Problem: [security]: overflow in ex address parsing
Solution: Verify that lnum is positive, before substracting from
LONG_MAX
[security]: overflow in ex address parsing
When parsing relative ex addresses one may unintentionally cause an
overflow (because LONG_MAX - lnum will overflow for negative addresses).
So verify that lnum is actually positive before doing the overflow
check.
060623e4a3
Co-authored-by: Christian Brabandt <cb@256bit.org>