From a4375f3090f3637fae40c5a0e24d2f555250db75 Mon Sep 17 00:00:00 2001
From: Martijn Dekker <martijn@inlv.org>
Date: Mon, 15 Nov 2021 03:18:18 +0100
Subject: [PATCH] Fix crash on unsetting .sh.match

ksh crashed after unsetting .sh.match and then matching a pattern:

$ unset .sh.match
$ [[ bar == ba* ]]
Memory fault

src/cmd/ksh93/sh/init.c: sh_setmatch():
- Do nothing if we cannot get an array pointer to SH_MATCHNOD.
---
 NEWS                    | 2 ++
 src/cmd/ksh93/sh/init.c | 3 +++
 2 files changed, 5 insertions(+)

diff --git a/NEWS b/NEWS
index fff087db3..6ee8a9a33 100644
--- a/NEWS
+++ b/NEWS
@@ -5,6 +5,8 @@ Any uppercase BUG_* names are modernish shell bug IDs.
 
 2021-11-14:
 
+- Fixed: ksh crashed after unsetting .sh.match and then matching a pattern.
+
 - Another test/[ fix: "test \( string1 -a string2 \)" and "test \( string1 -o
   string2 \)" no longer give an incorrect "argument expected" error message.
 
diff --git a/src/cmd/ksh93/sh/init.c b/src/cmd/ksh93/sh/init.c
index 5e263730c..bc89a2f44 100644
--- a/src/cmd/ksh93/sh/init.c
+++ b/src/cmd/ksh93/sh/init.c
@@ -783,6 +783,9 @@ void sh_setmatch(Shell_t *shp,const char *v, int vsize, int nmatch, regoff_t mat
 	unsigned int	savesub = shp->subshell;
 	Namarr_t	*ap = nv_arrayptr(SH_MATCHNOD);
 	Namarr_t	*ap_save = ap;
+	/* do not crash if .sh.match is unset */
+	if(!ap)
+		return;
 	shp->subshell = 0;
 #if !SHOPT_2DMATCH
 	index = 0;