From 3ac1d97a1d9353490493d30088256360435f7731 Mon Sep 17 00:00:00 2001
From: Bram Moolenaar <Bram@vim.org>
Date: Wed, 4 Jan 2023 17:17:54 +0000
Subject: [PATCH] patch 9.0.1145: invalid memory access with recursive
 substitute expression

Problem:    Invalid memory access with recursive substitute expression.
Solution:   Check the return value of vim_regsub().
---
 src/eval.c                      |  5 +++++
 src/testdir/test_substitute.vim | 16 ++++++++++++++++
 2 files changed, 21 insertions(+)

diff --git a/src/eval.c b/src/eval.c
index 2fbd867ab..9ca805061 100644
--- a/src/eval.c
+++ b/src/eval.c
@@ -6969,6 +6969,11 @@ do_string_sub(
 	     * - The text after the match.
 	     */
 	    sublen = vim_regsub(&regmatch, sub, expr, tail, 0, REGSUB_MAGIC);
+	    if (sublen <= 0)
+	    {
+		ga_clear(&ga);
+		break;
+	    }
 	    if (ga_grow(&ga, (int)((end - tail) + sublen -
 			    (regmatch.endp[0] - regmatch.startp[0]))) == FAIL)
 	    {
diff --git a/src/testdir/test_substitute.vim b/src/testdir/test_substitute.vim
index 251322337..4268aab03 100644
--- a/src/testdir/test_substitute.vim
+++ b/src/testdir/test_substitute.vim
@@ -1095,6 +1095,22 @@ func Test_sub_expr_goto_other_file()
   bwipe!
 endfunc
 
+func Test_recursive_expr_substitute()
+  " this was reading invalid memory
+  let lines =<< trim END
+      func Repl(g, n)
+        s
+        r%:s000
+      endfunc
+      next 0
+      let caught = 0
+      s/\%')/\=Repl(0, 0)
+      qall!
+  END
+  call writefile(lines, 'XexprSubst', 'D')
+  call RunVim([], [], '--clean -S XexprSubst')
+endfunc
+
 " Test for the 2-letter and 3-letter :substitute commands
 func Test_substitute_short_cmd()
   new
-- 
2.27.0