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Bug #80186 Segfault when iterating over FFI object
Submitted: 2020-10-04 20:40 UTC Modified: 2020-10-04 20:56 UTC
From: as@php.net Assigned:
Status: Closed Package: Reproducible crash
PHP Version: 8.0Git-2020-10-04 (Git) OS:
Private report: No CVE-ID: None
 [2020-10-04 20:40 UTC] as@php.net
Description:
------------
Currently `zend_fake_get_properties` in `ext/ffi/ffi.c` returns a pointer to const HashTable `zend_empty_array`. Attempting to iterate over this array in userland leads to a segfault because PHP tries to increment `zend_empty_array`'s `nIteratorsCount` which is const memory.

The proposed patch allows objects to return NULL for the `get_properties` handler. In this case, the VM skips the foreach block.

If this approach is acceptable, there are other extensions and call sites[1][2] to fix where `zend_empty_array` leaks into userland.

[1] https://github.com/php/php-src/blob/107962208a19d8b6dc1a190cb25fc37614411e71/ext/com_dotnet/com_handlers.c#L221-L229
[2] https://github.com/protocolbuffers/protobuf/issues/7319


Test script:
---------------
<?php

$ffi = FFI::cdef('');

foreach ($ffi as $_) {
}


Expected result:
----------------
no segfault

Actual result:
--------------
segfault

Patches

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Pull Requests

Pull requests:

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History

AllCommentsChangesGit/SVN commitsRelated reports
 [2020-10-04 20:56 UTC] as@php.net
The following pull request has been associated:

Patch Name: Fix #80186: Prevent segfault when iterating FFI obj props
On GitHub:  https://github.com/php/php-src/pull/6270
Patch:      https://github.com/php/php-src/pull/6270.patch
 [2020-10-04 20:56 UTC] nikic@php.net
zend_empty_array is also used for normal empty arrays [], so it should be possible to make this work...
 [2020-10-09 15:03 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=15443f8af4783ce6ea5362ec5a38a62b69ff8447
Log: Fixed bug #80186
 [2020-10-09 15:03 UTC] nikic@php.net
-Status: Open +Status: Closed
 
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