media: dvb-usb-v2: af9035: Fix null-ptr-deref in af9035_i2c_master_xfer

[ Upstream commit 7bf744f2de0a848fb1d717f5831b03db96feae89 ]

In af9035_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 af9035_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()")

Signed-off-by: Zhang Shurong <zhang_shurong@foxmail.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Sasha Levin <sashal@kernel.org>
[ moved variable declaration to fix build issues in older kernels - gregkh ]
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/media/usb/dvb-usb-v2/af9035.c b/drivers/media/usb/dvb-usb-v2/af9035.c
index 1e9c8d0..cd6f537 100644 (file)
--- a/drivers/media/usb/dvb-usb-v2/af9035.c
+++ b/drivers/media/usb/dvb-usb-v2/af9035.c
@@ -270,6 +270,7 @@ static int af9035_i2c_master_xfer(struct i2c_adapter *adap,
        struct dvb_usb_device *d = i2c_get_adapdata(adap);
        struct state *state = d_to_priv(d);
        int ret;
+       u32 reg;
 
        if (mutex_lock_interruptible(&d->i2c_mutex) < 0)
                return -EAGAIN;
@@ -322,8 +323,10 @@ static int af9035_i2c_master_xfer(struct i2c_adapter *adap,
                        ret = -EOPNOTSUPP;
                } else if ((msg[0].addr == state->af9033_i2c_addr[0]) ||
                           (msg[0].addr == state->af9033_i2c_addr[1])) {
+                       if (msg[0].len < 3 || msg[1].len < 1)
+                               return -EOPNOTSUPP;
                        /* demod access via firmware interface */
-                       u32 reg = msg[0].buf[0] << 16 | msg[0].buf[1] << 8 |
+                       reg = msg[0].buf[0] << 16 | msg[0].buf[1] << 8 |
                                        msg[0].buf[2];
 
                        if (msg[0].addr == state->af9033_i2c_addr[1])
@@ -381,17 +384,16 @@ static int af9035_i2c_master_xfer(struct i2c_adapter *adap,
                        ret = -EOPNOTSUPP;
                } else if ((msg[0].addr == state->af9033_i2c_addr[0]) ||
                           (msg[0].addr == state->af9033_i2c_addr[1])) {
+                       if (msg[0].len < 3)
+                               return -EOPNOTSUPP;
                        /* demod access via firmware interface */
-                       u32 reg = msg[0].buf[0] << 16 | msg[0].buf[1] << 8 |
+                       reg = msg[0].buf[0] << 16 | msg[0].buf[1] << 8 |
                                        msg[0].buf[2];
 
                        if (msg[0].addr == state->af9033_i2c_addr[1])
                                reg |= 0x100000;
 
-                       ret = (msg[0].len >= 3) ? af9035_wr_regs(d, reg,
-                                                                &msg[0].buf[3],
-                                                                msg[0].len - 3)
-                                               : -EOPNOTSUPP;
+                       ret = af9035_wr_regs(d, reg, &msg[0].buf[3], msg[0].len - 3);
                } else {
                        /* I2C write */
                        u8 buf[MAX_XFER_SIZE];