfile->list, &card->files_list);
atomic_inc(&card->refcount);
spin_unlock(&card->files_lock);
return 0;
}
@ -908,7 +925,6 @@ EXPORT_SYMBOL(snd_card_file_add);
int snd_card_file_remove(struct snd_card *card, struct file *file)
{
struct snd_monitor_file *mfile, *found = NULL;
int last_close = 0;
spin_lock(&card->files_lock);
list_for_each_entry(mfile, &card->files_list, list) {
@ -923,19 +939,13 @@ int snd_card_file_remove(struct snd_card *card, struct file *file)
break;
}
}
if (list_empty(&card->files_list))
last_close = 1;
spin_unlock(&card->files_lock);
if (last_close) {
wake_up(&card->shutdown_sleep);
if (card->free_on_last_close)
snd_card_do_free(card);
}
if (!found) {
snd_printk(KERN_ERR "ALSA card file remove problem (%p)\n", file);
return -ENOENT;
}
kfree(found);
snd_card_unref(card);
return 0;
}