lib/x86/crc32: fix undefined behavior in VPCLMULQDQ optimized functions #404
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The specifications for _mm256_castsi128_si256() and _mm512_castsi128_si512() are bugged, as they leave the high bits undefined instead of zeroed as would be expected. Separate intrinsics _mm256_zextsi128_si256() and _mm512_zextsi128_si512() were later added to allow working around this defect. Use them. This fixes incorrect CRC checksums produced by crc32_x86_vpclmulqdq_avx512_vl512() when built with 'clang -O0'. Other cases are not known to have been affected. Resolves #403 Fixes: 5f2a0b4 ("lib/x86/crc32: add VPCLMULQDQ implementations of CRC-32")
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tested and verified. Fix works, thanks |
pps83
approved these changes
Nov 27, 2024
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Can you try asan, afaik it should catch that uninitialized use. llvm+asan is broken in visual studio |
libdeflate has been tested extensively with ASAN, MSAN, UBSAN, and valgrind. None of them can detect this case, unfortunately. |
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The specifications for _mm256_castsi128_si256() and _mm512_castsi128_si512() are bugged, as they leave the high bits undefined instead of zeroed as would be expected. Separate intrinsics _mm256_zextsi128_si256() and _mm512_zextsi128_si512() were later added to allow working around this defect. Use them.
This fixes incorrect CRC checksums produced by
crc32_x86_vpclmulqdq_avx512_vl512() when built with 'clang -O0'. Other cases are not known to have been affected.
Resolves #403 Fixes: 5f2a0b4 ("lib/x86/crc32: add VPCLMULQDQ implementations of CRC-32")