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author | Yann Collet <cyan@fb.com> | 2018-05-06 01:24:11 (GMT) |
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committer | Yann Collet <cyan@fb.com> | 2018-05-06 01:24:11 (GMT) |
commit | af127334670a5e7b710bbd6adb71aa7c3ef0cd72 (patch) | |
tree | bab2c44f789bcd9b92a80802ca4de791e60b6e17 /lib/lz4.c | |
parent | d358e33faa87e0293f27f272a8579de73f4ba938 (diff) | |
download | lz4-af127334670a5e7b710bbd6adb71aa7c3ef0cd72.zip lz4-af127334670a5e7b710bbd6adb71aa7c3ef0cd72.tar.gz lz4-af127334670a5e7b710bbd6adb71aa7c3ef0cd72.tar.bz2 |
fixed frametest error
The error can be reproduced using following command :
./frametest -v -i100000000 -s1659 -t31096808
It's actually a bug in the stream LZ4 API,
when starting a new stream
and providing a first chunk to complete with size < MINMATCH.
In which case, the chunk becomes a dictionary.
No hash was generated and stored,
but the chunk is accessible as default position 0 points to dictStart,
and position 0 is still within MAX_DISTANCE.
Then, next attempt to read 32-bits from position 0 fails.
The issue would have been mitigated by starting from index 64 KB,
effectively eliminating position 0 as too far away.
The proper fix is to eliminate such "dictionary" as too small.
Which is what this patch does.
Diffstat (limited to 'lib/lz4.c')
-rw-r--r-- | lib/lz4.c | 13 |
1 files changed, 12 insertions, 1 deletions
@@ -767,6 +767,7 @@ LZ4_FORCE_INLINE int LZ4_compress_generic( } else if (dictDirective==usingExtDict) { if (matchIndex < startIndex) { DEBUGLOG(7, "extDict candidate: matchIndex=%5u < startIndex=%5u", matchIndex, startIndex); + assert(startIndex - matchIndex >= MINMATCH); match = dictBase + matchIndex; lowLimit = dictionary; } else { @@ -989,6 +990,7 @@ _last_literals: if (outputLimited == fillOutput) { *inputConsumed = (int) (((const char*)ip)-source); } + DEBUGLOG(5, "LZ4_compress_generic: compressed %i bytes into %i bytes", inputSize, (int)(((char*)op) - dest)); return (int)(((char*)op) - dest); } @@ -1255,12 +1257,19 @@ int LZ4_compress_fast_continue (LZ4_stream_t* LZ4_stream, const char* source, ch { const tableType_t tableType = byU32; LZ4_stream_t_internal* streamPtr = &LZ4_stream->internal_donotuse; - const BYTE* const dictEnd = streamPtr->dictionary + streamPtr->dictSize; + const BYTE* dictEnd = streamPtr->dictionary + streamPtr->dictSize; if (streamPtr->initCheck) return 0; /* Uninitialized structure detected */ LZ4_renormDictT(streamPtr, inputSize); /* avoid index overflow */ if (acceleration < 1) acceleration = ACCELERATION_DEFAULT; + /* invalidate tiny dictionaries */ + if (streamPtr->dictSize < 4) { + streamPtr->dictSize = 0; + streamPtr->dictionary = (const BYTE*)source; + dictEnd = (const BYTE*)source; + } + /* Check overlapping input/dictionary space */ { const BYTE* sourceEnd = (const BYTE*) source + inputSize; if ((sourceEnd > streamPtr->dictionary) && (sourceEnd < dictEnd)) { @@ -1402,6 +1411,8 @@ LZ4_FORCE_INLINE int LZ4_decompress_generic( const BYTE* const shortiend = iend - (endOnInput ? 14 : 8) /*maxLL*/ - 2 /*offset*/; const BYTE* const shortoend = oend - (endOnInput ? 14 : 8) /*maxLL*/ - 18 /*maxML*/; + DEBUGLOG(5, "LZ4_decompress_generic (srcSize:%i)", srcSize); + /* Special cases */ if ((partialDecoding) && (oexit > oend-MFLIMIT)) oexit = oend-MFLIMIT; /* targetOutputSize too high => just decode everything */ if ((endOnInput) && (unlikely(outputSize==0))) return ((srcSize==1) && (*ip==0)) ? 0 : -1; /* Empty output buffer */ |