From: Nathan Moinvaziri <nathan@nathanm.com>
Date: Mon, 4 Jan 2021 05:16:40 +0000 (-0800)
Subject: Fixed previous match length not reset when match start reset.
X-Git-Tag: v2.0.0-RC1~4
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=446c6974fec0d3b8a55eef7ce36a249a9eb601ea;p=thirdparty%2Fzlib-ng.git

Fixed previous match length not reset when match start reset.
https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=24294
---

diff --git a/deflate.c b/deflate.c
index f85bbb46..4f781ab2 100644
--- a/deflate.c
+++ b/deflate.c
@@ -1254,7 +1254,12 @@ void Z_INTERNAL fill_window(deflate_state *s) {
          */
         if (s->strstart >= wsize+MAX_DIST(s)) {
             memcpy(s->window, s->window+wsize, (unsigned)wsize);
-            s->match_start = (s->match_start >= wsize) ? s->match_start - wsize : 0;
+            if (s->match_start >= wsize) {
+                s->match_start -= wsize;
+            } else {
+                s->match_start = 0;
+                s->prev_length = 0;
+            }
             s->strstart    -= wsize; /* we now have strstart >= MAX_DIST */
             s->block_start -= (int)wsize;
             if (s->insert > s->strstart)