From patchwork Tue Jul 13 11:13:38 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Christian Brauner X-Patchwork-Id: 12373729 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=-19.7 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,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 BAD2FC11F66 for ; Tue, 13 Jul 2021 11:16:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A42976127C for ; Tue, 13 Jul 2021 11:16:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236025AbhGMLTn (ORCPT ); Tue, 13 Jul 2021 07:19:43 -0400 Received: from mail.kernel.org ([198.145.29.99]:47530 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235920AbhGMLTn (ORCPT ); Tue, 13 Jul 2021 07:19:43 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id A26BD61164; Tue, 13 Jul 2021 11:16:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1626175013; bh=RvWedfsmMrpM+9NCCB794l2U7Q955yR624q1FcsFZE0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=g+SKauGSqndxS6gPsPnGmiURh8/p9J5mp77sc1Gw3bEEuKC3jPYi85CXpjewQOCQZ rZTg24VvauNvHAoWmpmI0pISJCHjTCmEQvXd6v7a3khlrddGlX62Ix7hx/gzuaNGTR 5isXtWsfrS19tRLqb+XOEQWyg84vlReCjEnjot07vWm0aALYKGFd3eApBuu/THSVXR Dd4FrIl9folvr5DrO1JvTUbOXvYKwFGXfwp7xOblH5MZ0k7HfP0AO9M8nPeIOYOnDT kFF+iPvnYjjQ3RDJHgkYSqgfl9vp/mczzGEzWOpwthi5VKoyOEJN7HfpqpAYTdVMMJ UHAIJivZ51xKA== From: Christian Brauner To: Christoph Hellwig , Chris Mason , Josef Bacik , David Sterba , Al Viro Cc: linux-btrfs@vger.kernel.org, linux-fsdevel@vger.kernel.org, Christian Brauner , Christoph Hellwig Subject: [PATCH 18/24] btrfs/ioctl: relax restrictions for BTRFS_IOC_SNAP_DESTROY_V2 with subvolids Date: Tue, 13 Jul 2021 13:13:38 +0200 Message-Id: <20210713111344.1149376-19-brauner@kernel.org> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20210713111344.1149376-1-brauner@kernel.org> References: <20210713111344.1149376-1-brauner@kernel.org> MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=2791; h=from:subject; bh=Xm+yqr5sDrgKlUCWrejT8RAVn07B35vb1JCtXAGZZ7k=; b=owGbwMvMwCU28Zj0gdSKO4sYT6slMSS8LY1ROLRp1pkPAVPuTWUOyhUv4ptgL/aZv8z/o/IkvvBX d/8d7yhlYRDjYpAVU2RxaDcJl1vOU7HZKFMDZg4rE8gQBi5OAZgI/2pGhuv77DR23TVdlXZ8ckdO6c 5533+acd54H/7fjmunrnTxhrsM/11ceTUceblXFj6tvbF7685TerkSLC9WbFq/QTLz5RzNJn4A X-Developer-Key: i=christian.brauner@ubuntu.com; a=openpgp; fpr=4880B8C9BD0E5106FC070F4F7B3C391EFEA93624 Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org From: Christian Brauner So far we prevented the deletion of subvolumes and snapshots using subvolume ids possible with the BTRFS_SUBVOL_SPEC_BY_ID flag. This restriction is necessary on idmapped mounts as this allows filesystem wide subvolume and snapshot deletions and thus can escape the scope of what's exposed under the mount identified by the fd passed with the ioctl. Deletion by subvolume id works by looking for an alias of the parent of the subvolume or snapshot to be deleted. The parent alias can be anywhere in the filesystem. However, as long as the alias of the parent that is found is the same as the one identified by the file descriptor passed through the ioctl we can allow the deletion. Cc: Chris Mason Cc: Josef Bacik Cc: Christoph Hellwig Cc: David Sterba Cc: linux-btrfs@vger.kernel.org Signed-off-by: Christian Brauner --- fs/btrfs/ioctl.c | 27 ++++++++++++++++----------- 1 file changed, 16 insertions(+), 11 deletions(-) diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c index dd0fabdbeeeb..586ec4af9777 100644 --- a/fs/btrfs/ioctl.c +++ b/fs/btrfs/ioctl.c @@ -2943,17 +2943,7 @@ static noinline int btrfs_ioctl_snap_destroy(struct file *file, if (err) goto out; } else { - /* - * Deleting by subvolume id can be used to delete - * subvolumes/snapshots anywhere in the filesystem. - * Ensure that users can't abuse idmapped mounts of - * btrfs subvolumes/snapshots to perform operations in - * the whole filesystem. - */ - if (mnt_userns != &init_user_ns) { - err = -EINVAL; - goto out; - } + struct inode *old_dir; if (vol_args2->subvolid < BTRFS_FIRST_FREE_OBJECTID) { err = -EINVAL; @@ -2991,6 +2981,7 @@ static noinline int btrfs_ioctl_snap_destroy(struct file *file, err = PTR_ERR(parent); goto out_drop_write; } + old_dir = dir; dir = d_inode(parent); /* @@ -3001,6 +2992,20 @@ static noinline int btrfs_ioctl_snap_destroy(struct file *file, */ destroy_parent = true; + /* + * On idmapped mounts, deletion via subvolid is + * restricted to subvolumes that are immediate + * ancestors of the inode referenced by the file + * descriptor in the ioctl. Otherwise the idmapping + * could potentially be abused to delete subvolumes + * anywhere in the filesystem the user wouldn't be able + * to delete without an idmapped mount. + */ + if (old_dir != dir && mnt_userns != &init_user_ns) { + err = -EINVAL; + goto free_parent; + } + subvol_name_ptr = btrfs_get_subvol_name_from_objectid( fs_info, vol_args2->subvolid); if (IS_ERR(subvol_name_ptr)) {