From 8e2bc47d62d48687f681855d4b086c758ae745c4 Mon Sep 17 00:00:00 2001
From: Denys Vlasenko <vda.linux@googlemail.com>
Date: Wed, 28 Sep 2016 23:02:57 +0200
Subject: [PATCH] ash: [EVAL] Fix use-after-free in dotrap/evalstring

From upstream:

    [EVAL] Fix use-after-free in dotrap/evalstring

    The function dotrap calls evalstring using the stored trap string.
    If evalstring then unsets that exact trap string then we will end
    up using freed memory.

    This patch fixes it by making evalstring always duplicate the string
    before using it.

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
---
 shell/ash.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/shell/ash.c b/shell/ash.c
index f395a16a9..7a7ea1896 100644
--- a/shell/ash.c
+++ b/shell/ash.c
@@ -1459,7 +1459,7 @@ stunalloc(void *p)
  * Like strdup but works with the ash stack.
  */
 static char *
-ststrdup(const char *p)
+sstrdup(const char *p)
 {
 	size_t len = strlen(p) + 1;
 	return memcpy(stalloc(len), p, len);
@@ -2514,7 +2514,7 @@ updatepwd(const char *dir)
 	char *cdcomppath;
 	const char *lim;
 
-	cdcomppath = ststrdup(dir);
+	cdcomppath = sstrdup(dir);
 	STARTSTACKSTR(new);
 	if (*dir != '/') {
 		if (curdir == nullstr)
@@ -6993,7 +6993,7 @@ addfname(const char *name)
 	struct strlist *sp;
 
 	sp = stzalloc(sizeof(*sp));
-	sp->text = ststrdup(name);
+	sp->text = sstrdup(name);
 	*exparg.lastp = sp;
 	exparg.lastp = &sp->next;
 }
@@ -12221,10 +12221,12 @@ evalstring(char *s, int mask)
 	int skip;
 //	int status;
 
+	s = sstrdup(s);
 	setinputstring(s);
 	setstackmark(&smark);
 
 	skip = 0;
+//	status = 0;
 	while ((n = parsecmd(0)) != NODE_EOF) {
 		int i;
 
@@ -12236,7 +12238,9 @@ evalstring(char *s, int mask)
 		if (skip)
 			break;
 	}
+	popstackmark(&smark);
 	popfile();
+	stunalloc(s);
 
 	skip &= mask;
 	evalskip = skip;