Fix CVE-2017-17969:

https://sourceforge.net/p/p7zip/bugs/204/
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2017-17969

Patch copied from Debian.

Subject: Heap-based buffer overflow in 7zip/Compress/ShrinkDecoder.cpp
Origin: vendor, https://sourceforge.net/p/p7zip/bugs/_discuss/thread/0920f369/27d7/attachment/CVE-2017-17969.patch
Forwarded: https://sourceforge.net/p/p7zip/bugs/_discuss/thread/0920f369/#27d7
Bug: https://sourceforge.net/p/p7zip/bugs/204/
Bug-Debian: https://bugs.debian.org/888297
Bug-Debian-Security: https://security-tracker.debian.org/tracker/CVE-2017-17969
Author: Antoine Beaupré <anarcat@debian.org>
Reviewed-by: Salvatore Bonaccorso <carnil@debian.org>
Last-Update: 2018-02-01
Applied-Upstream: 18.00-beta

--- a/CPP/7zip/Compress/ShrinkDecoder.cpp
+++ b/CPP/7zip/Compress/ShrinkDecoder.cpp
@@ -121,8 +121,13 @@ HRESULT CDecoder::CodeReal(ISequentialIn
     {
       _stack[i++] = _suffixes[cur];
       cur = _parents[cur];
+      if (cur >= kNumItems || i >= kNumItems)
+        break;
     }
-    
+
+    if (cur >= kNumItems || i >= kNumItems)
+      break;
+
     _stack[i++] = (Byte)cur;
     lastChar2 = (Byte)cur;
 
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<div class='path'>path: <a href='/guix/log/?id=aeec4a8fc1dce690b5d6aeb163871aca93d50111'>root</a>/<a href='/guix/log/gnu?id=aeec4a8fc1dce690b5d6aeb163871aca93d50111'>gnu</a>/<a href='/guix/log/gnu/packages?id=aeec4a8fc1dce690b5d6aeb163871aca93d50111'>packages</a>/<a href='/guix/log/gnu/packages/patches?id=aeec4a8fc1dce690b5d6aeb163871aca93d50111'>patches</a>/<a href='/guix/log/gnu/packages/patches/groovy-add-exceptionutilsgenerator.patch?id=aeec4a8fc1dce690b5d6aeb163871aca93d50111'>groovy-add-exceptionutilsgenerator.patch</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/gnu/packages/patches/groovy-add-exceptionutilsgenerator.patch?id=aeec4a8fc1dce690b5d6aeb163871aca93d50111&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2018-05-09 13:36:06 +0200'>2018-05-09</span></td><td><a href='/guix/commit/gnu/packages/patches/groovy-add-exceptionutilsgenerator.patch?id=fdc9170bc1d9a57aa9a542c307b15b5b965d2f4b'>gnu: Add java-groovy-bootstrap.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/groovy.scm: New file.
* gnu/packages/patches/groovy-add-exceptionutilsgenerator.patch: New
file.
* gnu/local.mk (GNU_SYSTEM_MODULES, dist_patch_DATA): Add them.
</span></span></td><td>Julien Lepiller</td></tr>