proper fix for bug #50006

add modify protection to all user array sorts

Author: smalyshev

ext/standard/array.c

@@ -768,6 +768,7 @@ static int php_array_user_key_compare(const void *a, const void *b TSRMLS_DC) /*
 PHP_FUNCTION(uksort)
 {
 	zval *array;
+	int refcount;
 	PHP_ARRAY_CMP_FUNC_VARS;
 
 	PHP_ARRAY_CMP_FUNC_BACKUP();
@@ -777,13 +778,31 @@ PHP_FUNCTION(uksort)
 		return;
 	}
 
+	/* Clear the is_ref flag, so the attemts to modify the array in user
+	 * comaprison function will create a copy of array and won't affect the
+	 * original array. The fact of modification is detected using refcount
+	 * comparison. The result of sorting in such case is undefined and the
+	 * function returns FALSE.
+	 */
+	Z_UNSET_ISREF_P(array);
+	refcount = Z_REFCOUNT_P(array);
+
 	if (zend_hash_sort(Z_ARRVAL_P(array), zend_qsort, php_array_user_key_compare, 0 TSRMLS_CC) == FAILURE) {
-		PHP_ARRAY_CMP_FUNC_RESTORE();
-		RETURN_FALSE;
+		RETVAL_FALSE;
+	} else {
+		if (refcount > Z_REFCOUNT_P(array)) {
+			php_error_docref(NULL TSRMLS_CC, E_WARNING, "Array was modified by the user comparison function");
+			RETVAL_FALSE;
+		} else {
+			RETVAL_TRUE;
+		}
+	}
+
+	if (Z_REFCOUNT_P(array) > 1) {
+		Z_SET_ISREF_P(array);
 	}
 
 	PHP_ARRAY_CMP_FUNC_RESTORE();
-	RETURN_TRUE;
 }
 /* }}} */
 

ext/standard/tests/array/bug50006_1.phpt

@@ -0,0 +1,29 @@
+--TEST--
+Bug #50006 (Segfault caused by uksort()) - usort variant
+--FILE--
+<?php
+
+$data = array(
+    'bar-bazbazbaz.',
+    'bar-bazbazbaz-', 
+    'foo'
+);
+usort($data, 'magic_sort_cmp');
+print_r($data);
+
+function magic_sort_cmp($a, $b) {
+  $a = substr($a, 1);
+  $b = substr($b, 1);
+  if (!$a) return $b ? -1 : 0;
+  if (!$b) return 1;
+  return magic_sort_cmp($a, $b);
+}
+
+?>
+--EXPECTF--
+Array
+(
+    [0] => foo
+    [1] => bar-bazbazbaz-
+    [2] => bar-bazbazbaz.
+)

ext/standard/tests/array/bug50006_2.phpt

@@ -0,0 +1,29 @@
+--TEST--
+Bug #50006 (Segfault caused by uksort()) - uasort variant
+--FILE--
+<?php
+
+$data = array(
+    'bar-bazbazbaz.',
+    'bar-bazbazbaz-', 
+    'foo'
+);
+uasort($data, 'magic_sort_cmp');
+print_r($data);
+
+function magic_sort_cmp($a, $b) {
+  $a = substr($a, 1);
+  $b = substr($b, 1);
+  if (!$a) return $b ? -1 : 0;
+  if (!$b) return 1;
+  return magic_sort_cmp($a, $b);
+}
+
+?>
+--EXPECTF--
+Array
+(
+    [2] => foo
+    [1] => bar-bazbazbaz-
+    [0] => bar-bazbazbaz.
+)