Fix incorrect zval type_flags in preg_replace_callback_array() for immutable arrays

The ZVAL_ARR macro always set the zval type_info to IS_ARRAY_EX, even if the
hash table is immutable. Since in preg_replace_callback_array() we can return
the passed array directly, and that passed array can be immutable, we need to
reset the type_flags to keep the VM from performing ref-counting on the array.

Fixes phpGH-10968
Closes phpGH-10970

Author: iluuu1994

NEWS

@@ -9,6 +9,9 @@ PHP                                                                        NEWS
   . Fixed bug #80602 (Segfault when using DOMChildNode::before()).
     (Nathan Freeman)
 
+- PCRE:
+  . Fixed bug GH-10968 (Segfault in preg_replace_callback_array()). (ilutov)
+
 13 Apr 2023, PHP 8.1.18
 
 - Core:

ext/pcre/php_pcre.c

@@ -2479,7 +2479,12 @@ PHP_FUNCTION(preg_replace_callback_array)
 	}
 
 	if (subject_ht) {
-		RETURN_ARR(subject_ht);
+		RETVAL_ARR(subject_ht);
+		// Unset the type_flags of immutable arrays to prevent the VM from performing refcounting
+		if (GC_FLAGS(subject_ht) & IS_ARRAY_IMMUTABLE) {
+			Z_TYPE_FLAGS_P(return_value) = 0;
+		}
+		return;
 	} else {
 		RETURN_STR(subject_str);
 	}

ext/pcre/tests/gh10968.phpt

@@ -0,0 +1,11 @@
+--TEST--
+GH-10968: preg_replace_callback_array() segmentation fault
+--FILE--
+<?php
+var_dump(preg_replace_callback_array([], []));
+var_dump(preg_replace_callback_array([], ''));
+?>
+--EXPECT--
+array(0) {
+}
+string(0) ""