UPSTREAM: sr9700: sanity check for packet length

[ Upstream commit e9da0b56 ]

A malicious device can leak heap data to user space
providing bogus frame lengths. Introduce a sanity check.

Bug: 225469258
Signed-off-by: Oliver Neukum <oneukum@suse.com>
Reviewed-by: Grant Grundler <grundler@chromium.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Change-Id: I2f17bd57b5c4228d0420f716527316a878a34efd