Fix buffer overrun in ZSTD_loadDictEntropyStats()

The table log set by `FSE_readNCount()` was not checked in
`ZSTD_loadDictEntropyStats()`.  This caused `FSE_buildCTable()`
to stack/heap overflow in a few places.

The benchmarks look good, there is no obvious compression performance regression:

  > ./zstds/zstd.opt.0 -i10 -b1 -e10 ~/bench/silesia.tar
   1#silesia.tar       : 211988480 ->  73656930 (2.878), 271.6 MB/s , 716.8 MB/s
   2#silesia.tar       : 211988480 ->  70162842 (3.021), 204.8 MB/s , 671.1 MB/s
   3#silesia.tar       : 211988480 ->  66997986 (3.164), 156.8 MB/s , 658.6 MB/s
   4#silesia.tar       : 211988480 ->  66002591 (3.212), 136.4 MB/s , 665.3 MB/s
   5#silesia.tar       : 211988480 ->  65008480 (3.261),  98.9 MB/s , 647.0 MB/s
   6#silesia.tar       : 211988480 ->  62979643 (3.366),  65.2 MB/s , 670.4 MB/s
   7#silesia.tar       : 211988480 ->  61974560 (3.421),  44.9 MB/s , 688.2 MB/s
   8#silesia.tar       : 211988480 ->  61028308 (3.474),  32.4 MB/s , 711.9 MB/s
   9#silesia.tar       : 211988480 ->  60416751 (3.509),  21.1 MB/s , 718.1 MB/s
  10#silesia.tar       : 211988480 ->  60174239 (3.523),  22.2 MB/s , 721.8 MB/s

  > ./compress_zstds/zstd.opt.1 -i10 -b1 -e10 ~/bench/silesia.tar
   1#silesia.tar       : 211988480 ->  73656930 (2.878), 273.8 MB/s , 722.0 MB/s
   2#silesia.tar       : 211988480 ->  70162842 (3.021), 203.2 MB/s , 666.6 MB/s
   3#silesia.tar       : 211988480 ->  66997986 (3.164), 157.4 MB/s , 666.5 MB/s
   4#silesia.tar       : 211988480 ->  66002591 (3.212), 132.1 MB/s , 661.9 MB/s
   5#silesia.tar       : 211988480 ->  65008480 (3.261),  96.8 MB/s , 641.6 MB/s
   6#silesia.tar       : 211988480 ->  62979643 (3.366),  63.1 MB/s , 677.0 MB/s
   7#silesia.tar       : 211988480 ->  61974560 (3.421),  44.3 MB/s , 678.2 MB/s
   8#silesia.tar       : 211988480 ->  61028308 (3.474),  33.1 MB/s , 708.9 MB/s
   9#silesia.tar       : 211988480 ->  60416751 (3.509),  21.5 MB/s , 710.1 MB/s
  10#silesia.tar       : 211988480 ->  60174239 (3.523),  21.9 MB/s , 723.9 MB/s

diff --git a/lib/compress/zstd_compress.c b/lib/compress/zstd_compress.c
index e71873b03f55b844becf2ac2c9015441629a3529..c44ef3d41c86422589f719db15e146ef3efab5de 100644 (file)
--- a/lib/compress/zstd_compress.c
+++ b/lib/compress/zstd_compress.c
@@ -2471,25 +2471,28 @@ static size_t ZSTD_loadDictEntropyStats(ZSTD_CCtx* cctx, const void* dict, size_
     }
 
     {   short offcodeNCount[MaxOff+1];
-        unsigned offcodeMaxValue = MaxOff, offcodeLog = OffFSELog;
+        unsigned offcodeMaxValue = MaxOff, offcodeLog;
         size_t const offcodeHeaderSize = FSE_readNCount(offcodeNCount, &offcodeMaxValue, &offcodeLog, dictPtr, dictEnd-dictPtr);
         if (FSE_isError(offcodeHeaderSize)) return ERROR(dictionary_corrupted);
+        if (offcodeLog > OffFSELog) return ERROR(dictionary_corrupted);
         CHECK_E (FSE_buildCTable(cctx->offcodeCTable, offcodeNCount, offcodeMaxValue, offcodeLog), dictionary_corrupted);
         dictPtr += offcodeHeaderSize;
     }
 
     {   short matchlengthNCount[MaxML+1];
-        unsigned matchlengthMaxValue = MaxML, matchlengthLog = MLFSELog;
+        unsigned matchlengthMaxValue = MaxML, matchlengthLog;
         size_t const matchlengthHeaderSize = FSE_readNCount(matchlengthNCount, &matchlengthMaxValue, &matchlengthLog, dictPtr, dictEnd-dictPtr);
         if (FSE_isError(matchlengthHeaderSize)) return ERROR(dictionary_corrupted);
+        if (matchlengthLog > MLFSELog) return ERROR(dictionary_corrupted);
         CHECK_E (FSE_buildCTable(cctx->matchlengthCTable, matchlengthNCount, matchlengthMaxValue, matchlengthLog), dictionary_corrupted);
         dictPtr += matchlengthHeaderSize;
     }
 
     {   short litlengthNCount[MaxLL+1];
-        unsigned litlengthMaxValue = MaxLL, litlengthLog = LLFSELog;
+        unsigned litlengthMaxValue = MaxLL, litlengthLog;
         size_t const litlengthHeaderSize = FSE_readNCount(litlengthNCount, &litlengthMaxValue, &litlengthLog, dictPtr, dictEnd-dictPtr);
         if (FSE_isError(litlengthHeaderSize)) return ERROR(dictionary_corrupted);
+        if (litlengthLog > LLFSELog) return ERROR(dictionary_corrupted);
         CHECK_E(FSE_buildCTable(cctx->litlengthCTable, litlengthNCount, litlengthMaxValue, litlengthLog), dictionary_corrupted);
         dictPtr += litlengthHeaderSize;
     }