Fixed bug #73156 (segfault on undefined function)

NEWS

@@ -11,6 +11,7 @@ PHP                                                                        NEWS
     password_verify). (Anatol)
   . Fixed bug #73058 (crypt broken when salt is 'too' long). (Anatol)
   . Fixed bug #69579 (Invalid free in extension trait). (John Boehr)
+  . Fixed bug #73156 (segfault on undefined function). (Dmitry)
   . Fixed bug #73163 (PHP hangs if error handler throws while accessing undef
     const in default value). (Nikita)
 

Zend/tests/bug73156.phpt

@@ -0,0 +1,50 @@
+--TEST--
+iBug #73156 (segfault on undefined function)
+--FILE--
+<?php
+class A {
+    public function __call($name, $args) {
+        eval('$args = array(); var_dump(debug_backtrace());');
+    }
+}
+
+$a = new A();
+
+$a->test("test");
+?>
+--EXPECTF--
+array(2) {
+  [0]=>
+  array(3) {
+    ["file"]=>
+    string(%d) "%sbug73156.php"
+    ["line"]=>
+    int(4)
+    ["function"]=>
+    string(4) "eval"
+  }
+  [1]=>
+  array(7) {
+    ["file"]=>
+    string(%d) "%sbug73156.php"
+    ["line"]=>
+    int(10)
+    ["function"]=>
+    string(6) "__call"
+    ["class"]=>
+    string(1) "A"
+    ["object"]=>
+    object(A)#%d (0) {
+    }
+    ["type"]=>
+    string(2) "->"
+    ["args"]=>
+    array(2) {
+      [0]=>
+      string(4) "test"
+      [1]=>
+      array(0) {
+      }
+    }
+  }
+}

Zend/zend_builtin_functions.c

@@ -2211,9 +2211,33 @@ static void debug_backtrace_get_args(zend_execute_data *call, zval *arg_array) /
 		zend_hash_real_init(Z_ARRVAL_P(arg_array), 1);
 		ZEND_HASH_FILL_PACKED(Z_ARRVAL_P(arg_array)) {
 			if (call->func->type == ZEND_USER_FUNCTION) {
-				uint32_t first_extra_arg = call->func->op_array.num_args;
+				uint32_t first_extra_arg = MIN(num_args, call->func->op_array.num_args);
 
-				if (ZEND_CALL_NUM_ARGS(call) > first_extra_arg) {
+				if (UNEXPECTED(call->symbol_table)) {
+					/* In case of attached symbol_table, values on stack may be invalid
+					 * and we have to access them through symbol_table
+					 * See: https://bugs.php.net/bug.php?id=73156
+					 */
+					zend_string *arg_name;
+					zval *arg;
+
+					while (i < first_extra_arg) {
+						arg_name = call->func->op_array.vars[i];
+						arg = zend_hash_find_ind(call->symbol_table, arg_name);
+						if (arg) {
+							if (Z_OPT_REFCOUNTED_P(arg)) {
+								Z_ADDREF_P(arg);
+							}
+							n++;
+							ZEND_HASH_FILL_ADD(arg);
+						} else {
+							zval tmp;
+							ZVAL_UNDEF(&tmp);
+							ZEND_HASH_FILL_ADD(&tmp);
+						}
+						i++;
+					}
+				} else {
 					while (i < first_extra_arg) {
 						if (EXPECTED(Z_TYPE_INFO_P(p) != IS_UNDEF)) {
 							if (Z_OPT_REFCOUNTED_P(p)) {
@@ -2225,8 +2249,8 @@ static void debug_backtrace_get_args(zend_execute_data *call, zval *arg_array) /
 						p++;
 						i++;
 					}
-					p = ZEND_CALL_VAR_NUM(call, call->func->op_array.last_var + call->func->op_array.T);
 				}
+				p = ZEND_CALL_VAR_NUM(call, call->func->op_array.last_var + call->func->op_array.T);
 			}
 
 			while (i < num_args) {