Make sure nSelectors is not out of range nSelectors is used in a loop from 0 to nSelectors to access selectorMtf which is UChar selectorMtf[BZ_MAX_SELECTORS]; so if nSelectors is bigger than BZ_MAX_SELECTORS it'll do an invalid memory access Fixes out of bounds access discovered while fuzzying karchive This was reported as CVE-2019-12900 BZ2_decompress in decompress.c in bzip2 through 1.0.6 has an out-of-bounds write when there are many selectors.