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Fix use-after-free of name in var-var with malicious error handler #12732

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Fix use-after-free of name in var-var with malicious error handler #12732

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19 changes: 19 additions & 0 deletions Zend/tests/oss_fuzz_54325.phpt
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Original file line number Diff line number Diff line change
@@ -0,0 +1,19 @@
--TEST--
oss-fuzz #54325: Fix use-after-free of name in var-var with malicious error handler
--FILE--
<?php
set_error_handler(function ($errno, $errstr) {
var_dump($errstr);
global $x;
$x = new stdClass;
});

// Needs to be non-interned string
$x = strrev('foo');
$$x++;
var_dump($x);
?>
--EXPECT--
string(23) "Undefined variable $oof"
object(stdClass)#2 (0) {
}
7 changes: 7 additions & 0 deletions Zend/zend_vm_def.h
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Original file line number Diff line number Diff line change
Expand Up @@ -1748,13 +1748,20 @@ ZEND_VM_C_LABEL(fetch_this):
} else if (type == BP_VAR_IS || type == BP_VAR_UNSET) {
retval = &EG(uninitialized_zval);
} else {
if (OP1_TYPE == IS_CV) {
/* Keep name alive in case an error handler tries to free it. */
zend_string_addref(name);
}
zend_error(E_WARNING, "Undefined %svariable $%s",
(opline->extended_value & ZEND_FETCH_GLOBAL ? "global " : ""), ZSTR_VAL(name));
if (type == BP_VAR_RW && !EG(exception)) {
retval = zend_hash_update(target_symbol_table, name, &EG(uninitialized_zval));
} else {
retval = &EG(uninitialized_zval);
}
if (OP1_TYPE == IS_CV) {
zend_string_release(name);
}
}
/* GLOBAL or $$name variable may be an INDIRECT pointer to CV */
} else if (Z_TYPE_P(retval) == IS_INDIRECT) {
Expand Down
21 changes: 21 additions & 0 deletions Zend/zend_vm_execute.h
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