staging: comedi: dt3000: Fix signed integer overflow 'divider * base'
commit b4d98bc3 upstream. In `dt3k_ns_to_timer()` the following lines near the end of the function result in a signed integer overflow: prescale = 15; base = timer_base * (1 << prescale); divider = 65535; *nanosec = divider * base; (`divider`, `base` and `prescale` are type `int`, `timer_base` and `*nanosec` are type `unsigned int`. The value of `timer_base` will be either 50 or 100.) The main reason for the overflow is that the calculation for `base` is completely wrong. It should be: base = timer_base * (prescale + 1); which matches an earlier instance of this calculation in the same function. Reported-by: David Binderman <dcb314@hotmail.com> Cc: <stable@vger.kernel.org> Signed-off-by: Ian Abbott <abbotti@mev.co.uk> Link: https://lore.kernel.org/r/20190812111517.26803-1-abbotti@mev.co.ukSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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