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pgx_getword() and pgx_wordtoint() compute (1 << prec) and (1 << (prec - 1)) in 32-bit types. For prec = 32 (and prec = 0 in wordtoint's sign test) the shift exponent is out of range: undefined behavior, reproducible with a crafted .pgx under UBSan. Use uint_fast64_t for the mask and jas_seqent_t for the sign extension, and reject prec = 0 in the header validation since a zero-bit precision is meaningless (it also fed the prec - 1 shift). Fixes jasper-software#414.
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Summary
Fixes #414 — crafted
.pgxheaders trigger undefined behavior at two sites:pgx_getword():val &= (JAS_CAST(uint_fast32_t, 1) << prec) - 1— forprec = 32the shift exponent is out of range for 32-bituint_fast32_tpgx_wordtoint():(1 << prec),(1 << (prec - 1))— same problem forprec = 32, andprec = 0shifts by-1Fix
uint_fast64_t/jas_seqent_t, mirroring thebitstoint()fix patternprec < 1(a zero-bit precision is meaningless and previously slipped through to theprec - 1shift)Testing
Reproduced with the PoC attached to #414 under UBSan:
After the patch: no sanitizer report; malformed input is rejected cleanly.