#40858 [Asn]: Thread safety issue in GD

ID: 40858 Updated by: pajoye@php.net Reported By: scottmacvicar at ntlworld dot com Status: Assigned Bug Type: GD related Operating System: RHEL 4 PHP Version: 5.2.1 Assigned To: pajoye New Comment: Yes, we noticed the cacheSetup problem too. One solution is to initialize it in MINIT and destroy it in MSHUTDOWN. I'm working on patch to implement this solution. The first problem looks weird. It defeats the whole purpose of the mutex. I do not have the time now to test. I will give it a try later this week. Previous Comments: ------------------------------------------------------------------------ [2007-03-19 19:13:02] scottmacvicar at ntlworld dot com I should have mentioned, the first patch deals with the segfault so it errors out gracefully. We've got this running on production now. The second patch is an attempt to deal with the race condition that's still present, would probably be simplier to just to call gdFontCacheSetup() again but I'm unsure what the behaviour is of setting up a mutex thats already initialised and then locking it. ------------------------------------------------------------------------ [2007-03-19 18:53:45] tony2001@php.net Assigned to the maintainer. ------------------------------------------------------------------------ [2007-03-19 18:41:15] scottmacvicar at ntlworld dot com Description: ------------ Appears to be still several more thread safety issues in GD, I've not had time to track these all down yet. We're running gdft.c from CVS to fix a few identified issues already. Looking at the code there still appears to be a race condition within the code but it appears to be a pretty tight loop since its not happening as often as before. By looking at gdft.c it looks possible for a fontCache entry to exist during a check, by the time it gets to obtaining the lock the fontCache has been cleared or something similarly evil. The backtrace we've got is: http://public.vbulletin.com/bugs/php/gdcache-bt.txt Patch for first issue to deal with the possibility that a cache entry is null: http://public.vbulletin.com/bugs/php/gdcache-patch-1.txt Potential patch for second issue to deal with gdCacheSetup thread safety: http://public.vbulletin.com/bugs/php/gdcache-patch-2.txt ------------------------------------------------------------------------ -- Edit this bug report at http://bugs.php.net/?id=40858&edit=1