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[libzstd] Fix UBSAN failure

dev
Nick Terrell 2017-06-19 15:12:28 -07:00
parent e11a5e4e82
commit 55f9cd4942
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 */
}
/* 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 */
if (offset) {
while ( (start > anchor)
&& (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++; }
offset_2 = offset_1; offset_1 = (U32)(offset - ZSTD_REP_MOVE);
}
/* store sequence */
_storeSequence:
{ size_t const litLength = start - anchor;