Bug 163398

Summary:	KPixmapCache should remap shared memory when resizing cache
Product:	[Unmaintained] kdelibs	Reporter:	Michael Pyne <mpyne>
Component:	kdeui	Assignee:	kdelibs bugs <kdelibs-bugs-null>
Status:	RESOLVED FIXED
Severity:	normal	CC:	mail
Priority:	NOR
Version First Reported In:	SVN
Target Milestone:	---
Platform:	Compiled Sources
OS:	Linux
Latest Commit:		Version Fixed In:
Sentry Crash Report:

Description Michael Pyne 2008-06-06 22:35:38 UTC

KPixmapCache can be configured to use shared memory using mmap.  When using
shared memory if the underlying file is resized there is a possibility of
causing errors.

If resized smaller then there is no file where earlier there was one.  If
resized larger, the file will be bigger than the area of memory asked for when
mapped, and what happens if the memory corresponding to the new part of the file
is accessed is implementation-defined.

The file can be resized by using the KPixmapCache::setCacheLimit() function
however I have not developed a testcase yet so I'm not sure if I can make it
crash.

Also see bug 160284 where related mmap usage errors led to crashes.

Comment 1 Michael Pyne 2010-05-04 05:29:18 UTC

SVN commit 1122509 by mpyne:

Now that KPixmapCache is not our only resort, make it safer by removing the ability to
schedule a cache resize for later. This is dangerous in regards to setting a higher cache
size since it is possible for the new size to be used before the file and shared memory
segment have actually been resized to match.

Calling the method that resizes the cache also resizes the file/mmap as a side effect, so
don't wait to do it.

BUG:163398


 M  +4 -62     kpixmapcache.cpp  


WebSVN link: http://websvn.kde.org/?view=rev&revision=1122509