From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id B4A57C77B73 for ; Wed, 19 Apr 2023 15:44:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233641AbjDSPo1 convert rfc822-to-8bit (ORCPT ); Wed, 19 Apr 2023 11:44:27 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35434 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233630AbjDSPoJ (ORCPT ); Wed, 19 Apr 2023 11:44:09 -0400 Received: from eu-smtp-delivery-151.mimecast.com (eu-smtp-delivery-151.mimecast.com [185.58.85.151]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 163BEAD2D for ; Wed, 19 Apr 2023 08:43:48 -0700 (PDT) Received: from AcuMS.aculab.com (156.67.243.121 [156.67.243.121]) by relay.mimecast.com with ESMTP with both STARTTLS and AUTH (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384) id uk-mta-66-8kzx0OtrNuu2tXAPYOXeXQ-1; Wed, 19 Apr 2023 16:43:45 +0100 X-MC-Unique: 8kzx0OtrNuu2tXAPYOXeXQ-1 Received: from AcuMS.Aculab.com (10.202.163.6) by AcuMS.aculab.com (10.202.163.6) with Microsoft SMTP Server (TLS) id 15.0.1497.48; Wed, 19 Apr 2023 16:43:45 +0100 Received: from AcuMS.Aculab.com ([::1]) by AcuMS.aculab.com ([::1]) with mapi id 15.00.1497.048; Wed, 19 Apr 2023 16:43:45 +0100 From: David Laight To: 'Brad Spencer' , "netdev@vger.kernel.org" CC: "linux-kernel@vger.kernel.org" Subject: RE: netlink getsockopt() sets only one byte? Thread-Topic: netlink getsockopt() sets only one byte? Thread-Index: AQHZciCdeGKq7qWD/UKbta8L5WEwQ68yxwaw Date: Wed, 19 Apr 2023 15:43:45 +0000 Message-ID: <0c2ea86d55454b55a88db716f967dda4@AcuMS.aculab.com> References: In-Reply-To: Accept-Language: en-GB, en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-ms-exchange-transport-fromentityheader: Hosted x-originating-ip: [10.202.205.107] MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: aculab.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Brad Spencer > Sent: 18 April 2023 18:38 > > Calling getsockopt() on a netlink socket with SOL_NETLINK options that > use type int only sets the first byte of the int value but returns an > optlen equal to sizeof(int), at least on x86_64. > > > The detailed description: > > It looks like netlink_getsockopt() calls put_user() with a char* > pointer, and I think that causes it to copy only one byte from the val > result, despite len being sizeof(int). > > Is this the expected behaviour? The returned size is 4, after all, > and other int-sized socket options (outside of netlink) like > SO_REUSEADDR set all bytes of the int. It will be horribly broken on anything big-endian. David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)