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Merge pull request #727 from terrelln/ubsan-failure

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[libzstd] Fix UBSAN failure
This commit is contained in:
Yann Collet 2017-06-19 15:43:17 -07:00 committed by GitHub
commit 405751abbc
1 changed files with 6 additions and 2 deletions
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8
lib/compress/zstd_compress.c
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@ -2136,15 +2136,19 @@ void ZSTD_compressBlock_lazy_generic(ZSTD_CCtx* ctx,
break; /* nothing found : store previous solution */ break; /* nothing found : store previous solution */
} }
/* NOTE:
* start[-offset+ZSTD_REP_MOVE-1] is undefined behavior.
* (-offset+ZSTD_REP_MOVE-1) is unsigned, and is added to start, which
* overflows the pointer, which is undefined behavior.
*/
/* catch up */ /* catch up */
if (offset) { if (offset) {
while ( (start > anchor) while ( (start > anchor)
&& (start > base+offset-ZSTD_REP_MOVE) && (start > base+offset-ZSTD_REP_MOVE)
&& (start[-1] == start[-1-offset+ZSTD_REP_MOVE]) ) /* only search for offset within prefix */ && (start[-1] == (start-offset+ZSTD_REP_MOVE)[-1]) ) /* only search for offset within prefix */
{ start--; matchLength++; } { start--; matchLength++; }
offset_2 = offset_1; offset_1 = (U32)(offset - ZSTD_REP_MOVE); offset_2 = offset_1; offset_1 = (U32)(offset - ZSTD_REP_MOVE);
} }
/* store sequence */ /* store sequence */
_storeSequence: _storeSequence:
{ size_t const litLength = start - anchor; { size_t const litLength = start - anchor;