Edit report at https://bugs.php.net/bug.php?id=64578&edit=1
ID: 64578
Patch added by: larue...@php.net
Reported by: emiel dot mols at gmail dot com
Summary: debug_backtrace in set_error_handler corrupts zend
heap: segfault
Status: Verified
Type: Bug
Package: Reproducible crash
Operating System: Irrelevant
PHP Version: 5.5Git-2013-04-03 (snap)
Block user comment: N
Private report: N
New Comment:
The following patch has been added/updated:
Patch Name: bug64578.patch
Revision: 1365053756
URL:
https://bugs.php.net/patch-display.php?bug=64578&patch=bug64578.patch&revision=1365053756
Previous Comments:
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[2013-04-04 03:03:02] larue...@php.net
confirmed, I can reproduce this. looking into it now..
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[2013-04-03 19:44:37] emiel dot mols at gmail dot com
Description:
------------
So I thought the other day it might be convenient to grab a stack trace in, you
know, the place errors are handled. Apparently, PHP thinks this is a terrible
idea.
The exact cause is unclear, but I've managed to create a decently small test
case that segfaults both on Debian PHP 5.4.4 and Darwin PHP 5.5 nightly.
In the attached test script, the call to x() should generate an error, because
accessing a string as associative array is forbidden.
- the segfault occurs in native _zend_mm_free_int
- only able to replicate when there's a function call on the PHP stack
- it appears debug_backtrace is only corrupting the stack -- the call to
print_r() initiates the segfault.
- i've seen $y change every access (eg containing random other variables, or
just random heap garbage).
- in narrowing down the specific case, I've also often seen messages along the
lines of "mm stack corrupt"
Core dumps can be found at:
- Debian: http://db.tt/aA5wAx7a (16MB)
- Darwin: http://db.tt/gxZrP8Pa (400MB)
Test script:
---------------
<?php
set_error_handler(function() { debug_backtrace(); });
function x($s) { $s['a'] = 1; };
$y = '1';
x($y);
print_r($y);
Expected result:
----------------
Being able to use debug_backtrace() in error handlers.
Actual result:
--------------
A corrupt heap, resulting in a freaking segfault.
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Edit this bug report at https://bugs.php.net/bug.php?id=64578&edit=1
