Hi Julius,
On Fri, 12 Jul 2013 17:30:16 -0700, Julius Werner jwerner@chromium.org wrote:
The existing USB configuration parsing code relies on the descriptors' own length values when reading through the configuration blob. Since the size of those descriptors is always well-defined, we should rather use the known sizes instead of trusting device-provided values to be correct. Also adds some safety to potential out-of-order descriptors.
Question from the offspring of an USB ignoramus and a Devil's advocate: if the device, rather than relying on well-known sizes, provides its own values for lengths, maybe it's because it will let you read or write only that much, and if you try to read more, you might put the device in an unclean, or worse, non-functional, state?
In that case, trying to read a well-known length instead could cause more issues than reading the device-maker-specified length, could it not?
BTW, what is the real-world issue (hardware, conditions, expected outcome, actual outcome) which made this change needed?
Amicalement,