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=-7.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,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 2EB15C433E9 for ; Tue, 16 Feb 2021 19:41:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id F348B64E6B for ; Tue, 16 Feb 2021 19:41:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229919AbhBPTlk (ORCPT ); Tue, 16 Feb 2021 14:41:40 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33860 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229699AbhBPTlh (ORCPT ); Tue, 16 Feb 2021 14:41:37 -0500 Received: from mail-il1-x12e.google.com (mail-il1-x12e.google.com [IPv6:2607:f8b0:4864:20::12e]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C6715C061574; Tue, 16 Feb 2021 11:40:56 -0800 (PST) Received: by mail-il1-x12e.google.com with SMTP id o7so9292242ils.2; Tue, 16 Feb 2021 11:40:56 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=ro9/3x4ttJ8TZMSHOr3d/Q45Z3dTqNLwR5slXPST87U=; b=OUJ/l/910KCdePpzHayvzKZRC0M/Gdhnu3Uz86aBD7+K6Zwcn2fb9J2sHesQklCasg KYoOIZigbzv2pCDlS9z7OlomA8EhXvhaiW673nttROfwOEBqZQZJgp9hiW/ucv87McbQ sC/k8WNpQb5meip3P+atycM1oA6ZxQ0zwpIMH5oDZZzCHdHYMSmOsy9PQrTyXED9QuJt L/UxMOhh/cfvz8e4ETrMeEDxNx6J/bTT4cMac0MJ45Jtyk1OPwOVEnD1F4iTILG6YLHs /cCFaPegywzohyW0P0U/5CTgbZ/Kxy4XtERwcuu8EiGo+oVlpC+5WewTe4zbsuyxn1fE ycPQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=ro9/3x4ttJ8TZMSHOr3d/Q45Z3dTqNLwR5slXPST87U=; b=nagztbeWYCKtXYDGJND3IGhoK8PmzTkUClgDvhvvUYTDEfso3d0uHT7LZlT3HvFwyj /+3rA7Xeu4S5itmYqAkYu2erqp5D3gVoJ9Ih2qahy28o83Im0II9efpdpLhD/xfVGl5G ii0eDq6A/ukDy1Gz6vavhE96Qdxbxv4/6Te+ht6MPtw8NBkkzTIGP1W78cU471yml7dO MXuVWW8OInjH0WvIlkzvT/QkMsXKlNocCoOu39Oo9uARqdiCxv03TM43GpCBKl4y/DGw Mu1BeTJqaqaR/T2N0pdScPXH8cMbj7wp6oeEb05ikwRxxrDf8phYxxfAuxI1sV0x9PGk e/xA== X-Gm-Message-State: AOAM530sE48lUyO73B3gX1oeK4CrLCRn9UubsXeO6X1ESqp+r5FxUC5m 23k4QIBy310oZ34ikBOBUODyWkPoFA5bMHPsn5Q= X-Google-Smtp-Source: ABdhPJykHv1NL9d2Ob069nsYUTQZvrsZFtFm1Wv+PGzLoylyDq4bHGLTfJb9OFs9JkSpF6o9TPZDFpUiFQVHuB5tzCA= X-Received: by 2002:a92:2c08:: with SMTP id t8mr17653644ile.72.1613504456127; Tue, 16 Feb 2021 11:40:56 -0800 (PST) MIME-Version: 1.0 References: <20210215154317.8590-1-lhenriques@suse.de> <73ab4951f48d69f0183548c7a82f7ae37e286d1c.camel@hammerspace.com> <92d27397479984b95883197d90318ee76995b42e.camel@hammerspace.com> <87r1lgjm7l.fsf@suse.de> <87blckj75z.fsf@suse.de> <874kibkflh.fsf@suse.de> In-Reply-To: From: Amir Goldstein Date: Tue, 16 Feb 2021 21:40:43 +0200 Message-ID: Subject: Re: [PATCH v2] vfs: prevent copy_file_range to copy across devices To: Steve French Cc: Anna Schumaker , Luis Henriques , Trond Myklebust , "samba-technical@lists.samba.org" , "drinkcat@chromium.org" , "iant@google.com" , "linux-cifs@vger.kernel.org" , "darrick.wong@oracle.com" , "linux-kernel@vger.kernel.org" , "jlayton@kernel.org" , "llozano@chromium.org" , "linux-nfs@vger.kernel.org" , "miklos@szeredi.hu" , "viro@zeniv.linux.org.uk" , "dchinner@redhat.com" , "linux-fsdevel@vger.kernel.org" , "gregkh@linuxfoundation.org" , "sfrench@samba.org" , "ceph-devel@vger.kernel.org" Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: ceph-devel@vger.kernel.org On Tue, Feb 16, 2021 at 9:31 PM Steve French wrote: > > On Tue, Feb 16, 2021 at 1:29 PM Anna Schumaker > wrote: > > > > On Tue, Feb 16, 2021 at 2:22 PM Amir Goldstein wrote: > > > > > > On Tue, Feb 16, 