From: =?utf-8?q?Antoine_Beaupr=C3=A9?= <anarcat@debian.org>
Date: Fri, 2 Feb 2018 11:11:41 +0100
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
Reviewed-by: Salvatore Bonaccorso <carnil@debian.org>
Last-Update: 2018-02-01
Applied-Upstream: 18.00-beta

Signed-off-by: André Hentschel <nerv@dawncrow.de>
---
 CPP/7zip/Compress/ShrinkDecoder.cpp | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/CPP/7zip/Compress/ShrinkDecoder.cpp b/CPP/7zip/Compress/ShrinkDecoder.cpp
index 80b7e67..ca37764 100644
--- a/CPP/7zip/Compress/ShrinkDecoder.cpp
+++ b/CPP/7zip/Compress/ShrinkDecoder.cpp
@@ -121,8 +121,13 @@ HRESULT CDecoder::CodeReal(ISequentialInStream *inStream, ISequentialOutStream *
     {
       _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;