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>

1 files changed, 3 insertions, 2 deletions

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;
                 }