#21756 [NoF->Opn]: Accessing $_SERVER['PATH_INFO '] causes intermittent segfault in Apache

ID: 21756 User updated by: php@lost.co.nz Reported By: php@lost.co.nz -Status: No Feedback +Status: Open Bug Type: Reproducible crash Operating System: Linux/Apache (Debian 3.0r1) PHP Version: 4.3.0 New Comment: I have already tried to generate the requested backtrace (as already noted below...), but was unable to get apache to segfault while I was watching. I determined the cause of the bug by comparing access and error logs, looking at the called scripts, and examining points of similarity. The bug was confirmed when, after I wrapped the reads to $_SERVER['PATH_INFO'] (see below) the segfault frequency went from 1-200/day to zero. This was the only change made, which would seem to clinch the deal. Previous Comments: ------------------------------------------------------------------------ [2003-02-04 16:51:06] sniper@php.net No feedback was provided. The bug is being suspended because we assume that you are no longer experiencing the problem. If this is not the case and you are able to provide the information that was requested earlier, please do so and change the status of the bug back to "Open". Thank you. ------------------------------------------------------------------------ [2003-01-20 04:50:25] sniper@php.net Thank you for this bug report. To properly diagnose the problem, we need a backtrace to see what is happening behind the scenes. To find out how to generate a backtrace, please read http://bugs.php.net/bugs-generating-backtrace.php Once you have generated a backtrace, please submit it to this bug report and change the status back to "Open". Thank you for helping us make PHP better. There you can find some info how to use GDB properly. Can you provide a short, COMPLETE and self-contained example script that can be used to reproduce this? It's not much use for us to try guessing unless you don't give us the necessary information.. ------------------------------------------------------------------------ [2003-01-20 04:46:57] php@lost.co.nz Yes, you're right, the include() statement in my toy example should have been wrapped in a pair of braces - the actual code does not contain calls to include() however... I'm sorry I could not provide a backtrace - the thing refused to misbehave when gdb was listening. Prehaps someone who is more familiar with the Apache (1.3) / PHP interface will know where to examine more closely. ------------------------------------------------------------------------ [2003-01-20 00:04:35] sniper@php.net Sounds pretty unlikely for the crash being caused by unset variable/array index. And btw. If you conditionally include() files, then you MUST use { } with the clauses: http://www.php.net/manual/en/function.include.php (Example 12-6) Maybe this caused the crashes? ------------------------------------------------------------------------ [2003-01-19 14:34:35] php@lost.co.nz If the special global $_SERVER['PATH_INFO'] is accessed in scripts on either my test or production server when it is not set (on load of home page usually) it causes Apache to segfault intermittently (like 1/100 page views...). eg, this is what caused me grief: if( $_SERVER['PATH_INFO'] == 'whatever') include( 'whatever_else'); Wrapping in call to 'isset' stopped crashes: if( isset($_SERVER['PATH_INFO']) ) if( $_SERVER['PATH_INFO'] == 'whatever') include( 'whatever_else'); Was really hard to reproduce. In the end I sat at a split screen comparing the error to the access log, second by second. The error log was reporting ~100-300 segfaults a day untill I used the call to isset, when that dropped to zero. (After a fun 6 hours trying to catch it with gdb...) ------------------------------------------------------------------------ -- Edit this bug report at http://bugs.php.net/?id=21756&edit=1