From 6456fae9ba8e72c74b2c0c499eaf09974604ff30 Mon Sep 17 00:00:00 2001
From: Bram Moolenaar <Bram@vim.org>
Date: Tue, 22 Feb 2022 13:37:31 +0000
Subject: [PATCH] patch 8.2.4440: crash with specific regexp pattern and string

Problem:    Crash with specific regexp pattern and string.
Solution:   Stop at the start of the string.
---
 src/regexp_bt.c                  |  5 +++++
 src/testdir/test_regexp_utf8.vim | 12 ++++++++++--
 src/version.c                    |  2 ++
 3 files changed, 17 insertions(+), 2 deletions(-)

diff --git a/src/regexp_bt.c b/src/regexp_bt.c
index 5f5e58f834fcd..4082f59d35cc3 100644
--- a/src/regexp_bt.c
+++ b/src/regexp_bt.c
@@ -4615,6 +4615,11 @@ regmatch(
 			    if (rex.input == rex.line)
 			    {
 				// backup to last char of previous line
+				if (rex.lnum == 0)
+				{
+				    status = RA_NOMATCH;
+				    break;
+				}
 				--rex.lnum;
 				rex.line = reg_getline(rex.lnum);
 				// Just in case regrepeat() didn't count
diff --git a/src/testdir/test_regexp_utf8.vim b/src/testdir/test_regexp_utf8.vim
index 674eee571d36b..9f5b28816029d 100644
--- a/src/testdir/test_regexp_utf8.vim
+++ b/src/testdir/test_regexp_utf8.vim
@@ -508,7 +508,6 @@ endfunc
 " Check that [[:upper:]] matches for automatic engine
 func Test_match_char_class_upper()
   new
-  let _engine=&regexpengine
 
   " Test 1: [[:upper:]]\{2,\}
   set regexpengine=0
@@ -549,7 +548,7 @@ func Test_match_char_class_upper()
   call assert_equal(4, searchcount().total, 'TEST 3 lower')
 
   " clean up
-  let &regexpengine=_engine
+  set regexpengine=0
   bwipe!
 endfunc
 
@@ -561,4 +560,13 @@ func Test_match_invalid_byte()
   call delete('Xinvalid')
 endfunc
 
+func Test_match_too_complicated()
+  set regexpengine=1
+  exe "vsplit \xeb\xdb\x99"
+  silent! buf \&\zs*\zs*0
+  bwipe!
+  set regexpengine=0
+endfunc
+
+
 " vim: shiftwidth=2 sts=2 expandtab
diff --git a/src/version.c b/src/version.c
index 23f45b5c17c07..809b03f3e5183 100644
--- a/src/version.c
+++ b/src/version.c
@@ -750,6 +750,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    4440,
 /**/
     4439,
 /**/