2021 at 8:54 PM Luis Henriques wrote: > > > > > > > > Amir Goldstein writes: > > > > > > > > > On Tue, Feb 16, 2021 at 6:41 PM Luis Henriques wrote: > > > > >> > > > > >> Amir Goldstein writes: > > > > >> > > > > >> >> Ugh. And I guess overlayfs may have a similar problem. > > > > >> > > > > > >> > Not exactly. > > > > >> > Generally speaking, overlayfs should call vfs_copy_file_range() > > > > >> > with the flags it got from layer above, so if called from nfsd it > > > > >> > will allow cross fs copy and when called from syscall it won't. > > > > >> > > > > > >> > There are some corner cases where overlayfs could benefit from > > > > >> > COPY_FILE_SPLICE (e.g. copy from lower file to upper file), but > > > > >> > let's leave those for now. Just leave overlayfs code as is. > > > > >> > > > > >> Got it, thanks for clarifying. > > > > >> > > > > >> >> > This is easy to solve with a flag COPY_FILE_SPLICE (or something) that > > > > >> >> > is internal to kernel users. > > > > >> >> > > > > > >> >> > FWIW, you may want to look at the loop in ovl_copy_up_data() > > > > >> >> > for improvements to nfsd_copy_file_range(). > > > > >> >> > > > > > >> >> > We can move the check out to copy_file_range syscall: > > > > >> >> > > > > > >> >> > if (flags != 0) > > > > >> >> > return -EINVAL; > > > > >> >> > > > > > >> >> > Leave the fallback from all filesystems and check for the > > > > >> >> > COPY_FILE_SPLICE flag inside generic_copy_file_range(). > > > > >> >> > > > > >> >> Ok, the diff bellow is just to make sure I understood your suggestion. > > > > >> >> > > > > >> >> The patch will also need to: > > > > >> >> > > > > >> >> - change nfs and overlayfs calls to vfs_copy_file_range() so that they > > > > >> >> use the new flag. > > > > >> >> > > > > >> >> - check flags in generic_copy_file_checks() to make sure only valid flags > > > > >> >> are used (COPY_FILE_SPLICE at the moment). > > > > >> >> > > > > >> >> Also, where should this flag be defined? include/uapi/linux/fs.h? > > > > >> > > > > > >> > Grep for REMAP_FILE_ > > > > >> > Same header file, same Documentation rst file. > > > > >> > > > > > >> >> > > > > >> >> Cheers, > > > > >> >> -- > > > > >> >> Luis > > > > >> >> > > > > >> >> diff --git a/fs/read_write.c b/fs/read_write.c > > > > >> >> index 75f764b43418..341d315d2a96 100644 > > > > >> >> --- a/fs/read_write.c > > > > >> >> +++ b/fs/read_write.c > > > > >> >> @@ -1383,6 +1383,13 @@ ssize_t generic_copy_file_range(struct file *file_in, loff_t pos_in, > > > > >> >> struct file *file_out, loff_t pos_out, > > > > >> >> size_t len, unsigned int flags) > > > > >> >> { > > > > >> >> + if (!(flags & COPY_FILE_SPLICE)) { > > > > >> >> + if (!file_out->f_op->copy_file_range) > > > > >> >> + return -EOPNOTSUPP; > > > > >> >> + else if (file_out->f_op->copy_file_range != > > > > >> >> + file_in->f_op->copy_file_range) > > > > >> >> + return -EXDEV; > > > > >> >> + } > > > > >> > > > > > >> > That looks strange, because you are duplicating the logic in > > > > >> > do_copy_file_range(). Maybe better: > > > > >> > > > > > >> > if (WARN_ON_ONCE(flags & ~COPY_FILE_SPLICE)) > > > > >> > return -EINVAL; > > > > >> > if (flags & COPY_FILE_SPLICE) > > > > >> > return do_splice_direct(file_in, &pos_in, file_out, &pos_out, > > > > >> > len > MAX_RW_COUNT ? MAX_RW_COUNT : len, 0); > > > > >> > > > > >> My