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List:       kde-devel
Subject:    Re: PATCH: kdelibs/kdecore/kstringhandler.cpp, prevent underflow
From:       Alfons Hoogervorst <alfons () proteus ! demon ! nl>
Date:       2004-01-31 1:54:52
Message-ID: 20040131025452.69282213 () proteus ! demon ! nl
[Download RAW message or body]

Lo Alfons,

On 31-01-04 (Sat) 01:44 +0100 Alfons Hoogervorst
<alfons@proteus.demon.nl> wrote:

| CVS HEAD, but there may be already a fix in the original developer's
| local copy.
| 
| Go to:
| 
| http://better-scm.berlios.de/comparison/comparison.html#web_interface
| 
| Open the "Yes: Vestaweb" link in a new tab.
| 
| Result is 100% CPU usage because rightIdx is decremented without
| checking its lowerbound (0).
| 
| Patch attached adds the lbound check.

Hmng. Not good enough. 

Here's another underflow fix; plus the same checks in the outer loop
condition. 

Surely the orginal developer comes with something better - looking
forward to it. :-)

Bye.

-- 
Ecuación algebraico sin solución posible,
a menos de poseer profundos conocimientos
en matemática - Revueltas (Ocho Por Radio)

["kdelibs.kdecore.kstringhandler.cpp.patch" (text/plain)]

Index: kdecore/kstringhandler.cpp
===================================================================
RCS file: /home/kde/kdelibs/kdecore/kstringhandler.cpp,v
retrieving revision 1.35
diff -u -r1.35 kstringhandler.cpp
--- kdecore/kstringhandler.cpp	29 Jan 2004 11:35:14 -0000	1.35
+++ kdecore/kstringhandler.cpp	31 Jan 2004 01:49:31 -0000
@@ -320,7 +320,9 @@
     return s;
   }
 
-  const unsigned int maxWidth = width - fm.width( '.' ) * 3;
+  const unsigned int maxWidth = width > (uint) fm.width( '.') * 3 
+			      ? width - (uint) fm.width( '.' ) * 3
+			      : width;
   if ( maxWidth <= 0 ) {
     return "...";
   }
@@ -328,11 +330,11 @@
   unsigned int leftIdx = 0, rightIdx = length;
   unsigned int leftWidth = fm.charWidth( s, leftIdx++ );
   unsigned int rightWidth = fm.charWidth( s, --rightIdx );
-  while ( leftWidth + rightWidth < maxWidth ) {
-    while ( leftWidth <= rightWidth && leftWidth + rightWidth < maxWidth ) {
+  while ( leftWidth + rightWidth < maxWidth && leftIdx < length && rightIdx > 0 ) {
+    while ( leftWidth <= rightWidth && leftWidth + rightWidth < maxWidth && leftIdx < length ) {
       leftWidth += fm.charWidth( s, leftIdx++ );
     }
-    while ( rightWidth <= leftWidth && leftWidth + rightWidth < maxWidth ) {
+    while ( rightWidth <= leftWidth && leftWidth + rightWidth < maxWidth && rightIdx > 0 ) {
       rightWidth += fm.charWidth( s, --rightIdx );
     }
   }


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