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ALSA: control: Simplify snd_ctl_elem_list() implementation

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This patch simplifies the code of snd_ctl_elem_list() in the following
ways:

- Avoid a vmalloc() temporary buffer but do copy in each iteration;
  the vmalloc buffer was introduced at the time we took the spinlock
  for the ctl element management.

- Use the standard list_for_each_entry() macro

- Merge two loops into one;
  it used to be a loop for skipping until offset becomes zero and
  another loop to copy the data.  They can be folded into a single
  loop easily.

Reviewed-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Tested-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
This commit is contained in:
Takashi Iwai 2017-05-22 17:43:04 +02:00
parent a02cb8f8de
commit 53e7bf4525
1 changed files with 25 additions and 43 deletions
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68
sound/core/control.c
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@ -747,11 +747,11 @@ static int snd_ctl_card_info(struct snd_card *card, struct snd_ctl_file * ctl,
static int snd_ctl_elem_list(struct snd_card *card,
struct snd_ctl_elem_list __user *_list)
{
struct list_head *plist;
struct snd_ctl_elem_list list;
struct snd_kcontrol *kctl;
struct snd_ctl_elem_id *dst, *id;
struct snd_ctl_elem_id id;
unsigned int offset, space, jidx;
int err = 0;
if (copy_from_user(&list, _list, sizeof(list)))
return -EFAULT;
@ -760,52 +760,34 @@ static int snd_ctl_elem_list(struct snd_card *card,
/* try limit maximum space */
if (space > 16384)
return -ENOMEM;
down_read(&card->controls_rwsem);
list.count = card->controls_count;
list.used = 0;
if (space > 0) {
/* allocate temporary buffer for atomic operation */
dst = vmalloc(space * sizeof(struct snd_ctl_elem_id));
if (dst == NULL)
return -ENOMEM;
down_read(&card->controls_rwsem);
list.count = card->controls_count;
plist = card->controls.next;
while (plist != &card->controls) {
if (offset == 0)
break;
kctl = snd_kcontrol(plist);
if (offset < kctl->count)
break;
offset -= kctl->count;
plist = plist->next;
}
list.used = 0;
id = dst;
while (space > 0 && plist != &card->controls) {
kctl = snd_kcontrol(plist);
for (jidx = offset; space > 0 && jidx < kctl->count; jidx++) {
snd_ctl_build_ioff(id, kctl, jidx);
id++;
space--;
list.used++;
list_for_each_entry(kctl, &card->controls, list) {
if (offset >= kctl->count) {
offset -= kctl->count;
continue;
}
for (jidx = offset; jidx < kctl->count; jidx++) {
snd_ctl_build_ioff(&id, kctl, jidx);
if (copy_to_user(list.pids + list.used, &id,
sizeof(id))) {
err = -EFAULT;
goto out;
}
list.used++;
if (!--space)
goto out;
}
plist = plist->next;
offset = 0;
}
up_read(&card->controls_rwsem);
if (list.used > 0 &&
copy_to_user(list.pids, dst,
list.used * sizeof(struct snd_ctl_elem_id))) {
vfree(dst);
return -EFAULT;
}
vfree(dst);
} else {
down_read(&card->controls_rwsem);
list.count = card->controls_count;
up_read(&card->controls_rwsem);
}
if (copy_to_user(_list, &list, sizeof(list)))
return -EFAULT;
return 0;
out:
up_read(&card->controls_rwsem);
if (!err && copy_to_user(_list, &list, sizeof(list)))
err = -EFAULT;
return err;
}
static bool validate_element_member_dimension(struct snd_ctl_elem_info *info)