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=-14.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_GIT 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 2F713C2D0A3 for ; Mon, 9 Nov 2020 13:49:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id DBB87206ED for ; Mon, 9 Nov 2020 13:49:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1604929766; bh=nrH2hU3hwpPBEY5fbZQPXXDgNeFP4A+Z4c6DQ1q30xI=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=aPQ1zdn4F2Et1s95KCq4QoY8LcP6jQfmqGnsfFDFOOCCn8K9Mw+ys7siMK6DtR2xn Zr1qGshQW5ZM7yBKDV+7WDCUI85b9t6p4rxdepA2w3mb99xdfzi+KwTd6ckVAmDMk/ sXt3zN/5pGjZdQPpvCo/yisbNrVyp6XinO4UlGik= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729970AbgKINtJ (ORCPT ); Mon, 9 Nov 2020 08:49:09 -0500 Received: from mail.kernel.org ([198.145.29.99]:51118 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729817AbgKIM4Z (ORCPT ); Mon, 9 Nov 2020 07:56:25 -0500 Received: from localhost (83-86-74-64.cable.dynamic.v4.ziggo.nl [83.86.74.64]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id E8C63208FE; Mon, 9 Nov 2020 12:56:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1604926575; bh=nrH2hU3hwpPBEY5fbZQPXXDgNeFP4A+Z4c6DQ1q30xI=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=PyJ4XFJS2GQLF0gf+5yRe2uartTHZupAOR1iXWc++No5QyQcdNGBf+DvGWVv1xZTZ QJEre2NsJ8yCX/S8wZwqc5BMRNuMpPk5LY59GPrugKzPBl+i1s81Ricnb5airBmDPg Dk3pVzSJEbs3oWCA4aaqrcOOi4e9+B2bev75rSbo= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Michael Halcrow , Joe Richey , Eric Biggers Subject: [PATCH 4.4 09/86] fscrypt: return -EXDEV for incompatible rename or link into encrypted dir Date: Mon, 9 Nov 2020 13:54:16 +0100 Message-Id: <20201109125021.309070153@linuxfoundation.org> X-Mailer: git-send-email 2.29.2 In-Reply-To: <20201109125020.852643676@linuxfoundation.org> References: <20201109125020.852643676@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Eric Biggers commit f5e55e777cc93eae1416f0fa4908e8846b6d7825 upstream. Currently, trying to rename or link a regular file, directory, or symlink into an encrypted directory fails with EPERM when the source file is unencrypted or is encrypted with a different encryption policy, and is on the same mountpoint. It is correct for the operation to fail, but the choice of EPERM breaks tools like 'mv' that know to copy rather than rename if they see EXDEV, but don't know what to do with EPERM. Our original motivation for EPERM was to encourage users to securely handle their data. Encrypting files by "moving" them into an encrypted directory can be insecure because the unencrypted data may remain in free space on disk, where it can later be recovered by an attacker. It's much better to encrypt the data from the start, or at least try to securely delete the source data e.g. using the 'shred' program. However, the current behavior hasn't been effective at achieving its goal because users tend to be confused, hack around it, and complain; see e.g. https://github.com/google/fscrypt/issues/76. And in some cases it's actually inconsistent or unnecessary. For example, 'mv'-ing files between differently encrypted directories doesn't work even in cases where it can be secure, such as when in userspace the same passphrase protects both directories. Yet, you *can* already 'mv' unencrypted files into an encrypted directory if the source files are on a different mountpoint, even though doing so is often insecure. There are probably better ways to teach users to securely handle their files. For example, the 'fscrypt' userspace tool could provide a command that migrates unencrypted files into an encrypted directory, acting like 'shred' on the source files and providing appropriate warnings depending on the type of the source filesystem and disk. Receiving errors on unimportant files might also force some users to disable encryption, thus making the behavior counterproductive. It's desirable to make encryption as unobtrusive as possible. Therefore, change the error code from EPERM to EXDEV so that tools looking for EXDEV will fall back to a copy. This, of course, doesn't prevent users from still doing the right things to securely manage their files. Note that this also matches the behavior when a file is renamed between two project quota hierarchies; so there's precedent for using EXDEV for things other than mountpoints. xfstests generic/398 will require an update with this change. [Rewritten from an earlier patch series by Michael Halcrow.] Cc: Michael Halcrow Cc: Joe Richey Signed-off-by: Eric Biggers Signed-off-by: Greg Kroah-Hartman --- fs/ext4/namei.c | 6 +++--- fs/f2fs/namei.c | 6 +++--- 2 files changed, 6 insertions(+), 6 deletions(-) --- a/fs/ext4/namei.c +++ b/fs/ext4/namei.c @@ -3218,7 +3218,7 @@ static int ext4_link(struct dentry *old_ return -EMLINK; if (ext4_encrypted_inode(dir) && !ext4_is_child_context_consistent_with_parent(dir, inode)) - return -EPERM; + return -EXDEV; err = dquot_initialize(dir); if (err) return err; @@ -3537,7 +3537,7 @@ static int ext4_rename(struct inode *old ext4_encrypted_inode(new.dir) && !ext4_is_child_context_consistent_with_parent(new.dir, old.inode)) { - retval = -EPERM; + retval = -EXDEV; goto end_rename; } @@ -3718,7 +3718,7 @@ static int ext4_cross_rename(struct inod old.inode) || !ext4_is_child_context_consistent_with_parent(old_dir, new.inode))) - return -EPERM; + return -EXDEV; retval = dquot_initialize(old.dir); if (retval) --- a/fs/f2fs/namei.c +++ b/fs/f2fs/namei.c @@ -169,7 +169,7 @@ static int f2fs_link(struct dentry *old_ if (f2fs_encrypted_inode(dir) && !f2fs_is_child_context_consistent_with_parent(dir, inode)) - return -EPERM; + return -EXDEV; f2fs_balance_fs(sbi); @@ -597,7 +597,7 @@ static int f2fs_rename(struct inode *old if ((old_dir != new_dir) && f2fs_encrypted_inode(new_dir) && !f2fs_is_child_context_consistent_with_parent(new_dir, old_inode)) { - err = -EPERM; + err = -EXDEV; goto out; } @@ -758,7 +758,7 @@ static int f2fs_cross_rename(struct inod old_inode) || !f2fs_is_child_context_consistent_with_parent(old_dir, new_inode))) - return -EPERM; + return -EXDEV; f2fs_balance_fs(sbi);