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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Dan Carpenter <dan.carpenter@oracle.com>,
        Hans Verkuil <hverkuil-cisco@xs4all.nl>,
        Mauro Carvalho Chehab <mchehab+huawei@kernel.org>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 4.9 091/175] media: saa7146: fix array overflow in vidioc_s_audio()
Date:   Mon, 28 Dec 2020 13:49:04 +0100
Message-Id: <20201228124857.660257549@linuxfoundation.org>
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From: Dan Carpenter <dan.carpenter@oracle.com>

[ Upstream commit 8e4d86e241cf035d6d3467cd346e7ce490681937 ]

The "a->index" value comes from the user via the ioctl.  The problem is
that the shift can wrap resulting in setting "mxb->cur_audinput" to an
invalid value, which later results in an array overflow.

Fixes: 6680427791c9 ("[media] mxb: fix audio handling")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/media/pci/saa7146/mxb.c | 19 ++++++++++---------
 1 file changed, 10 insertions(+), 9 deletions(-)

diff --git a/drivers/media/pci/saa7146/mxb.c b/drivers/media/pci/saa7146/mxb.c
index 504d788076392..3e8753c9e1e47 100644
--- a/drivers/media/pci/saa7146/mxb.c
+++ b/drivers/media/pci/saa7146/mxb.c
@@ -652,16 +652,17 @@ static int vidioc_s_audio(struct file *file, void *fh, const struct v4l2_audio *
 	struct mxb *mxb = (struct mxb *)dev->ext_priv;
 
 	DEB_D("VIDIOC_S_AUDIO %d\n", a->index);
-	if (mxb_inputs[mxb->cur_input].audioset & (1 << a->index)) {
-		if (mxb->cur_audinput != a->index) {
-			mxb->cur_audinput = a->index;
-			tea6420_route(mxb, a->index);
-			if (mxb->cur_audinput == 0)
-				mxb_update_audmode(mxb);
-		}
-		return 0;
+	if (a->index >= 32 ||
+	    !(mxb_inputs[mxb->cur_input].audioset & (1 << a->index)))
+		return -EINVAL;
+
+	if (mxb->cur_audinput != a->index) {
+		mxb->cur_audinput = a->index;
+		tea6420_route(mxb, a->index);
+		if (mxb->cur_audinput == 0)
+			mxb_update_audmode(mxb);
 	}
-	return -EINVAL;
+	return 0;
 }
 
 #ifdef CONFIG_VIDEO_ADV_DEBUG
-- 
2.27.0