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Fix GH-13827: Null pointer access of type 'zval' in phpdbg_frame #13831

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Fix GH-13827: Null pointer access of type 'zval' in phpdbg_frame #13831

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13 changes: 11 additions & 2 deletions sapi/phpdbg/phpdbg_frame.c
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Original file line number Diff line number Diff line change
Expand Up @@ -274,7 +274,8 @@ void phpdbg_dump_backtrace(size_t num) /* {{{ */
Z_STR(startfile) = zend_string_init(startfilename, strlen(startfilename), 0);

zend_hash_internal_pointer_reset_ex(Z_ARRVAL(zbacktrace), &position);
tmp = zend_hash_get_current_data_ex(Z_ARRVAL(zbacktrace), &position);

zval *function_name = NULL;
while ((tmp = zend_hash_get_current_data_ex(Z_ARRVAL(zbacktrace), &position))) {
if (file) { /* userland */
phpdbg_out("frame #%d: ", i);
Expand All @@ -289,10 +290,18 @@ void phpdbg_dump_backtrace(size_t num) /* {{{ */

file = zend_hash_str_find(Z_ARRVAL_P(tmp), ZEND_STRL("file"));
line = zend_hash_str_find(Z_ARRVAL_P(tmp), ZEND_STRL("line"));
function_name = zend_hash_find(Z_ARRVAL_P(tmp), ZSTR_KNOWN(ZEND_STR_FUNCTION));

zend_hash_move_forward_ex(Z_ARRVAL(zbacktrace), &position);
}

phpdbg_writeln("frame #%d: {main} at %s:"ZEND_LONG_FMT, i, Z_STRVAL_P(file), Z_LVAL_P(line));
/* This is possible for fibers' start closure for example, which have a frame that doesn't contain the info
* of which location stated the fiber if that stack frame is already torn down. same behaviour with debug_backtrace(). */
if (file == NULL) {
phpdbg_writeln(" => %s (internal function)", Z_STRVAL_P(function_name));
} else {
phpdbg_writeln("frame #%d: {main} at %s:"ZEND_LONG_FMT, i, Z_STRVAL_P(file), Z_LVAL_P(line));
}

zval_ptr_dtor_nogc(&zbacktrace);
zend_string_release(Z_STR(startfile));
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30 changes: 30 additions & 0 deletions sapi/phpdbg/tests/gh13827.phpt
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Original file line number Diff line number Diff line change
@@ -0,0 +1,30 @@
--TEST--
GH-13827 (Null pointer access of type 'zval' in phpdbg_frame)
--FILE--
<?php

$fiber = new Fiber(function () {
$fiber = Fiber::getCurrent();

Fiber::suspend();
});

$fiber->start();

$fiber = null;
gc_collect_cycles();

?>
--PHPDBG--
r
t
q
--EXPECTF--
[Successful compilation of %s]
prompt> [Uncaught GracefulExit in on line 0: ]
>00006: Fiber::suspend();
00007: });
00008:
prompt> frame #0: {closure}() at %s:6
=> {closure} (internal function)
prompt>