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=-13.7 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,UNPARSEABLE_RELAY autolearn=ham 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 F4126C433E6 for ; Wed, 17 Feb 2021 17:26:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id CD34264E33 for ; Wed, 17 Feb 2021 17:26:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234394AbhBQR0j (ORCPT ); Wed, 17 Feb 2021 12:26:39 -0500 Received: from mx2.suse.de ([195.135.220.15]:34706 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230179AbhBQR0h (ORCPT ); Wed, 17 Feb 2021 12:26:37 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 7BA78B7C2; Wed, 17 Feb 2021 17:25:54 +0000 (UTC) Received: from localhost (brahms [local]) by brahms (OpenSMTPD) with ESMTPA id 04828e09; Wed, 17 Feb 2021 17:26:56 +0000 (UTC) From: Luis Henriques To: Amir Goldstein , Jeff Layton , Steve French , Miklos Szeredi , Trond Myklebust , Anna Schumaker , Alexander Viro , "Darrick J. Wong" , Dave Chinner , Greg KH , Nicolas Boichat , Ian Lance Taylor , Luis Lozano Cc: ceph-devel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-cifs@vger.kernel.org, samba-technical@lists.samba.org, linux-fsdevel@vger.kernel.org, linux-nfs@vger.kernel.org, Luis Henriques Subject: [PATCH v3] vfs: fix copy_file_range regression in cross-fs copies Date: Wed, 17 Feb 2021 17:26:54 +0000 Message-Id: <20210217172654.22519-1-lhenriques@suse.de> In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-cifs@vger.kernel.org A regression has been reported by Nicolas Boichat, found while using the copy_file_range syscall to copy a tracefs file. Before commit 5dae222a5ff0 ("vfs: allow copy_file_range to copy across devices") the kernel would return -EXDEV to userspace when trying to copy a file across different filesystems. After this commit, the syscall doesn't fail anymore and instead returns zero (zero bytes copied), as this file's content is generated on-the-fly and thus reports a size of zero. This patch restores some cross-filesystems copy restrictions that existed prior to commit 5dae222a5ff0 ("vfs: allow copy_file_range to copy across devices"). It also introduces a flag (COPY_FILE_SPLICE) that can be used by filesystems calling directly into the vfs copy_file_range to override these restrictions. Right now, only NFS needs to set this flag. Fixes: 5dae222a5ff0 ("vfs: allow copy_file_range to copy across devices") Link: https://lore.kernel.org/linux-fsdevel/20210212044405.4120619-1-drinkcat@chromium.org/ Link: https://lore.kernel.org/linux-fsdevel/CANMq1KDZuxir2LM5jOTm0xx+BnvW=ZmpsG47CyHFJwnw7zSX6Q@mail.gmail.com/ Link: https://lore.kernel.org/linux-fsdevel/20210126135012.1.If45b7cdc3ff707bc1efa17f5366057d60603c45f@changeid/ Reported-by: Nicolas Boichat Signed-off-by: Luis Henriques --- Ok, I've tried to address all the issues and comments. Hopefully this v3 is a bit closer to the final fix. Changes since v2 - do all the required checks earlier, in generic_copy_file_checks(), adding new checks for ->remap_file_range - new COPY_FILE_SPLICE flag - don't remove filesystem's fallback to generic_copy_file_range() - updated commit changelog (and subject) Changes since v1 (after Amir review) - restored do_copy_file_range() helper - return -EOPNOTSUPP if fs doesn't implement CFR - updated commit description fs/nfsd/vfs.c | 3 ++- fs/read_write.c | 44 +++++++++++++++++++++++++++++++++++++++++--- include/linux/fs.h | 7 +++++++ 3 files changed, 50 insertions(+), 4 deletions(-) diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c index 04937e51de56..14e55822c223 100644 --- a/fs/nfsd/vfs.c +++ b/fs/nfsd/vfs.c @@ -578,7 +578,8 @@ ssize_t nfsd_copy_file_range(struct file *src, u64 src_pos, struct file *dst, * limit like this and pipeline multiple COPY requests. */ count = min_t(u64, count, 1 << 22); - return vfs_copy_file_range(src, src_pos, dst, dst_pos, count, 0); + return vfs_copy_file_range(src, src_pos, dst, dst_pos, count, + COPY_FILE_SPLICE); } __be32 nfsd4_vfs_fallocate(struct svc_rqst *rqstp, struct svc_fh *fhp, diff --git a/fs/read_write.c b/fs/read_write.c index 75f764b43418..40a16003fb05 100644 --- a/fs/read_write.c +++ b/fs/read_write.c @@ -1410,6 +1410,33 @@ static ssize_t do_copy_file_range(struct file *file_in, loff_t pos_in, flags); } +/* + * This helper function checks whether copy_file_range can actually be used, + * depending on the source and destination filesystems being the same. + * + * In-kernel callers may set COPY_FILE_SPLICE to override these checks. + */ +static int fops_copy_file_checks(struct file *file_in, struct file *file_out, + unsigned int flags) +{ + if (WARN_ON_ONCE(flags & ~COPY_FILE_SPLICE)) + return -EINVAL; + + if (flags & COPY_FILE_SPLICE) + return 0; + /* + * We got here from userspace, so forbid copies if copy_file_range isn't + * implemented or if we're doing a cross-fs copy. + */ + 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; + + return 0; +} + /* * Performs necessary checks before doing a file copy * @@ -1427,6 +1454,14 @@ static int generic_copy_file_checks(struct file *file_in, loff_t pos_in, loff_t size_in; int ret; + /* Only check f_ops if we're not trying to clone */ + if (!file_in->f_op->remap_file_range || + (file_inode(file_in)->i_sb == file_inode(file_out)->i_sb)) { + ret = fops_copy_file_checks(file_in, file_out, flags); + if (ret) + return ret; + } + ret = generic_file_rw_checks(file_in, file_out); if (ret) return ret; @@ -1474,9 +1509,6 @@ ssize_t vfs_copy_file_range(struct file *file_in, loff_t pos_in, { ssize_t ret; - if (flags != 0) - return -EINVAL; - ret = generic_copy_file_checks(file_in, pos_in, file_out, pos_out, &len, flags); if (unlikely(ret)) @@ -1511,6 +1543,9 @@ ssize_t vfs_copy_file_range(struct file *file_in, loff_t pos_in, ret = cloned; goto done; } + ret = fops_copy_file_checks(file_in, file_out, flags); + if (ret) + return ret; } ret = do_copy_file_range(file_in, pos_in, file_out, pos_out, len, @@ -1543,6 +1578,9 @@ SYSCALL_DEFINE6(copy_file_range, int, fd_in, loff_t __user *, off_in, struct fd f_out; ssize_t ret = -EBADF; + if (flags != 0) + return -EINVAL; + f_in = fdget(fd_in); if (!f_in.file) goto out2; diff --git a/include/linux/fs.h b/include/linux/fs.h index fd47deea7c17..6f604926d955 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -1815,6 +1815,13 @@ struct dir_context { */ #define REMAP_FILE_ADVISORY (REMAP_FILE_CAN_SHORTEN) +/* + * This flag control the behavior of copy_file_range from internal (kernel) + * users. It can be used to override the policy of forbidding copies when + * source and destination filesystems are different. + */ +#define COPY_FILE_SPLICE (1 << 0) + struct iov_iter; struct file_operations {