linux-kernel - [PATCH 4.4 25/67] ALSA: control: Avoid kernel warnings from tlv ioctl with numid 0

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Date:	Wed, 27 Jan 2016 10:12:19 -0800
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, Dmitry Vyukov <dvyukov@...gle.com>,
	Takashi Iwai <tiwai@...e.de>
Subject: [PATCH 4.4 25/67] ALSA: control: Avoid kernel warnings from tlv ioctl with numid 0

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

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

From: Takashi Iwai <tiwai@...e.de>

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@...gle.com>
Signed-off-by: Takashi Iwai <tiwai@...e.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 sound/core/control.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/sound/core/control.c
+++ b/sound/core/control.c
@@ -1405,6 +1405,8 @@ 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) {