From 3b4a36722e5e518e4bdd3a215d8a1c5adc18e911 Mon Sep 17 00:00:00 2001 From: Takashi Iwai Date: Tue, 16 Oct 2012 13:05:59 +0200 Subject: [PATCH] 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 Signed-off-by: Takashi Iwai Signed-off-by: Ben Hutchings --- include/sound/core.h | 3 +++ sound/core/control.c | 3 +++ sound/core/hwdep.c | 5 +++- sound/core/init.c | 50 +++++++++++++++++++++++--------------- sound/core/oss/mixer_oss.c | 10 ++++++-- sound/core/oss/pcm_oss.c | 2 ++ sound/core/pcm_native.c | 9 +++++-- sound/core/rawmidi.c | 6 ++++- sound/core/sound.c | 11 +++++++-- sound/core/sound_oss.c | 10 ++++++-- 10 files changed, 79 insertions(+), 30 deletions(-) diff --git a/include/sound/core.h b/include/sound/core.h index 3be5ab782b99..222f11eb191e 100644 --- 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 819a5c579a39..699ccf54c01f 100644 --- 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 75ea16f35b1a..53a6ba5ad615 100644 --- 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 3ac49b1b7cb8..fa0f35b433d1 100644 --- 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 18297f7f2c55..05395aaeaa32 100644 --- 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 3cc4b86dfb7e..f3cf781f8e11 100644 --- 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 e62da93da538..c67994d99552 100644 --- 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 ebf6e49ad3d4..7d4f62ab6711 100644 --- 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 828af353ea9f..f18897687740 100644 --- 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 c70092043061..7442c7ac2469 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); -- 2.39.2