linux-kernel - [PATCH 3.16.y-ckt 129/180] ALSA: control: Avoid kernel warnings from tlv ioctl with numid 0

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Message-Id: <1454538786-12215-130-git-send-email-luis.henriques@canonical.com>
Date:	Wed,  3 Feb 2016 22:32:15 +0000
From:	Luis Henriques <luis.henriques@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Takashi Iwai <tiwai@...e.de>,
	Luis Henriques <luis.henriques@...onical.com>
Subject: [PATCH 3.16.y-ckt 129/180] ALSA: control: Avoid kernel warnings from tlv ioctl with numid 0

3.16.7-ckt24 -stable review patch.  If anyone has any objections, please let me know.

---8<------------------------------------------------------------

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: Luis Henriques <luis.henriques@...onical.com>
---
 sound/core/control.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/sound/core/control.c b/sound/core/control.c
index 8cdf0a4b327b..1d395d865f1b 100644
--- a/sound/core/control.c
+++ b/sound/core/control.c
@@ -1324,6 +1324,8 @@ static int snd_ctl_tlv_ioctl(struct snd_ctl_file *file,
 		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) {