From dfc431fb3d03bc8abceeff0aa9197fd165171561 Mon Sep 17 00:00:00 2001
From: Yann Collet <cyan@fb.com>
Date: Fri, 28 May 2021 01:10:41 -0700
Subject: fix NULL ptr arithmetic at lz4:2299

---
 lib/lz4.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/lib/lz4.c b/lib/lz4.c
index 9659962..62a6f6c 100644
--- a/lib/lz4.c
+++ b/lib/lz4.c
@@ -2298,8 +2298,13 @@ int LZ4_freeStreamDecode (LZ4_streamDecode_t* LZ4_stream)
 int LZ4_setStreamDecode (LZ4_streamDecode_t* LZ4_streamDecode, const char* dictionary, int dictSize)
 {
     LZ4_streamDecode_t_internal* lz4sd = &LZ4_streamDecode->internal_donotuse;
-    lz4sd->prefixSize = (size_t) dictSize;
-    lz4sd->prefixEnd = (const BYTE*) dictionary + dictSize;
+    lz4sd->prefixSize = (size_t)dictSize;
+    if (dictSize) {
+        assert(dictionary != NULL);
+        lz4sd->prefixEnd = (const BYTE*) dictionary + dictSize;
+    } else {
+        lz4sd->prefixEnd = (const BYTE*) dictionary;
+    }
     lz4sd->externalDict = NULL;
     lz4sd->extDictSize  = 0;
     return 1;
-- 
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