media: dvb-usb-v2: ce6230: fix null-ptr-deref in ce6230_i2c_master_xfer()

In ce6230_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 ce6230_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()")

Link: https://lore.kernel.org/linux-media/20230313092751.209496-1-harperchen1110@gmail.com
Signed-off-by: Wei Chen <harperchen1110@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>

diff --git a/drivers/media/usb/dvb-usb-v2/ce6230.c b/drivers/media/usb/dvb-usb-v2/ce6230.c
index 44540de1a206686fcc366a2a8701bf15fe5b221b..d3b5cb4a24daf9c47a4903a3618aee977abeafd3 100644 (file)
--- a/drivers/media/usb/dvb-usb-v2/ce6230.c
+++ b/drivers/media/usb/dvb-usb-v2/ce6230.c
@@ -101,6 +101,10 @@ static int ce6230_i2c_master_xfer(struct i2c_adapter *adap,
                if (num > i + 1 && (msg[i+1].flags & I2C_M_RD)) {
                        if (msg[i].addr ==
                                ce6230_zl10353_config.demod_address) {
+                               if (msg[i].len < 1) {
+                                       i = -EOPNOTSUPP;
+                                       break;
+                               }
                                req.cmd = DEMOD_READ;
                                req.value = msg[i].addr >> 1;
                                req.index = msg[i].buf[0];
@@ -117,6 +121,10 @@ static int ce6230_i2c_master_xfer(struct i2c_adapter *adap,
                } else {
                        if (msg[i].addr ==
                                ce6230_zl10353_config.demod_address) {
+                               if (msg[i].len < 1) {
+                                       i = -EOPNOTSUPP;
+                                       break;
+                               }
                                req.cmd = DEMOD_WRITE;
                                req.value = msg[i].addr >> 1;
                                req.index = msg[i].buf[0];