ALSA: Add a reference counter to card instance

commit a0830dbd4e42b38aefdf3fb61ba5019a1a99ea85 upstream.

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>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/include/sound/core.h b/include/sound/core.h
index 3be5ab7..222f11e 100644 (file)
--- a/include/sound/core.h
+++ b/include/sound/core.h
@@ -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))
 

diff --git a/sound/core/control.c b/sound/core/control.c
index 819a5c5..699ccf5 100644 (file)
--- a/sound/core/control.c
+++ b/sound/core/control.c
@@ -86,6 +86,7 @@ static int snd_ctl_open(struct inode *inode, struct file *file)
        write_lock_irqsave(&card->ctl_files_rwlock, flags);
        list_add_tail(&ctl->list, &card->ctl_files);
        write_unlock_irqrestore(&card->ctl_files_rwlock, flags);
+       snd_card_unref(card);
        return 0;
 
       __error:
@@ -93,6 +94,8 @@ static int snd_ctl_open(struct inode *inode, struct file *file)
       __error2:
        snd_card_file_remove(card, file);
       __error1:
+       if (card)
+               snd_card_unref(card);
        return err;
 }
 

diff --git a/sound/core/hwdep.c b/sound/core/hwdep.c
index 75ea16f..53a6ba5 100644 (file)
--- a/sound/core/hwdep.c
+++ b/sound/core/hwdep.c
@@ -100,8 +100,10 @@ static int snd_hwdep_open(struct inode *inode, struct file * file)
        if (hw == NULL)
                return -ENODEV;
 
-       if (!try_module_get(hw->card->module))
+       if (!try_module_get(hw->card->module)) {
+               snd_card_unref(hw->card);
                return -EFAULT;
+       }
 
        init_waitqueue_entry(&wait, current);
        add_wait_queue(&hw->open_wait, &wait);
@@ -148,6 +150,7 @@ static int snd_hwdep_open(struct inode *inode, struct file * file)
        mutex_unlock(&hw->open_mutex);
        if (err < 0)
                module_put(hw->card->module);
+       snd_card_unref(hw->card);
        return err;
 }
 

diff --git a/sound/core/init.c b/sound/core/init.c
index 3ac49b1..fa0f35b 100644 (file)
--- a/sound/core/init.c
+++ b/sound/core/init.c
@@ -212,6 +212,7 @@ 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);
@@ -445,21 +446,36 @@ 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)
-               return ret;
+       int 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);
+       atomic_inc(&card->refcount);
+       ret = snd_card_disconnect(card);
+       if (ret) {
+               atomic_dec(&card->refcount);
+               return ret;
+       }
 
-       if (free_now)
+       card->free_on_last_close = 1;
+       if (atomic_dec_and_test(&card->refcount))
                snd_card_do_free(card);
        return 0;
 }
@@ -473,7 +489,7 @@ 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;
 }
@@ -854,6 +870,7 @@ 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;
 }
@@ -876,7 +893,6 @@ 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) {
@@ -891,19 +907,13 @@ 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;
 }
 

diff --git a/sound/core/oss/mixer_oss.c b/sound/core/oss/mixer_oss.c
index 18297f7..05395aa 100644 (file)
--- a/sound/core/oss/mixer_oss.c
+++ b/sound/core/oss/mixer_oss.c
@@ -52,14 +52,19 @@ static int snd_mixer_oss_open(struct inode *inode, struct file *file)
                                         SNDRV_OSS_DEVICE_TYPE_MIXER);
        if (card == NULL)
                return -ENODEV;
-       if (card->mixer_oss == NULL)
+       if (card->mixer_oss == NULL) {
+               snd_card_unref(card);
                return -ENODEV;
+       }
        err = snd_card_file_add(card, file);
-       if (err < 0)
+       if (err < 0) {
+               snd_card_unref(card);
                return err;
+       }
        fmixer = kzalloc(sizeof(*fmixer), GFP_KERNEL);
        if (fmixer == NULL) {
                snd_card_file_remove(card, file);
+               snd_card_unref(card);
                return -ENOMEM;
        }
        fmixer->card = card;
@@ -68,6 +73,7 @@ static int snd_mixer_oss_open(struct inode *inode, struct file *file)
        if (!try_module_get(card->module)) {
                kfree(fmixer);
                snd_card_file_remove(card, file);
+               snd_card_unref(card);
                return -EFAULT;
        }
        return 0;

