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authorTakashi Iwai <tiwai@suse.de>2012-10-16 15:05:59 +0400
committerTakashi Iwai <tiwai@suse.de>2012-10-30 14:07:10 +0400
commita0830dbd4e42b38aefdf3fb61ba5019a1a99ea85 (patch)
tree4dc74b708a07b56d12ed72a34d0a2e0cb8c8b9d4 /sound/core/sound.c
parent888ea7d5ac6815ba16b3b3a20f665a92c7af6724 (diff)
downloadlinux-a0830dbd4e42b38aefdf3fb61ba5019a1a99ea85.tar.xz
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>
Diffstat (limited to 'sound/core/sound.c')
-rw-r--r--sound/core/sound.c11
1 files changed, 9 insertions, 2 deletions
diff --git a/sound/core/sound.c b/sound/core/sound.c
index 643976000ce8..89780c323f19 100644
--- a/sound/core/sound.c
+++ b/sound/core/sound.c
@@ -98,6 +98,10 @@ static void snd_request_other(int minor)
*
* Checks that a minor device with the specified type is registered, and returns
* its user data pointer.
+ *
+ * This function increments the reference counter of the card instance
+ * if an associated instance with the given minor number and type is found.
+ * The caller must call snd_card_unref() appropriately later.
*/
void *snd_lookup_minor_data(unsigned int minor, int type)
{
@@ -108,9 +112,11 @@ void *snd_lookup_minor_data(unsigned int minor, int type)
return NULL;
mutex_lock(&sound_mutex);
mreg = snd_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_mutex);
return private_data;
@@ -275,6 +281,7 @@ int snd_register_device_for_dev(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_mutex);
#ifdef CONFIG_SND_DYNAMIC_MINORS
minor = snd_find_free_minor(type);