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;
>
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<div class='path'>path: <a href='/guix/log/?id=b610e4b9a7d4423603cac1da4f16475fb1e03e83'>root</a>/<a href='/guix/log/tests?id=b610e4b9a7d4423603cac1da4f16475fb1e03e83'>tests</a>/<a href='/guix/log/tests/containers.scm?id=b610e4b9a7d4423603cac1da4f16475fb1e03e83'>containers.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/containers.scm?id=b610e4b9a7d4423603cac1da4f16475fb1e03e83&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2020-10-01 12:51:13 +0200'>2020-10-01</span></td><td><a href='/guix/commit/tests/containers.scm?id=e74818353882f187e5971b5a3a481f17df883dbe'>linux-container: Reset jailed root permissions.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/build/linux-container.scm (mount-file-systems): Add 'chmod' call.
* tests/containers.scm
("call-with-container, mnt namespace, root permissions"): New test.
</span></span></td><td>Jelle Licht</td></tr>
'left'>Author</th></tr>
<tr><td><span title='2020-05-05 13:20:46 +0200'>2020-05-05</span></td><td><a href='/guix/commit/gnu/packages/patches/rust-nettle-disable-vendor.patch?id=098f1d722ba553fddd41a2b9e183fe983b708ff9'>gnu: Add rust-nettle-7.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/crates-io.scm (rust-nettle-7): New variable.
* gnu/packages/patches/rust-nettle-disable-vendor.patch: New file.
* gnu/local.mk: Add it.
</span></span></td><td>Hartmut Goebel</td></tr>