Edit report at https://bugs.php.net/bug.php?id=64578&edit=1
ID: 64578
Updated 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
+Status: Closed
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:
Automatic comment on behalf of laruence
Revision:
http://git.php.net/?p=php-src.git;a=commit;h=c96a5bc6be99ff8a4c5dbc1ea3c04d8144bc47a9
Log: Fixed bug #64578 (debug_backtrace in set_error_handler corrupts zend heap:
segfault)
Previous Comments:
------------------------------------------------------------------------
[2013-04-04 05:39:10] larue...@php.net
this is actually non-debug-backtrace related issue.
a more simple reproduce script (5.3 also);
<?php
function x($s) { $resource = fopen("php://input", "r"); $s[$resource] = '2'; };
$y = "1";
x($y);
var_dump($y);
result in an buggy $y there:
Warning: Illegal offset type in /tmp/1.php on line 2
UNKNOWN:0
patch attached.
------------------------------------------------------------------------
[2013-04-04 05:35:56] larue...@php.net
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
------------------------------------------------------------------------
[2013-04-04 03:03:02] larue...@php.net
confirmed, I can reproduce this. looking into it now..
------------------------------------------------------------------------
[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
