[PATCH] media: dvb-frontends: w7090p: fix null-ptr-deref in w7090p_tuner_write_serpar and w7090p_tuner_read_serpar

[Alex Guo <alexguo1023@gmail.com>]

In w7090p_tuner_write_serpar, msg is controlled by user. When msg[0].buf is null and msg[0].len is zero, former checks on msg[0].buf would be passed. If accessing msg[0].buf[2] without sanity check, null pointer deref would happen. We add
check on msg[0].len to prevent crash.

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

Signed-off-by: Alex Guo <alexguo1023@gmail.com>
---
 drivers/media/dvb-frontends/dib7000p.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/media/dvb-frontends/dib7000p.c b/drivers/media/dvb-frontends/dib7000p.c
index 9a309e23443a..93e5e873103e 100644
--- a/drivers/media/dvb-frontends/dib7000p.c
+++ b/drivers/media/dvb-frontends/dib7000p.c
@@ -2193,6 +2193,8 @@ static int w7090p_tuner_write_serpar(struct i2c_adapter *i2c_adap, struct i2c_ms
 	struct dib7000p_state *state = i2c_get_adapdata(i2c_adap);
 	u8 n_overflow = 1;
 	u16 i = 1000;
+	if (msg[0].len < 3)
+		return -EOPNOTSUPP;
 	u16 serpar_num = msg[0].buf[0];
 
 	while (n_overflow == 1 && i) {
@@ -2212,6 +2214,8 @@ static int w7090p_tuner_read_serpar(struct i2c_adapter *i2c_adap, struct i2c_msg
 	struct dib7000p_state *state = i2c_get_adapdata(i2c_adap);
 	u8 n_overflow = 1, n_empty = 1;
 	u16 i = 1000;
+	if (msg[0].len < 1 || msg[1].len < 2)
+		return -EOPNOTSUPP;
 	u16 serpar_num = msg[0].buf[0];
 	u16 read_word;
 
-- 
2.34.1