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 17534C433DF for ; Sat, 16 May 2020 15:11:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id EC3B8207C3 for ; Sat, 16 May 2020 15:11:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726727AbgEPPLp convert rfc822-to-8bit (ORCPT ); Sat, 16 May 2020 11:11:45 -0400 Received: from eu-smtp-delivery-151.mimecast.com ([207.82.80.151]:34984 "EHLO eu-smtp-delivery-151.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727111AbgEPPLp (ORCPT ); Sat, 16 May 2020 11:11:45 -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-182-psAgggZzN62zzCab8iGYhQ-1; Sat, 16 May 2020 16:11:41 +0100 X-MC-Unique: psAgggZzN62zzCab8iGYhQ-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 16:11:40 +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 16:11:40 +0100 From: David Laight To: 'David Howells' , Christoph Hellwig 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: AQHWKsxNyiOODFVfBEqdWGEpseVc56iq0duQ Date: Sat, 16 May 2020 15:11:40 +0000 Message-ID: <05d946ae948946158dbfcbc07939b799@AcuMS.aculab.com> 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> In-Reply-To: <129070.1589556002@warthog.procyon.org.uk> 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: David Howells > Sent: 15 May 2020 16:20 > 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. Yes, it also simplifies all the compat code. And there is a BPF test in setsockopt that also wants to pass on a kernel buffer. I'm willing to sit and write the patch. Quoting from a post I made later on Friday. Basically: This patch sequence (to be written) does the following: Patch 1: Change __sys_setsockopt() to allocate a kernel buffer, copy the data into it then call set_fs(KERNEL_DS). An on-stack buffer (say 64 bytes) will be used for small transfers. Patch 2: The same for __sys_getsockopt(). Patch 3: Compat setsockopt. Patch 4: Compat getsockopt. Patch 5: Remove the user copies from the global socket options code. Patches 6 to n-1; Remove the user copies from the per-protocol code. Patch n: Remove the set_fs(KERNEL_DS) from the entry points. This should be bisectable. David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)