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use-after-free when an error handler removes a failing zlib.inflate filter #24176

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use-after-free when an error handler removes a failing zlib.inflate filter #24176

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30 changes: 30 additions & 0 deletions ext/zlib/tests/zlib_filter_inflate_error_handler_removes_filter.phpt
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Original file line number Diff line number Diff line change
@@ -0,0 +1,30 @@
--TEST--
zlib.inflate filter removed by the error handler of its own notice
--EXTENSIONS--
zlib
--FILE--
<?php
$fp = fopen('php://memory', 'w+');
$filter = stream_filter_append($fp, 'zlib.inflate', STREAM_FILTER_WRITE);
set_error_handler(function (int $errno, string $errstr) use (&$filter) {
echo $errstr, "\n";
var_dump(stream_filter_remove($filter));
return true;
});
var_dump(fwrite($fp, "\xff\xff\xff\xff"));

$fp = fopen('php://memory', 'w+');
fwrite($fp, "\xff\xff\xff\xff");
rewind($fp);
$filter = stream_filter_append($fp, 'zlib.inflate', STREAM_FILTER_READ);
var_dump(fread($fp, 10));
echo "Done\n";
?>
--EXPECT--
fwrite(): zlib: data error
bool(true)
bool(false)
fread(): zlib: data error
bool(true)
bool(false)
Done
3 changes: 2 additions & 1 deletion ext/zlib/zlib_filter.c
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Original file line number Diff line number Diff line change
Expand Up @@ -90,11 +90,12 @@ static php_stream_filter_status_t php_zlib_inflate_filter(
exit_status = PSFS_PASS_ON;
} else if (status != Z_OK && status != Z_BUF_ERROR) {
/* Something bad happened */
php_error_docref(NULL, E_NOTICE, "zlib: %s", zError(status));
php_stream_bucket_delref(bucket);
/* reset these because despite the error the filter may be used again */
data->strm.next_in = data->inbuf;
data->strm.avail_in = 0;
/* Last: an error handler may remove this filter and free data. */
php_error_docref(NULL, E_NOTICE, "zlib: %s", zError(status));
return PSFS_ERR_FATAL;
}
desired -= data->strm.avail_in; /* desired becomes what we consumed this round through */
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