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ALSA: Add a reference counter to card instance

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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
commit a0830dbd4e
11 changed files with 86 additions and 32 deletions
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3
include/sound/core.h
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@ -132,6 +132,7 @@ struct snd_card {
int shutdown; /* this card is going down */
int free_on_last_close; /* free in context of file_release */
wait_queue_head_t shutdown_sleep;
atomic_t refcount; /* refcount for disconnection */
struct device *dev; /* device assigned to this card */
struct device *card_dev; /* cardX object for sysfs */
@ -189,6 +190,7 @@ struct snd_minor {
const struct file_operations *f_ops; /* file operations */
void *private_data; /* private data for f_ops->open */
struct device *dev; /* device for sysfs */
struct snd_card *card_ptr; /* assigned card instance */
};
/* return a device pointer linked to each sound device as a parent */
@ -295,6 +297,7 @@ int snd_card_info_done(void);
int snd_component_add(struct snd_card *card, const char *component);
int snd_card_file_add(struct snd_card *card, struct file *file);
int snd_card_file_remove(struct snd_card *card, struct file *file);
void snd_card_unref(struct snd_card *card);
#define snd_card_set_dev(card, devptr) ((card)->dev = (devptr))