Fix bug #72562 - destroy var_hash properly

Author: smalyshev

ext/session/session.c

@@ -866,7 +866,7 @@ PS_SERIALIZER_DECODE_FUNC(php_serialize) /* {{{ */
 	if (php_var_unserialize(&session_vars, &val, endptr, &var_hash TSRMLS_CC)) {
 		var_push_dtor(&var_hash, &session_vars);
 	}
-	
+
 	PHP_VAR_UNSERIALIZE_DESTROY(var_hash);
 	if (PS(http_session_vars)) {
 		zval_ptr_dtor(&PS(http_session_vars));
@@ -931,6 +931,7 @@ PS_SERIALIZER_DECODE_FUNC(php_binary) /* {{{ */
 		namelen = ((unsigned char)(*p)) & (~PS_BIN_UNDEF);
 
 		if (namelen < 0 || namelen > PS_BIN_MAX || (p + namelen) >= endptr) {
+			PHP_VAR_UNSERIALIZE_DESTROY(var_hash);
 			return FAILURE;
 		}
 

ext/session/tests/bug72562.phpt

@@ -0,0 +1,44 @@
+--TEST--
+Bug #72562: Use After Free in unserialize() with Unexpected Session Deserialization
+--SKIPIF--
+<?php include('skipif.inc'); ?>
+--FILE--
+<?php
+
+ini_set('session.serialize_handler', 'php_binary');
+session_start();
+$sess = "\x1xi:1;\x2y";
+session_decode($sess);
+$uns_1 = '{';
+$out_1[] = unserialize($uns_1);
+unset($out_1);
+$fakezval = ptr2str(1122334455);
+$fakezval .= ptr2str(0);
+$fakezval .= "\x00\x00\x00\x00";
+$fakezval .= "\x01";
+$fakezval .= "\x00";
+$fakezval .= "\x00\x00";
+for ($i = 0; $i < 5; $i++) {
+  $v[$i] = $fakezval.$i;
+}
+$uns_2 = 'R:2;';
+$out_2 = unserialize($uns_2);
+var_dump($out_2);
+
+function ptr2str($ptr)
+{
+	$out = '';
+	for ($i = 0; $i < 8; $i++) {
+		$out .= chr($ptr & 0xff);
+		$ptr >>= 8;
+	}
+	return $out;
+}
+?>
+--EXPECTF--
+Warning: session_decode(): Failed to decode session object. Session has been destroyed in %s/bug72562.php on line %d
+
+Notice: unserialize(): Error at offset 0 of 1 bytes in %s/bug72562.php on line %d
+
+Notice: unserialize(): Error at offset 4 of 4 bytes in %s/bug72562.php on line %d
+bool(false)