From patchwork Tue Mar 16 11:22:57 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Christian Brauner X-Patchwork-Id: 12141969 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=-16.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,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 0699DC433E0 for ; Tue, 16 Mar 2021 11:24:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C9CFB6501D for ; Tue, 16 Mar 2021 11:24:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229862AbhCPLXc (ORCPT ); Tue, 16 Mar 2021 07:23:32 -0400 Received: from youngberry.canonical.com ([91.189.89.112]:43404 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229636AbhCPLXJ (ORCPT ); Tue, 16 Mar 2021 07:23:09 -0400 Received: from ip5f5af0a0.dynamic.kabel-deutschland.de ([95.90.240.160] helo=wittgenstein.fritz.box) by youngberry.canonical.com with esmtpsa (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.86_2) (envelope-from ) id 1lM7n0-0006XY-2K; Tue, 16 Mar 2021 11:23:06 +0000 From: Christian Brauner To: David Howells , linux-cachefs@redhat.com Cc: linux-fsdevel@vger.kernel.org, Christian Brauner Subject: [PATCH] cachefiles: do not yet allow on idmapped mounts Date: Tue, 16 Mar 2021 12:22:57 +0100 Message-Id: <20210316112257.2974212-1-christian.brauner@ubuntu.com> X-Mailer: git-send-email 2.27.0 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org Based on discussion with David Howells my understanding of cachefiles and the cachefiles userspace daemon is that it creates a cache on a local filesystem (e.g. ext4, xfs etc.) for a network filesystem. The way this is done is by writing "bind" to /dev/cachefiles and pointing it to the directory to use as the cache. So from our offline discussion I gather that cachefilesd creates a cache on a local filesystem (ext4, xfs etc.) for a network filesystem. The way this is done is by writing "bind" to /dev/cachefiles and pointing it to a directory to use as the cache. Currently this directory can technically also be an idmapped mount but cachefiles aren't yet fully aware of such mounts and thus don't take the idmapping into account. This could leave users confused as the ownership of the files wouldn't match to what they expressed in the idmapping. So let's not allow this for now and only make cachefiles aware of idmapped mounts after it's current rewrite/rework is done. Link: https://lore.kernel.org/lkml/20210303161528.n3jzg66ou2wa43qb@wittgenstein Cc: David Howells Cc: linux-cachefs@redhat.com Signed-off-by: Christian Brauner --- fs/cachefiles/bind.c | 4 ++++ 1 file changed, 4 insertions(+) base-commit: 1e28eed17697bcf343c6743f0028cc3b5dd88bf0 diff --git a/fs/cachefiles/bind.c b/fs/cachefiles/bind.c index dfb14dbddf51..bd7eab9a0539 100644 --- a/fs/cachefiles/bind.c +++ b/fs/cachefiles/bind.c @@ -115,6 +115,10 @@ static int cachefiles_daemon_add_cache(struct cachefiles_cache *cache) if (ret < 0) goto error_open_root; + ret = -EINVAL; + if (mnt_user_ns(path.mnt) != &init_user_ns) + goto error_unsupported; + cache->mnt = path.mnt; root = path.dentry;