initial reasoning for duplicating the logic in do_copy_file_range() was > > > > >> to allow the generic_copy_file_range() callers to be left unmodified and > > > > >> allow the filesystems to default to this implementation. > > > > >> > > > > >> With this change, I guess that the calls to generic_copy_file_range() from > > > > >> the different filesystems can be dropped, as in my initial patch, as they > > > > >> will always get -EINVAL. The other option would be to set the > > > > >> COPY_FILE_SPLICE flag in those calls, but that would get us back to the > > > > >> problem we're trying to solve. > > > > > > > > > > I don't understand the problem. > > > > > > > > > > What exactly is wrong with the code I suggested? > > > > > Why should any filesystem be changed? > > > > > > > > > > Maybe I am missing something. > > > > > > > > Ok, I have to do a full brain reboot and start all over. > > > > > > > > Before that, I picked the code you suggested and tested it. I've mounted > > > > a cephfs filesystem and used xfs_io to execute a 'copy_range' command > > > > using /sys/kernel/debug/sched_features as source. The result was a > > > > 0-sized file in cephfs. And the reason is thevfs_copy_file_range() > > > > early exit in: > > > > > > > > if (len == 0) > > > > return 0; > > > > > > > > 'len' is set in generic_copy_file_checks(). > > > > > > Good point.. I guess we will need to do all the checks earlier in > > > generic_copy_file_checks() including the logic of: > > > > > > if (file_in->f_op->remap_file_range && > > > file_inode(file_in)->i_sb == file_inode(file_out)->i_sb) > > > > > > > > > > > > > > This means that we're not solving the original problem anymore (probably > > > > since v1 of this patch, haven't checked). > > > > > > > > Also, re-reading Trond's emails, I read: "... also disallowing the copy > > > > from, say, an XFS formatted partition to an ext4 partition". Isn't that > > > > *exactly* what we're trying to do here? I.e. _prevent_ these copies from > > > > happening so that tracefs files can't be CFR'ed? > > > > > > > > > > We want to address the report which means calls coming from > > > copy_file_range() syscall. > > > > > > Trond's use case is vfs_copy_file_range() coming from nfsd. > > > When he writes about copy from XFS to ext4, he means an > > > NFS client is issuing server side copy (on same or different NFS mounts) > > > and the NFS server is executing nfsd_copy_file_range() on a source > > > file that happens to be on XFS and destination happens to be on ext4. > > > > NFS also supports a server-to-server copy where the destination server > > mounts the source server and reads the data to be copied. Please don't > > break that either :) > As long as the copy is via nfsd_copy_file_range() and not from the syscall it should not regress. > This is a case we will eventually need to support for cifs (SMB3) as well. > samba already does server side copy very well without needing any support from the kernel. nfsd also doesn't *need* to use vfs_copy_file_range() it can use kernel APIs like the loop in ovl_copy_up_data(). But it does, so we should not regress it. samba/nfsd can try to use copy_file_range() and it will work if the source/target fs support it. Otherwise, the server can perfectly well do the copy via other available interfaces, just like userspace copy tools. Thanks, Amir.