The frame length and the offset (which depends on the device-supplied
frame type) are derived from device bytes, so validate both the source
read (against the response buffer) and the destination write (against
the image buffer) before copying.
A malicious or malfunctioning device could otherwise drive a negative
(huge once unsigned) or out-of-bounds length.
Note: the response is reassembled across several USB transfers, so the
bound here is the response buffer capacity rather than a single
transfer's actual_length.
Reported by: Keith Linneman (LinnemanLabs)
Marco Trevisan (Treviño)
44dd97bf5e