[PATCH 1/7] [cmd] Dont overflow parameter length when copying substring

[Ann and Jason Edmeades]

When a length is supplied in a %var:~start,length% syntax make sure
it does not overflow the end of the variable buffer.

[fixes a todo in the tests]
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From 93b469aab15451cc2d5f337dacaaa111dcd1957e Mon Sep 17 00:00:00 2001
From: Jason Edmeades <jason at edmeades.me.uk>
Date: Thu, 25 Oct 2012 21:17:13 +0100
Subject: [PATCH 1/7] [cmd] Dont overflow parameter length when copying
 substring

When a length is supplied in a %var:~start,length% syntax make sure
it does not overflow the end of the variable buffer.

[fixes a todo in the tests]
---
 programs/cmd/tests/test_builtins.cmd.exp |    2 +-
 programs/cmd/wcmdmain.c                  |    1 +
 2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/programs/cmd/tests/test_builtins.cmd.exp b/programs/cmd/tests/test_builtins.cmd.exp
index aeaa14d..8a7e3fa 100644
--- a/programs/cmd/tests/test_builtins.cmd.exp
+++ b/programs/cmd/tests/test_builtins.cmd.exp
@@ -275,7 +275,7 @@ P0S
 q
 qwe
 er
- at todo_wine@'ty'@or_broken@''
+'ty'@or_broken@''
 't'@or_broken@''
 ert at or_broken@qwerty
 e at or_broken@qwerty
diff --git a/programs/cmd/wcmdmain.c b/programs/cmd/wcmdmain.c
index 89c1327..534e5a6 100644
--- a/programs/cmd/wcmdmain.c
+++ b/programs/cmd/wcmdmain.c
@@ -730,6 +730,7 @@ static WCHAR *WCMD_expand_envvar(WCHAR *start,
         else if (copybytes < 0) copybytes = 0;
         WCMD_strsubstW(start, endOfVar + 1, startCopy, copybytes);
       } else {
+        substrlength = min(substrlength, len - (startCopy- thisVarContents + 1));
         WCMD_strsubstW(start, endOfVar + 1, startCopy, substrlength);
       }
 
-- 
1.7.9.5