linux-kernel - [PATCH] media: dvb-usb-v2: rtl28xxu: Fix null-ptr-deref in rtl28xxu_i2c

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Date:   Sun,  7 May 2023 22:52:47 +0800
From:   Zhang Shurong <zhang_shurong@...mail.com>
To:     crope@....fi
Cc:     mchehab@...nel.org, linux-media@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Zhang Shurong <zhang_shurong@...mail.com>
Subject: [PATCH] media: dvb-usb-v2: rtl28xxu: Fix null-ptr-deref in rtl28xxu_i2c_xfer

In rtl28xxu_i2c_xfer, msg is controlled by user. When msg[i].buf
is null and msg[i].len is zero, former checks on msg[i].buf would be
passed. Malicious data finally reach rtl28xxu_i2c_xfer. If accessing
msg[i].buf[0] without sanity check, null ptr deref would happen.
We add check on msg[i].len to prevent crash.

Similar commit:
commit 0ed554fd769a
("media: dvb-usb: az6027: fix null-ptr-deref in az6027_i2c_xfer()")

Signed-off-by: Zhang Shurong <zhang_shurong@...mail.com>
---
 drivers/media/usb/dvb-usb-v2/rtl28xxu.c | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/drivers/media/usb/dvb-usb-v2/rtl28xxu.c b/drivers/media/usb/dvb-usb-v2/rtl28xxu.c
index 795a012d4020..f7884bb56fcc 100644
--- a/drivers/media/usb/dvb-usb-v2/rtl28xxu.c
+++ b/drivers/media/usb/dvb-usb-v2/rtl28xxu.c
@@ -176,6 +176,10 @@ static int rtl28xxu_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg msg[],
 			ret = -EOPNOTSUPP;
 			goto err_mutex_unlock;
 		} else if (msg[0].addr == 0x10) {
+			if (msg[0].len < 1 || msg[1].len < 1) {
+				ret = -EOPNOTSUPP;
+				goto err_mutex_unlock;
+			}
 			/* method 1 - integrated demod */
 			if (msg[0].buf[0] == 0x00) {
 				/* return demod page from driver cache */
@@ -189,6 +193,10 @@ static int rtl28xxu_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg msg[],
 				ret = rtl28xxu_ctrl_msg(d, &req);
 			}
 		} else if (msg[0].len < 2) {
+			if (msg[0].len < 1) {
+				ret = -EOPNOTSUPP;
+				goto err_mutex_unlock;
+			}
 			/* method 2 - old I2C */
 			req.value = (msg[0].buf[0] << 8) | (msg[0].addr << 1);
 			req.index = CMD_I2C_RD;
@@ -217,8 +225,16 @@ static int rtl28xxu_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg msg[],
 			ret = -EOPNOTSUPP;
 			goto err_mutex_unlock;
 		} else if (msg[0].addr == 0x10) {
+			if (msg[0].len < 1) {
+				ret = -EOPNOTSUPP;
+				goto err_mutex_unlock;
+			}
 			/* method 1 - integrated demod */
 			if (msg[0].buf[0] == 0x00) {
+				if (msg[0].len < 2) {
+					ret = -EOPNOTSUPP;
+					goto err_mutex_unlock;
+				}
 				/* save demod page for later demod access */
 				dev->page = msg[0].buf[1];
 				ret = 0;
@@ -231,6 +247,10 @@ static int rtl28xxu_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg msg[],
 				ret = rtl28xxu_ctrl_msg(d, &req);
 			}
 		} else if ((msg[0].len < 23) && (!dev->new_i2c_write)) {
+			if (msg[0].len < 1) {
+				ret = -EOPNOTSUPP;
+				goto err_mutex_unlock;
+			}
 			/* method 2 - old I2C */
 			req.value = (msg[0].buf[0] << 8) | (msg[0].addr << 1);
 			req.index = CMD_I2C_WR;
-- 
2.40.1