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Date: Tue, 21 Jan 2020 14:39:59 +0800
From: Herbert Xu <herbert@gondor.apana.org.au>
To: Simon Ser <contact@emersion.fr>
Cc: "dash@vger.kernel.org" <dash@vger.kernel.org>
Subject: [PATCH] parser: Catch errors in expandstr
Message-ID: <20200121063959.tel7ty76fkz33xpn@gondor.apana.org.au>
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On Fri, Dec 13, 2019 at 02:51:34PM +0000, Simon Ser wrote:
> Just noticed another dash bug: when setting invalid PS1 values dash
> enters an infinite loop.
> 
> For instance, setting PS1='$(' makes dash print many of these:
> 
>    dash: 1: Syntax error: end of file unexpected (expecting ")")
> 
> It would be nice to fallback to the default PS1 value on error.

This patch fixes it by using the literal value of PS1 should an
error occur during expansion.

Reported-by: Simon Ser <contact@emersion.fr>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Tested-by: Simon Ser <contact@emersion.fr>
Signed-off-by: Ron Yorston <rmy@pobox.com>

diff --git a/src/parser.c b/src/parser.c
index b318b08..201d5bd 100644
--- a/src/parser.c
+++ b/src/parser.c
@@ -1571,28 +1571,43 @@ setprompt(int which)
 const char *
 expandstr(const char *ps)
 {
+	struct jmploc *volatile savehandler;
+	const char *volatile result;
+	volatile int saveprompt;
+	struct jmploc jmploc;
 	union node n;
-	int saveprompt;
+	int err;
 
 	/* XXX Fix (char *) cast. */
 	setinputstring((char *)ps);
 
 	saveprompt = doprompt;
 	doprompt = 0;
+	result = ps;
+	savehandler = handler;
+	if (unlikely(err = setjmp(jmploc.loc)))
+		goto out;
+	handler = &jmploc;
 
 	readtoken1(pgetc_eatbnl(), DQSYNTAX, FAKEEOFMARK, 0);
 
-	doprompt = saveprompt;
-
-	popfile();
-
 	n.narg.type = NARG;
 	n.narg.next = NULL;
 	n.narg.text = wordtext;
 	n.narg.backquote = backquotelist;
 
 	expandarg(&n, NULL, EXP_QUOTED);
-	return stackblock();
+	result = stackblock();
+
+out:
+	handler = savehandler;
+	if (err && exception != EXERROR)
+		longjmp(handler->loc, 1);
+
+	doprompt = saveprompt;
+	popfile();
+
+	return result;
 }
 
 /*