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=-0.6 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, 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 B863EC433E3 for ; Sat, 16 May 2020 15:37:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 95D1920727 for ; Sat, 16 May 2020 15:37:03 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="RnggIlJM" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727046AbgEPPhC (ORCPT ); Sat, 16 May 2020 11:37:02 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45182 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726695AbgEPPhB (ORCPT ); Sat, 16 May 2020 11:37:01 -0400 Received: from bombadil.infradead.org (bombadil.infradead.org [IPv6:2607:7c80:54:e::133]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9E25CC061A0C; Sat, 16 May 2020 08:37:01 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=TG5YZgmRlXVS7HvhJz7DOFxKZzjqL5DT1HxTsi4ato4=; b=RnggIlJMvxkkVJkInT4pqpaVSA SmN+fQmJr6rXEhoA27zDDtoVe3MfLbqyOGnjbFroFdUEa2bz7T8LXqJhdZ04Kn8zUaw7zqnqucvEE jylJg+5o3OTrPcU/9WnNB5DHJG6s2r/4zP/X7rBAVxQdC6M19CKb7CjJPN7ckvsf+3VEUSWXTjPOs h4KyUBqEslvU/z84GxRvc0uH9xKOs7/moDDDKZUR3/JC6le8XeM7SlwM6eCF1D2ew/AfzjZ81WeGR TID2vSDI6gItLhZe+n8N/K+Igbx6wbsz1MCCu7X4o5NOmt5PKestOUG7qfbgkfaJZ9h4Kw4hb2rBr xNF175SA==; Received: from willy by bombadil.infradead.org with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1jZyrs-000842-U1; Sat, 16 May 2020 15:36:52 +0000 Date: Sat, 16 May 2020 08:36:52 -0700 From: Matthew Wilcox To: David Laight Cc: 'David Howells' , Christoph Hellwig , Marcelo Ricardo Leitner , "linux-nvme@lists.infradead.org" , "linux-kernel@vger.kernel.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" , Jakub Kicinski , "linux-block@vger.kernel.org" , Alexey Kuznetsov , "ceph-devel@vger.kernel.org" , "linux-nfs@vger.kernel.org" , Neil Horman , Hideaki YOSHIFUJI , "netdev@vger.kernel.org" , Vlad Yasevich , Eric Dumazet , Jon Maloy , Ying Xue , "David S. Miller" , "ocfs2-devel@oss.oracle.com" Subject: Re: [Ocfs2-devel] [PATCH 27/33] sctp: export sctp_setsockopt_bindx Message-ID: <20200516153652.GM16070@bombadil.infradead.org> 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> <05d946ae948946158dbfcbc07939b799@AcuMS.aculab.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <05d946ae948946158dbfcbc07939b799@AcuMS.aculab.com> Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Sat, May 16, 2020 at 03:11:40PM +0000, David Laight wrote: > 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. I appreciate your dedication to not publishing the source code to your kernel module, but Christoph's patch series is actually better. It's typesafe rather than passing void pointers around.