linux-kernel - [PATCH 3.16 062/134] [media] ttusb2: limit messages to buffer size

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Date:   Fri, 18 Aug 2017 14:13:20 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org,
        "Mauro Carvalho Chehab" <mchehab@...pensource.com>,
        "Alyssa Milburn" <amilburn@...l.org>
Subject: [PATCH 3.16 062/134] [media] ttusb2: limit messages to buffer size

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

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

From: Alyssa Milburn <amilburn@...l.org>

commit a12b8ab8c5ff7ccd7b107a564743507c850a441d upstream.

Otherwise ttusb2_i2c_xfer can read or write beyond the end of static and
heap buffers.

Signed-off-by: Alyssa Milburn <amilburn@...l.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@...pensource.com>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/media/usb/dvb-usb/ttusb2.c | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

--- a/drivers/media/usb/dvb-usb/ttusb2.c
+++ b/drivers/media/usb/dvb-usb/ttusb2.c
@@ -78,6 +78,9 @@ static int ttusb2_msg(struct dvb_usb_dev
 	u8 *s, *r = NULL;
 	int ret = 0;
 
+	if (4 + rlen > 64)
+		return -EIO;
+
 	s = kzalloc(wlen+4, GFP_KERNEL);
 	if (!s)
 		return -ENOMEM;
@@ -381,6 +384,22 @@ static int ttusb2_i2c_xfer(struct i2c_ad
 		write_read = i+1 < num && (msg[i+1].flags & I2C_M_RD);
 		read = msg[i].flags & I2C_M_RD;
 
+		if (3 + msg[i].len > sizeof(obuf)) {
+			err("i2c wr len=%d too high", msg[i].len);
+			break;
+		}
+		if (write_read) {
+			if (3 + msg[i+1].len > sizeof(ibuf)) {
+				err("i2c rd len=%d too high", msg[i+1].len);
+				break;
+			}
+		} else if (read) {
+			if (3 + msg[i].len > sizeof(ibuf)) {
+				err("i2c rd len=%d too high", msg[i].len);
+				break;
+			}
+		}
+
 		obuf[0] = (msg[i].addr << 1) | (write_read | read);
 		if (read)
 			obuf[1] = 0;