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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usage of sparse files that are substituted such as
Guile object files (ELF files).  As of Guile 3.0.9, .go files are sparse
due to ELF sections being aligned on 64 KiB boundaries.

This reduces disk usage reported by “du -sh” by 9% for the ‘guix’
package, by 23% for ‘guile’, and by 35% for ‘guile-git’.

* guix/store/deduplication.scm (hole-size, find-holes): New procedures.
(tee)[seekable?]: New variable.
[read!]: Add case when SEEKABLE? is true.
* tests/store-deduplication.scm (cartesian-product): New procedure.
("copy-file/deduplicate, sparse files (holes: ~a/~a/~a)"): New test set.

Change-Id: Iad2ab7830dcb1220e2026f4a127a6c718afa8964
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2022-12-10 10:56:48 +0100'>2022-12-10</span></td><td><a href='/guix/commit/tests/store-deduplication.scm?id=b129026e2e242e9068158ae6e6fcd8d7c5ea092e'>deduplicate: Use 'sendfile' for small file copies.</a><span class='msg-avail'>...<span class='msg-tooltip'>* guix/store/deduplication.scm (dump-file/deduplicate): Use 'sendfile'
instead of 'dump-port'.
* tests/store-deduplication.scm ("copy-file/deduplicate, below %deduplication-minimum-size"):
New test.
</span></span></td><td>Ludovic Courtès</td></tr>