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Bug #78409 Segfault when creating instance of ArrayIterator without constructor
Submitted: 2019-08-13 17:00 UTC Modified: 2019-08-15 08:35 UTC
From: nicolas dot grekas+php at gmail dot com Assigned:
Status: Closed Package: Reproducible crash
PHP Version: 7.4.0beta2 OS:
Private report: No CVE-ID: None
 [2019-08-13 17:00 UTC] nicolas dot grekas+php at gmail dot com
Description:
------------
This is related to the new serialization mechanism of PHP 7.4.
I don't have a better reproducer because when I try to isolate the crash, it works...
Here is my reproducer, sorry I don't have a better one for now:
Clone https://github.com/nicolas-grekas/symfony
checkout branch "ve-php74"

Then run
./phpunit src/Symfony/Component/VarExporter/ --do-not-cache-result --filter testExport#6

boom

What the code does is that it:
- uses newInstanceWithoutConstructor to create an ArrayIterator
- clones that instance
- calls __unserialize on the clone instance with a valid payload

The crash happens after these step, when e.g. calling print_r() on the object.
When done "manually", it works. But in the context of the test case, it segfaults. 


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 [2019-08-15 08:35 UTC] nikic@php.net
-Status: Open +Status: Analyzed
 [2019-08-15 08:35 UTC] nikic@php.net
I believe the root cause here is this:

$a = new ArrayObject;
$u = [
    0,
    [],
    [],
];
$a->__unserialize($u);
var_dump($u);

array(3) {
  [0]=>
  int(0)
  [1]=>
  NULL        <-- changed to NULL
  [2]=>
  array(0) {
  }
}
 [2019-08-15 08:40 UTC] nikic@php.net
Automatic comment on behalf of nikita.ppv@gmail.com
Revision: http://git.php.net/?p=php-src.git;a=commit;h=34885408db9e16c48e8c25195c39e0ef758faaaa
Log: Fixed bug #78409
 [2019-08-15 08:40 UTC] nikic@php.net
-Status: Analyzed +Status: Closed
 
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Last updated: Mon Dec 09 04:01:25 2019 UTC