control: use reference-counted pid

Instead of storing the PID number, take a reference to the task's pid
structure.  This protects against duplicates due to PID overflows, and
using pid_vnr() ensures that the PID returned by snd_ctl_elem_info() is
correct as seen from the current namespace.

Signed-off-by: Clemens Ladisch <clemens@ladisch.de>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

4 files changed, 8 insertions, 5 deletions

diff --git a/include/sound/control.h b/include/sound/control.h
index 3517745d0a2d..112374dc0c58 100644
--- a/include/sound/control.h
+++ b/include/sound/control.h
@@ -86,10 +86,12 @@ struct snd_kctl_event {
 
 #define snd_kctl_event(n) list_entry(n, struct snd_kctl_event, list)
 
+struct pid;
+
 struct snd_ctl_file {
         struct list_head list;          /* list of all control files */
         struct snd_card *card;
-        pid_t pid;
+        struct pid *pid;
         int prefer_pcm_subdevice;
         int prefer_rawmidi_subdevice;
         wait_queue_head_t change_sleep;
diff --git a/sound/core/control.c b/sound/core/control.c
index 814d2cf1a34c..73dc10ac33f6 100644
--- a/sound/core/control.c
+++ b/sound/core/control.c
@@ -75,7 +75,7 @@ static int snd_ctl_open(struct inode *inode, struct file *file)
         ctl->card = card;
         ctl->prefer_pcm_subdevice = -1;
         ctl->prefer_rawmidi_subdevice = -1;
-        ctl->pid = current->pid;
+        ctl->pid = get_pid(task_pid(current));
         file->private_data = ctl;
         write_lock_irqsave(&card->ctl_files_rwlock, flags);
         list_add_tail(&ctl->list, &card->ctl_files);
@@ -125,6 +125,7 @@ static int snd_ctl_release(struct inode *inode, struct file *file)
                                 control->vd[idx].owner = NULL;
         up_write(&card->controls_rwsem);
         snd_ctl_empty_read_queue(ctl);
+        put_pid(ctl->pid);
         kfree(ctl);
         module_put(card->module);
         snd_card_file_remove(card, file);
@@ -672,7 +673,7 @@ static int snd_ctl_elem_info(struct snd_ctl_file *ctl,
                         info->access |= SNDRV_CTL_ELEM_ACCESS_LOCK;
                         if (vd->owner == ctl)
                                 info->access |= SNDRV_CTL_ELEM_ACCESS_OWNER;
-                        info->owner = vd->owner->pid;
+                        info->owner = pid_vnr(vd->owner->pid);
                 } else {
                         info->owner = -1;
                 }
diff --git a/sound/core/pcm.c b/sound/core/pcm.c
index c69c60b2a48a..8e2c7833614c 100644
--- a/sound/core/pcm.c
+++ b/sound/core/pcm.c
@@ -809,7 +809,7 @@ int snd_pcm_attach_substream(struct snd_pcm *pcm, int stream,
         card = pcm->card;
         read_lock(&card->ctl_files_rwlock);
         list_for_each_entry(kctl, &card->ctl_files, list) {
-                if (kctl->pid == current->pid) {
+                if (kctl->pid == task_pid(current)) {
                         prefer_subdevice = kctl->prefer_pcm_subdevice;
                         if (prefer_subdevice != -1)
                                 break;
diff --git a/sound/core/rawmidi.c b/sound/core/rawmidi.c
index c0adc14c91f0..8a81bdafce6e 100644
--- a/sound/core/rawmidi.c
+++ b/sound/core/rawmidi.c
@@ -415,7 +415,7 @@ static int snd_rawmidi_open(struct inode *inode, struct file *file)
                 subdevice = -1;
                 read_lock(&card->ctl_files_rwlock);
                 list_for_each_entry(kctl, &card->ctl_files, list) {
-                        if (kctl->pid == current->pid) {
+                        if (kctl->pid == task_pid(current)) {
                                 subdevice = kctl->prefer_rawmidi_subdevice;
                                 if (subdevice != -1)
                                         break;