[PATCH AUTOSEL 4.14 07/20] media: dvb-usb: digitv: fix null-ptr-deref in digitv_i2c_xfer()

Sasha Levin
2023-05-25T19:20:24Z

From: Wei Chen <harperchen1110@gmail.com>

[ Upstream commit 9ded5bd2a49ce3015b7c936743eec0a0e6e11f0c ]

In digitv_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 digitv_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()")

Link: https://lore.kernel.org/linux-media/20230313095008.1039689-1-harperchen1110@gmail.com
Signed-off-by: Wei Chen <harperchen1110@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/media/usb/dvb-usb/digitv.c | 4 ++++
1 file changed, 4 insertions(+)

diff --git a/drivers/media/usb/dvb-usb/digitv.c b/drivers/media/usb/dvb-usb/digitv.c
index 20d33f0544ed2..0e2cffa946f69 100644
--- a/drivers/media/usb/dvb-usb/digitv.c
+++ b/drivers/media/usb/dvb-usb/digitv.c
@@ -66,6 +66,10 @@ static int digitv_i2c_xfer(struct i2c_adapter *adap,struct i2c_msg msg[],int num
warn("more than 2 i2c messages at a time is not handled yet. TODO.");

for (i = 0; i < num; i++) {
+ if (msg[i].len < 1) {
+ i = -EOPNOTSUPP;
+ break;
+ }
/* write/read request */
if (i+1 < num && (msg[i+1].flags & I2C_M_RD)) {
if (digitv_ctrl_msg(d, USB_READ_COFDM, msg[i].buf[0], NULL, 0,
--
2.39.2