Fix out-of-bounds read in c_substitute():

http://seclists.org/oss-sec/2016/q4/612

Patch copied from upstream source repository:

https://github.com/tcsh-org/tcsh/commit/6a542dc4fb2ba26518a47e9b3a9bcd6a91b94596

From 6a542dc4fb2ba26518a47e9b3a9bcd6a91b94596 Mon Sep 17 00:00:00 2001
From: christos <christos>
Date: Fri, 2 Dec 2016 16:59:28 +0000
Subject: [PATCH] Fix out of bounds read (Brooks Davis) (reproduce by starting
 tcsh and hitting tab at the prompt)

---
 ed.chared.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/ed.chared.c b/ed.chared.c
index 1277e53..310393e 100644
--- ed.chared.c
+++ ed.chared.c
@@ -750,7 +750,7 @@ c_substitute(void)
     /*
      * If we found a history character, go expand it.
      */
-    if (HIST != '\0' && *p == HIST)
+    if (p >= InputBuf && HIST != '\0' && *p == HIST)
 	nr_exp = c_excl(p);
     else
         nr_exp = 0;
s='sub'>Wojtek's customized Guix</td><td class='sub right'></td></tr></table>
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<div class='path'>path: <a href='/guix/log/?id=d27f072961d166abe21e844c646816304a73d518'>root</a>/<a href='/guix/log/tests?id=d27f072961d166abe21e844c646816304a73d518'>tests</a>/<a href='/guix/log/tests/cve.scm?id=d27f072961d166abe21e844c646816304a73d518'>cve.scm</a></div><div class='content'><table class='list nowrap'><tr class='nohover'><th class='left'>Age</th><th class='left'>Commit message (<a href='/guix/log/tests/cve.scm?id=d27f072961d166abe21e844c646816304a73d518&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2019-10-23 16:40:17 +0200'>2019-10-23</span></td><td><a href='/guix/commit/tests/cve.scm?id=74afaa37d5dec1a9d1b83951529ba69d8947fb07'>cve: Rewrite to read the JSON feed instead of the XML feed.</a><span class='msg-avail'>...<span class='msg-tooltip'>The XML feed was discontinued on Oct. 16th, 2019:

  &lt;https://nvd.nist.gov/General/News/XML-Vulnerability-Feed-Retirement-Phase-3&gt;

* guix/cve.scm (string-&gt;date*): New procedure.
(&lt;cve-item&gt;, &lt;cve&gt;, &lt;cve-reference&gt;): New record types.
(cpe-match-&gt;cve-configuration, configuration-data-&gt;cve-configurations)
(json-&gt;cve-items, version-matches?): New procedures.
(yearly-feed-uri): Change URL to refer to JSON feed.
(cpe-&gt;product-alist, %parse-vulnerability-feed)
(xml-&gt;vulnerabilities): Remove.
(cve-configuration-&gt;package-list, merge-package-lists)
(cve-item-&gt;vulnerability, json-&gt;vulnerabilities): New procedures.
(write-cache): Use 'json-&gt;vulnerabilities' instead of
'xml-&gt;vulnerabilities', and remove 'parameterize'.
(vulnerabilities-&gt;lookup-proc): Use 'version-matches?' when VERSION is
true.
* tests/cve.scm (%sample): Use 'tests/cve-sample.json'.
(%expected-vulnerabilities): Rewrite accordingly.
("json-&gt;cve-items", "cve-item-published-date")
("json-&gt;vulnerabilities"): New tests.
("xml-&gt;vulnerabilities"): Remove.
("vulnerabilities-&gt;lookup-proc"): Adjust to new vulnerabilities.
* tests/cve-sample.json: New file.
* tests/cve-sample.xml: Remove.
* Makefile.am (EXTRA_DIST): Adjust accordingly.
* doc/guix.texi (Invoking guix lint): Update nist.gov URLs.
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2019-10-20 23:26:50 +0200'>2019-10-20</span></td><td><a href='/guix/commit/tests/cve.scm?id=79c03e55e26d88c8d327daced02367abe7f17f91'>tests: Avoid now-deprecated 'make-struct'.</a><span class='msg-avail'>...<span class='msg-tooltip'>* tests/cve.scm (vulnerability): Use 'make-struct/no-tail' instead of
'make-struct', which is deprecated.
* tests/lint.scm ("cve: one vulnerability")
("cve: one patched vulnerability")
("cve: known safe from vulnerability")
("cve: vulnerability fixed in replacement version")
("cve: patched vulnerability in replacement"): Likewise.
</span></span></td><td>Ludovic Courtès</td></tr>