From patchwork Fri May 18 21:57:26 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mark Fasheh X-Patchwork-Id: 10412347 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 0BF5360230 for ; Fri, 18 May 2018 21:57:50 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id EF04D28455 for ; Fri, 18 May 2018 21:57:49 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id E3C6928A80; Fri, 18 May 2018 21:57:49 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.9 required=2.0 tests=BAYES_00, MAILING_LIST_MULTI, RCVD_IN_DNSWL_HI autolearn=unavailable version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 9921528455 for ; Fri, 18 May 2018 21:57:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751846AbeERV5r (ORCPT ); Fri, 18 May 2018 17:57:47 -0400 Received: from mx2.suse.de ([195.135.220.15]:56687 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751009AbeERV5p (ORCPT ); Fri, 18 May 2018 17:57:45 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay1.suse.de (charybdis-ext.suse.de [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id C30B4AE76; Fri, 18 May 2018 21:57:43 +0000 (UTC) From: Mark Fasheh To: linux-fsdevel@vger.kernel.org Cc: linux-btrfs@vger.kernel.org, linux-xfs@vger.kernel.org, "Darrick J . Wong" , Adam Borowski , Mark Fasheh Subject: [PATCH v2 1/2] vfs: allow dedupe of user owned read-only files Date: Fri, 18 May 2018 14:57:26 -0700 Message-Id: <20180518215727.26418-2-mfasheh@suse.de> X-Mailer: git-send-email 2.15.1 In-Reply-To: <20180518215727.26418-1-mfasheh@suse.de> References: <20180518215727.26418-1-mfasheh@suse.de> Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP The permission check in vfs_dedupe_file_range() is too coarse - We only allow dedupe of the destination file if the user is root, or they have the file open for write. This effectively limits a non-root user from deduping their own read-only files. In addition, the write file descriptor that the user is forced to hold open can prevent execution of files. As file data during a dedupe does not change, the behavior is unexpected and this has caused a number of issue reports. For an example, see: https://github.com/markfasheh/duperemove/issues/129 So change the check so we allow dedupe on the target if: - the root or admin is asking for it - the process has write access - the owner of the file is asking for the dedupe - the process could get write access That way users can open read-only and still get dedupe. Signed-off-by: Mark Fasheh --- fs/read_write.c | 17 +++++++++++++++-- 1 file changed, 15 insertions(+), 2 deletions(-) diff --git a/fs/read_write.c b/fs/read_write.c index c4eabbfc90df..cbea4ce58ad1 100644 --- a/fs/read_write.c +++ b/fs/read_write.c @@ -1964,6 +1964,20 @@ int vfs_dedupe_file_range_compare(struct inode *src, loff_t srcoff, } EXPORT_SYMBOL(vfs_dedupe_file_range_compare); +/* Check whether we are allowed to dedupe the destination file */ +static int allow_file_dedupe(struct file *file) +{ + if (capable(CAP_SYS_ADMIN)) + return 1; + if (file->f_mode & FMODE_WRITE) + return 1; + if (uid_eq(current_fsuid(), file_inode(file)->i_uid)) + return 1; + if (!inode_permission(file_inode(file), MAY_WRITE)) + return 1; + return 0; +} + int vfs_dedupe_file_range(struct file *file, struct file_dedupe_range *same) { struct file_dedupe_range_info *info; @@ -1972,7 +1986,6 @@ int vfs_dedupe_file_range(struct file *file, struct file_dedupe_range *same) u64 len; int i; int ret; - bool is_admin = capable(CAP_SYS_ADMIN); u16 count = same->dest_count; struct file *dst_file; loff_t dst_off; @@ -2036,7 +2049,7 @@ int vfs_dedupe_file_range(struct file *file, struct file_dedupe_range *same) if (info->reserved) { info->status = -EINVAL; - } else if (!(is_admin || (dst_file->f_mode & FMODE_WRITE))) { + } else if (!allow_file_dedupe(dst_file)) { info->status = -EINVAL; } else if (file->f_path.mnt != dst_file->f_path.mnt) { info->status = -EXDEV;