[PATCH 3.16.y-ckt 128/165] ALSA: control: Add sanity checks for user ctl id name string

[Luis Henriques]

3.16.7-ckt9 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Takashi Iwai <tiwai at suse.de>

commit be3bb8236db2d0fcd705062ae2e2a9d75131222f upstream.

There was no check about the id string of user control elements, so we
accepted even a control element with an empty string, which is
obviously bogus.  This patch adds more sanity checks of id strings.

Signed-off-by: Takashi Iwai <tiwai at suse.de>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 sound/core/control.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/sound/core/control.c b/sound/core/control.c
index f0b0e14497a5..8cdf0a4b327b 100644
--- a/sound/core/control.c
+++ b/sound/core/control.c
@@ -1167,6 +1167,10 @@ static int snd_ctl_elem_add(struct snd_ctl_file *file,
 
 	if (info->count < 1)
 		return -EINVAL;
+	if (!*info->id.name)
+		return -EINVAL;
+	if (strnlen(info->id.name, sizeof(info->id.name)) >= sizeof(info->id.name))
+		return -EINVAL;
 	access = info->access == 0 ? SNDRV_CTL_ELEM_ACCESS_READWRITE :
 		(info->access & (SNDRV_CTL_ELEM_ACCESS_READWRITE|
 				 SNDRV_CTL_ELEM_ACCESS_INACTIVE|