From 6c71c5ec4fe8d4adf56f679ef350e33e8454590b Mon Sep 17 00:00:00 2001
From: Martijn Dekker <martijn@inlv.org>
Date: Sat, 16 Jul 2022 05:20:13 +0200
Subject: [PATCH] Properly block .sh.level and .sh.value discipline functions

These now give an "invalid discipline function" error instead of
being silently ignored or crashing the shell.
---
 src/cmd/ksh93/sh/nvdisc.c        |  4 +++-
 src/cmd/ksh93/tests/variables.sh | 14 ++++++++++++++
 2 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/src/cmd/ksh93/sh/nvdisc.c b/src/cmd/ksh93/sh/nvdisc.c
index 6fce69bd5..e543853d9 100644
--- a/src/cmd/ksh93/sh/nvdisc.c
+++ b/src/cmd/ksh93/sh/nvdisc.c
@@ -507,6 +507,8 @@ char *nv_setdisc(register Namval_t* np,register const char *event,Namval_t *acti
 	if (type < 0)
 		return(NIL(char*));
 	/* Handle GET/SET/APPEND/UNSET disc */
+	if(np==SH_VALNOD || np==SH_LEVELNOD)
+		return(0);
 	if(vp && vp->fun.disc->putval!=assign)
 		vp = 0;
 	if(!vp)
@@ -529,7 +531,7 @@ char *nv_setdisc(register Namval_t* np,register const char *event,Namval_t *acti
 		action = vp->disc[type];
 		empty = 0;
 	}
-	else if(action && np!=SH_LEVELNOD)
+	else if(action)
 	{
 		Namdisc_t *dp = (Namdisc_t*)vp->fun.disc;
 		dp->getval = lookup;
diff --git a/src/cmd/ksh93/tests/variables.sh b/src/cmd/ksh93/tests/variables.sh
index f3414e282..1c72af658 100755
--- a/src/cmd/ksh93/tests/variables.sh
+++ b/src/cmd/ksh93/tests/variables.sh
@@ -1401,5 +1401,19 @@ exp=$'0\n1\n1'
 [[ $got == "$exp" ]] || err_exit '${.sh.level} in dot script not correct' \
 	"(expected $(printf %q "$exp"), got $(printf %q "$got"))"
 
+# ======
+# setting a .sh.value or .sh.level discipline makes no sense, but should be an error, not crash the shell
+for v in .sh.value .sh.level
+do
+	for d in get set append
+	do
+		exp=": $v.$d: invalid discipline function"
+		got=$(set +x; { "$SHELL" -c "$v.$d() { .sh.value=foo; }; $v=13; $v+=13; : \${$v}"; } 2>&1)
+		(((e = $?)==1)) && [[ $got == *"$exp" ]] || err_exit "attempt to set $v.get discipline does not fail gracefully" \
+			"(expected status 1 and match of *$(printf %q "$exp")," \
+			"got status $e$( ((e>128)) && print -n /SIG && kill -l "$e") and $(printf %q "$got"))"
+	done
+done
+
 # ======
 exit $((Errors<125?Errors:125))