[PATCH 3.2 64/87] ALSA: control: Avoid kernel warnings from tlv ioctl with numid 0

3.2.77-rc1 review patch.  If anyone has any objections, please let me know.

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

From: Takashi Iwai <redacted>

commit c0bcdbdff3ff73a54161fca3cb8b6cdbd0bb8762 upstream.

When a TLV ioctl with numid zero is handled, the driver may spew a
kernel warning with a stack trace at each call.  The check was
intended obviously only for a kernel driver, but not for a user
interaction.  Let's fix it.

This was spotted by syzkaller fuzzer.

Reported-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Takashi Iwai <redacted>
Signed-off-by: Ben Hutchings <redacted>
---
 sound/core/control.c | 2 ++
 1 file changed, 2 insertions(+)

--- a/sound/core/control.c
+++ b/sound/core/control.c

@@ -1321,6 +1321,8 @@ static int snd_ctl_tlv_ioctl(struct snd_
 		return -EFAULT;
 	if (tlv.length < sizeof(unsigned int) * 2)
 		return -EINVAL;
+	if (!tlv.numid)
+		return -EINVAL;
 	down_read(&card->controls_rwsem);
 	kctl = snd_ctl_find_numid(card, tlv.numid);
 	if (kctl == NULL) {