linux-kernel - [PATCH AUTOSEL 6.5 02/28] media: dvb-usb-v2: af9035: Fix null-ptr-deref in af9035_i2c_master

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Date:   Fri,  8 Sep 2023 20:35:36 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Zhang Shurong <zhang_shurong@...mail.com>,
        Hans Verkuil <hverkuil-cisco@...all.nl>,
        Sasha Levin <sashal@...nel.org>, crope@....fi,
        mchehab@...nel.org, linux-media@...r.kernel.org
Subject: [PATCH AUTOSEL 6.5 02/28] media: dvb-usb-v2: af9035: Fix null-ptr-deref in af9035_i2c_master_xfer

From: Zhang Shurong <zhang_shurong@...mail.com>

[ Upstream commit 7bf744f2de0a848fb1d717f5831b03db96feae89 ]

In af9035_i2c_master_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 af9035_i2c_master_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>
Signed-off-by: Hans Verkuil <hverkuil-cisco@...all.nl>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/media/usb/dvb-usb-v2/af9035.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/drivers/media/usb/dvb-usb-v2/af9035.c b/drivers/media/usb/dvb-usb-v2/af9035.c
index 1e9c8d01523be..33a2aa8907e65 100644
--- a/drivers/media/usb/dvb-usb-v2/af9035.c
+++ b/drivers/media/usb/dvb-usb-v2/af9035.c
@@ -322,6 +322,8 @@ static int af9035_i2c_master_xfer(struct i2c_adapter *adap,
 			ret = -EOPNOTSUPP;
 		} else if ((msg[0].addr == state->af9033_i2c_addr[0]) ||
 			   (msg[0].addr == state->af9033_i2c_addr[1])) {
+			if (msg[0].len < 3 || msg[1].len < 1)
+				return -EOPNOTSUPP;
 			/* demod access via firmware interface */
 			u32 reg = msg[0].buf[0] << 16 | msg[0].buf[1] << 8 |
 					msg[0].buf[2];
@@ -381,6 +383,8 @@ static int af9035_i2c_master_xfer(struct i2c_adapter *adap,
 			ret = -EOPNOTSUPP;
 		} else if ((msg[0].addr == state->af9033_i2c_addr[0]) ||
 			   (msg[0].addr == state->af9033_i2c_addr[1])) {
+			if (msg[0].len < 3)
+				return -EOPNOTSUPP;
 			/* demod access via firmware interface */
 			u32 reg = msg[0].buf[0] << 16 | msg[0].buf[1] << 8 |
 					msg[0].buf[2];
@@ -388,10 +392,7 @@ static int af9035_i2c_master_xfer(struct i2c_adapter *adap,
 			if (msg[0].addr == state->af9033_i2c_addr[1])
 				reg |= 0x100000;
 
-			ret = (msg[0].len >= 3) ? af9035_wr_regs(d, reg,
-							         &msg[0].buf[3],
-							         msg[0].len - 3)
-					        : -EOPNOTSUPP;
+			ret = af9035_wr_regs(d, reg, &msg[0].buf[3], msg[0].len - 3);
 		} else {
 			/* I2C write */
 			u8 buf[MAX_XFER_SIZE];
-- 
2.40.1