media: dvb-usb-v2: ec168: fix null-ptr-deref in ec168_i2c_xfer()

[ Upstream commit a6dcefcc08eca1bf4e3d213c97c3cfb75f377935 ]

In ec168_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.
If accessing msg[i].buf[0] without sanity check, null pointer 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/20230313085853.3252349-1-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>

diff --git a/drivers/media/usb/dvb-usb-v2/ec168.c b/drivers/media/usb/dvb-usb-v2/ec168.c
index e30305876840f415532d949193cecb3841da811b..1191e32407c77bf69d8a46a4a7a391b73c98d9c2 100644 (file)
--- a/drivers/media/usb/dvb-usb-v2/ec168.c
+++ b/drivers/media/usb/dvb-usb-v2/ec168.c
@@ -115,6 +115,10 @@ static int ec168_i2c_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].addr == ec168_ec100_config.demod_address) {
+                               if (msg[i].len < 1) {
+                                       i = -EOPNOTSUPP;
+                                       break;
+                               }
                                req.cmd = READ_DEMOD;
                                req.value = 0;
                                req.index = 0xff00 + msg[i].buf[0]; /* reg */
@@ -131,6 +135,10 @@ static int ec168_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg msg[],
                        }
                } else {
                        if (msg[i].addr == ec168_ec100_config.demod_address) {
+                               if (msg[i].len < 1) {
+                                       i = -EOPNOTSUPP;
+                                       break;
+                               }
                                req.cmd = WRITE_DEMOD;
                                req.value = msg[i].buf[1]; /* val */
                                req.index = 0xff00 + msg[i].buf[0]; /* reg */
@@ -139,6 +147,10 @@ static int ec168_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg msg[],
                                ret = ec168_ctrl_msg(d, &req);
                                i += 1;
                        } else {
+                               if (msg[i].len < 1) {
+                                       i = -EOPNOTSUPP;
+                                       break;
+                               }
                                req.cmd = WRITE_I2C;
                                req.value = msg[i].buf[0]; /* val */
                                req.index = 0x0100 + msg[i].addr; /* I2C addr */