media: anysee: fix null-ptr-deref in anysee_master_xfer

In anysee_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 anysee_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 0ed554fd
("media: dvb-usb: az6027: fix null-ptr-deref in az6027_i2c_xfer()")
Signed-off-by: Zhang Shurong <zhang_shurong@foxmail.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
[hverkuil: add spaces around +]

drivers/media/usb/dvb-usb-v2/anysee.c

@@ -202,7 +202,7 @@ static int anysee_master_xfer(struct i2c_adapter *adap, struct i2c_msg *msg,
 
 	while (i < num) {
 		if (num > i + 1 && (msg[i+1].flags & I2C_M_RD)) {
-			if (msg[i].len > 2 || msg[i+1].len > 60) {
+			if (msg[i].len != 2 || msg[i + 1].len > 60) {
 				ret = -EOPNOTSUPP;
 				break;
 			}