From: W. Felix Handte <w@felixhandte.com>
Date: Tue, 15 May 2018 19:45:37 +0000 (-0400)
Subject: Avoid Undefined Behavior in Match Ptr Calculation
X-Git-Tag: v1.3.5~3^2~44^2~4
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=9c92223468acca6e5a7082e4e09b1f6870df7aa4;p=thirdparty%2Fzstd.git

Avoid Undefined Behavior in Match Ptr Calculation
---

diff --git a/lib/compress/zstd_fast.c b/lib/compress/zstd_fast.c
index 09b1a8ec3..b21bc7683 100644
--- a/lib/compress/zstd_fast.c
+++ b/lib/compress/zstd_fast.c
@@ -99,10 +99,10 @@ size_t ZSTD_compressBlock_fast_generic(
         U32 const matchIndex = hashTable[h];
         const BYTE* match = base + matchIndex;
         const U32 repIndex = current + 1 - offset_1;
-        const BYTE* repBase = (dictMode == ZSTD_dictMatchState
+        const BYTE* repMatch = (dictMode == ZSTD_dictMatchState
                             && repIndex < prefixLowestIndex) ?
-                               dictBase - dictIndexDelta : base;
-        const BYTE* repMatch = repBase + repIndex;
+                               dictBase + (repIndex - dictIndexDelta) :
+                               base + repIndex;
         hashTable[h] = current;   /* update hash table */
 
         if (dictMode == ZSTD_dictMatchState