diff --git a/sound/core/oss/pcm_oss.c b/sound/core/oss/pcm_oss.c
index 3cc4b86..f3cf781 100644 (file)
--- a/sound/core/oss/pcm_oss.c
+++ b/sound/core/oss/pcm_oss.c
@@ -2457,6 +2457,8 @@ static int snd_pcm_oss_open(struct inode *inode, struct file *file)
       __error2:
        snd_card_file_remove(pcm->card, file);
       __error1:
+       if (pcm)
+               snd_card_unref(pcm->card);
        return err;
 }
 

diff --git a/sound/core/pcm_native.c b/sound/core/pcm_native.c
index e62da93..c67994d 100644 (file)
--- a/sound/core/pcm_native.c
+++ b/sound/core/pcm_native.c
@@ -1628,6 +1628,7 @@ static int snd_pcm_link(struct snd_pcm_substream *substream, int fd)
  _end:
        write_unlock_irq(&snd_pcm_link_rwlock);
        up_write(&snd_pcm_link_rwsem);
+       snd_card_unref(substream1->pcm->card);
        fput(file);
        return res;
 }
@@ -2100,7 +2101,9 @@ static int snd_pcm_playback_open(struct inode *inode, struct file *file)
                return err;
        pcm = snd_lookup_minor_data(iminor(inode),
                                    SNDRV_DEVICE_TYPE_PCM_PLAYBACK);
-       return snd_pcm_open(file, pcm, SNDRV_PCM_STREAM_PLAYBACK);
+       err = snd_pcm_open(file, pcm, SNDRV_PCM_STREAM_PLAYBACK);
+       snd_card_unref(pcm->card);
+       return err;
 }
 
 static int snd_pcm_capture_open(struct inode *inode, struct file *file)
@@ -2111,7 +2114,9 @@ static int snd_pcm_capture_open(struct inode *inode, struct file *file)
                return err;
        pcm = snd_lookup_minor_data(iminor(inode),
                                    SNDRV_DEVICE_TYPE_PCM_CAPTURE);
-       return snd_pcm_open(file, pcm, SNDRV_PCM_STREAM_CAPTURE);
+       err = snd_pcm_open(file, pcm, SNDRV_PCM_STREAM_CAPTURE);
+       snd_card_unref(pcm->card);
+       return err;
 }
 
 static int snd_pcm_open(struct file *file, struct snd_pcm *pcm, int stream)

diff --git a/sound/core/rawmidi.c b/sound/core/rawmidi.c
index ebf6e49..7d4f62a 100644 (file)
--- a/sound/core/rawmidi.c
+++ b/sound/core/rawmidi.c
@@ -379,8 +379,10 @@ static int snd_rawmidi_open(struct inode *inode, struct file *file)
        if (rmidi == NULL)
                return -ENODEV;
 
-       if (!try_module_get(rmidi->card->module))
+       if (!try_module_get(rmidi->card->module)) {
+               snd_card_unref(rmidi->card);
                return -ENXIO;
+       }
 
        mutex_lock(&rmidi->open_mutex);
        card = rmidi->card;
@@ -440,6 +442,7 @@ static int snd_rawmidi_open(struct inode *inode, struct file *file)
 #endif
        file->private_data = rawmidi_file;
        mutex_unlock(&rmidi->open_mutex);
+       snd_card_unref(rmidi->card);
        return 0;
 
  __error:
@@ -447,6 +450,7 @@ static int snd_rawmidi_open(struct inode *inode, struct file *file)
  __error_card:
        mutex_unlock(&rmidi->open_mutex);
        module_put(rmidi->card->module);
+       snd_card_unref(rmidi->card);
        return err;
 }
 

diff --git a/sound/core/sound.c b/sound/core/sound.c
index 828af35..f188976 100644 (file)
--- a/sound/core/sound.c
+++ b/sound/core/sound.c
@@ -99,6 +99,10 @@ 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)
 {
@@ -109,9 +113,11 @@ 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);

diff --git a/sound/core/sound_oss.c b/sound/core/sound_oss.c
index c700920..7442c7a 100644 (file)
--- 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);