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Fix GH-16188: Handle references after fetching Exception properties #16196

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Fix GH-16188: Handle references after fetching Exception properties #16196

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Handle references after fetching Exception properties
arnaud-lb Oct 3, 2024
87162f8
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arnaud-lb Oct 4, 2024
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34 changes: 34 additions & 0 deletions Zend/tests/gh16188.phpt
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Original file line number Diff line number Diff line change
@@ -0,0 +1,34 @@
--TEST--
GH-16188 (Assertion failure in Zend/zend_exceptions.c)
--FILE--
<?php

$re = new TypeError();
array_walk($re, function (&$item, $key) use (&$re) {
if ($key === "\x00Error\x00previous") {
$item = new Exception();
}
});
printf("getTraceAsString:\n%s\n\n", $re->getTraceAsString());
printf("getPrevious:\n%s\n\n", get_class($re->getPrevious()));
printf("__toString:\n%s\n\n", $re);

?>
==DONE==
--EXPECTF--
getTraceAsString:
#0 {main}

getPrevious:
Exception

__toString:
Exception in %s:%d
Stack trace:%A
#%d {main}

Next TypeError in %s:%d
Stack trace:%A
#%d {main}

==DONE==
16 changes: 12 additions & 4 deletions Zend/zend_exceptions.c
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Original file line number Diff line number Diff line change
Expand Up @@ -115,15 +115,18 @@ void zend_exception_set_previous(zend_object *exception, zend_object *add_previo
ex = &zv;
do {
ancestor = zend_read_property_ex(i_get_exception_base(add_previous), add_previous, ZSTR_KNOWN(ZEND_STR_PREVIOUS), 1, &rv);
ZVAL_DEREF(ancestor);
while (Z_TYPE_P(ancestor) == IS_OBJECT) {
if (Z_OBJ_P(ancestor) == Z_OBJ_P(ex)) {
OBJ_RELEASE(add_previous);
return;
}
ancestor = zend_read_property_ex(i_get_exception_base(Z_OBJ_P(ancestor)), Z_OBJ_P(ancestor), ZSTR_KNOWN(ZEND_STR_PREVIOUS), 1, &rv);
ZVAL_DEREF(ancestor);
}
base_ce = i_get_exception_base(Z_OBJ_P(ex));
previous = zend_read_property_ex(base_ce, Z_OBJ_P(ex), ZSTR_KNOWN(ZEND_STR_PREVIOUS), 1, &rv);
ZVAL_DEREF(previous);
if (Z_TYPE_P(previous) == IS_NULL) {
zend_update_property_ex(base_ce, Z_OBJ_P(ex), ZSTR_KNOWN(ZEND_STR_PREVIOUS), &pv);
GC_DELREF(add_previous);
Expand Down Expand Up @@ -630,6 +633,7 @@ ZEND_METHOD(Exception, getTraceAsString)
RETURN_THROWS();
}

ZVAL_DEREF(trace);
/* Type should be guaranteed by property type. */
ZEND_ASSERT(Z_TYPE_P(trace) == IS_ARRAY);
RETURN_NEW_STR(zend_trace_to_string(Z_ARRVAL_P(trace), /* include_main */ true));
Expand All @@ -639,11 +643,13 @@ ZEND_METHOD(Exception, getTraceAsString)
/* {{{ Return previous Throwable or NULL. */
ZEND_METHOD(Exception, getPrevious)
{
zval rv;
zval *prop, rv;

ZEND_PARSE_PARAMETERS_NONE();

ZVAL_COPY(return_value, GET_PROPERTY_SILENT(ZEND_THIS, ZEND_STR_PREVIOUS));
prop = GET_PROPERTY(ZEND_THIS, ZEND_STR_PREVIOUS);
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@nielsdos nielsdos Oct 3, 2024 •
edited
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Is the change from silent to non-silent intentional?

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Nice catch!

ZVAL_DEREF(prop);
ZVAL_COPY(return_value, prop);
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We have ZVAL_COPY_DEREF, although I see pre-existing places with this pattern too...

} /* }}} */

/* {{{ Obtain the string representation of the Exception object */
Expand Down Expand Up @@ -723,21 +729,23 @@ ZEND_METHOD(Exception, __toString)

Z_PROTECT_RECURSION_P(exception);
exception = GET_PROPERTY(exception, ZEND_STR_PREVIOUS);
if (exception && Z_TYPE_P(exception) == IS_OBJECT && Z_IS_RECURSIVE_P(exception)) {
ZVAL_DEREF(exception);
if (Z_TYPE_P(exception) == IS_OBJECT && Z_IS_RECURSIVE_P(exception)) {
break;
}
}
zend_string_release_ex(fname, 0);

exception = ZEND_THIS;
/* Reset apply counts */
while (exception && Z_TYPE_P(exception) == IS_OBJECT && (base_ce = i_get_exception_base(Z_OBJ_P(exception))) && instanceof_function(Z_OBJCE_P(exception), base_ce)) {
while (Z_TYPE_P(exception) == IS_OBJECT && (base_ce = i_get_exception_base(Z_OBJ_P(exception))) && instanceof_function(Z_OBJCE_P(exception), base_ce)) {
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Speaking of cleanup: we have a similar exception NULL-check on line 670. But that doesn't need to be in this PR.

if (Z_IS_RECURSIVE_P(exception)) {
Z_UNPROTECT_RECURSION_P(exception);
} else {
break;
}
exception = GET_PROPERTY(exception, ZEND_STR_PREVIOUS);
ZVAL_DEREF(exception);
}

exception = ZEND_THIS;
Expand Down
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