media: dvb-usb-v2: rtl28xxu: fix null-ptr-deref in rtl28xxu_i2c_xfer

In rtl28xxu_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 rtl28xxu_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/tencent_3623572106754AC2F266B316798B0F6CCA05@qq.com
Signed-off-by: Zhang Shurong <zhang_shurong@foxmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>

diff --git a/drivers/media/usb/dvb-usb-v2/rtl28xxu.c b/drivers/media/usb/dvb-usb-v2/rtl28xxu.c
index 795a012..f7884bb 100644 (file)
--- a/drivers/media/usb/dvb-usb-v2/rtl28xxu.c
+++ b/drivers/media/usb/dvb-usb-v2/rtl28xxu.c
@@ -176,6 +176,10 @@ static int rtl28xxu_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg msg[],
                        ret = -EOPNOTSUPP;
                        goto err_mutex_unlock;
                } else if (msg[0].addr == 0x10) {
+                       if (msg[0].len < 1 || msg[1].len < 1) {
+                               ret = -EOPNOTSUPP;
+                               goto err_mutex_unlock;
+                       }
                        /* method 1 - integrated demod */
                        if (msg[0].buf[0] == 0x00) {
                                /* return demod page from driver cache */
@@ -189,6 +193,10 @@ static int rtl28xxu_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg msg[],
                                ret = rtl28xxu_ctrl_msg(d, &req);
                        }
                } else if (msg[0].len < 2) {
+                       if (msg[0].len < 1) {
+                               ret = -EOPNOTSUPP;
+                               goto err_mutex_unlock;
+                       }
                        /* method 2 - old I2C */
                        req.value = (msg[0].buf[0] << 8) | (msg[0].addr << 1);
                        req.index = CMD_I2C_RD;
@@ -217,8 +225,16 @@ static int rtl28xxu_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg msg[],
                        ret = -EOPNOTSUPP;
                        goto err_mutex_unlock;
                } else if (msg[0].addr == 0x10) {
+                       if (msg[0].len < 1) {
+                               ret = -EOPNOTSUPP;
+                               goto err_mutex_unlock;
+                       }
                        /* method 1 - integrated demod */
                        if (msg[0].buf[0] == 0x00) {
+                               if (msg[0].len < 2) {
+                                       ret = -EOPNOTSUPP;
+                                       goto err_mutex_unlock;
+                               }
                                /* save demod page for later demod access */
                                dev->page = msg[0].buf[1];
                                ret = 0;
@@ -231,6 +247,10 @@ static int rtl28xxu_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg msg[],
                                ret = rtl28xxu_ctrl_msg(d, &req);
                        }
                } else if ((msg[0].len < 23) && (!dev->new_i2c_write)) {
+                       if (msg[0].len < 1) {
+                               ret = -EOPNOTSUPP;
+                               goto err_mutex_unlock;
+                       }
                        /* method 2 - old I2C */
                        req.value = (msg[0].buf[0] << 8) | (msg[0].addr << 1);
                        req.index = CMD_I2C_WR;