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 X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 90717C433E0 for ; Sat, 16 May 2020 15:21:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6F1A120767 for ; Sat, 16 May 2020 15:21:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726964AbgEPPVZ convert rfc822-to-8bit (ORCPT ); Sat, 16 May 2020 11:21:25 -0400 Received: from eu-smtp-delivery-151.mimecast.com ([207.82.80.151]:54712 "EHLO eu-smtp-delivery-151.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726615AbgEPPVU (ORCPT ); Sat, 16 May 2020 11:21:20 -0400 Received: from AcuMS.aculab.com (156.67.243.126 [156.67.243.126]) (Using TLS) by relay.mimecast.com with ESMTP id uk-mta-2-M-or8IPqO3ut6gEkeJwgCw-1; Sat, 16 May 2020 16:21:16 +0100 X-MC-Unique: M-or8IPqO3ut6gEkeJwgCw-1 Received: from AcuMS.Aculab.com (fd9f:af1c:a25b:0:43c:695e:880f:8750) by AcuMS.aculab.com (fd9f:af1c:a25b:0:43c:695e:880f:8750) with Microsoft SMTP Server (TLS) id 15.0.1347.2; Sat, 16 May 2020 16:21:15 +0100 Received: from AcuMS.Aculab.com ([fe80::43c:695e:880f:8750]) by AcuMS.aculab.com ([fe80::43c:695e:880f:8750%12]) with mapi id 15.00.1347.000; Sat, 16 May 2020 16:21:15 +0100 From: David Laight To: 'Christoph Hellwig' , David Howells CC: Marcelo Ricardo Leitner , Eric Dumazet , "linux-nvme@lists.infradead.org" , "linux-sctp@vger.kernel.org" , "target-devel@vger.kernel.org" , "linux-afs@lists.infradead.org" , "drbd-dev@lists.linbit.com" , "linux-cifs@vger.kernel.org" , "rds-devel@oss.oracle.com" , "linux-rdma@vger.kernel.org" , "cluster-devel@redhat.com" , Alexey Kuznetsov , "linux-block@vger.kernel.org" , Jakub Kicinski , "ceph-devel@vger.kernel.org" , "linux-nfs@vger.kernel.org" , Neil Horman , Hideaki YOSHIFUJI , "netdev@vger.kernel.org" , Vlad Yasevich , "linux-kernel@vger.kernel.org" , Jon Maloy , Ying Xue , "David S. Miller" , "ocfs2-devel@oss.oracle.com" Subject: RE: [PATCH 27/33] sctp: export sctp_setsockopt_bindx Thread-Topic: [PATCH 27/33] sctp: export sctp_setsockopt_bindx Thread-Index: AQHWKsz+yiOODFVfBEqdWGEpseVc56iq0wgA Date: Sat, 16 May 2020 15:21:15 +0000 Message-ID: References: <20200514062820.GC8564@lst.de> <20200513062649.2100053-1-hch@lst.de> <20200513062649.2100053-28-hch@lst.de> <20200513180058.GB2491@localhost.localdomain> <129070.1589556002@warthog.procyon.org.uk> <20200515152459.GA28995@lst.de> In-Reply-To: <20200515152459.GA28995@lst.de> Accept-Language: en-GB, en-US Content-Language: 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-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org From: Christoph Hellwig > Sent: 15 May 2020 16:25 > On Fri, May 15, 2020 at 04:20:02PM +0100, David Howells wrote: > > Christoph Hellwig wrote: > > > > > > The advantage on using kernel_setsockopt here is that sctp module will > > > > only be loaded if dlm actually creates a SCTP socket. With this > > > > change, sctp will be loaded on setups that may not be actually using > > > > it. It's a quite big module and might expose the system. > > > > > > True. Not that the intent is to kill kernel space callers of setsockopt, > > > as I plan to remove the set_fs address space override used for it. > > > > For getsockopt, does it make sense to have the core kernel load optval/optlen > > into a buffer before calling the protocol driver? Then the driver need not > > see the userspace pointer at all. > > > > Similar could be done for setsockopt - allocate a buffer of the size requested > > by the user inside the kernel and pass it into the driver, then copy the data > > back afterwards. > > I did look into that initially. The problem is that tons of sockopts > entirely ignore optlen and just use a fixed size. So I fear that there > could be tons of breakage if we suddently respect it. Otherwise that > would be a pretty nice way to handle the situation. I'd guess that most application use the correct size for setsockopt(). (Well, apart from using 4 instead of 1.) It is certainly possible to always try to read in 64 bytes regardless of the supplied length, but handle the EFAULT case by shortening the buffer. Historically getsockopt() only wrote the length back. Treating 0 and garbage as (say) 4k and letting the protocol code set a shorten the copy to user might work. All short transfers would want to use an on-stack buffer, so slight oversizes could also be allowed for. OTOH if i did a getsockopt() with too short a length I wouldn't want the kernel to trash my program memory. David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)