[PATCH] media: af9035: prevent buffer overflow on write

[Jozef Balga <jozef.balga@xxxxxxxxx>]

media: af9035: prevents buffer overflow when less than 3 bytes are written to the device

When less than 3 bytes are written to the device, memcpy is called with
negative array size which leads to buffer overflow and kernel panic. This
patch adds a condition and returns -EOPNOTSUPP instead.
Fixes bugzilla issue 64871

Signed-off-by: Jozef Balga <jozef.balga@xxxxxxxxx>
---
 drivers/media/usb/dvb-usb-v2/af9035.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/media/usb/dvb-usb-v2/af9035.c b/drivers/media/usb/dvb-usb-v2/af9035.c
index 666d319d3d1a..e509713db623 100644
--- a/drivers/media/usb/dvb-usb-v2/af9035.c
+++ b/drivers/media/usb/dvb-usb-v2/af9035.c
@@ -402,8 +402,9 @@ static int af9035_i2c_master_xfer(struct i2c_adapter *adap,
                        if (msg[0].addr == state->af9033_i2c_addr[1])
                                reg |= 0x100000;
 
-                       ret = af9035_wr_regs(d, reg, &msg[0].buf[3],
-                                       msg[0].len - 3);
+                       ret = (msg[0].len > 3) ? af9035_wr_regs(d, reg,
+                                       &msg[0].buf[3], msg[0].len - 3)
+                                       : -EOPNOTSUPP;
                } else {
                        /* I2C write */
                        u8 buf[MAX_XFER_SIZE];
-- 
2.14.4