From patchwork Thu Jan 21 13:19:35 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Christian Brauner X-Patchwork-Id: 12036725 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=unavailable 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 87DE3C433E6 for ; Thu, 21 Jan 2021 15:32:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5206123A1C for ; Thu, 21 Jan 2021 15:32:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732970AbhAUPan (ORCPT ); Thu, 21 Jan 2021 10:30:43 -0500 Received: from youngberry.canonical.com ([91.189.89.112]:54090 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731136AbhAUNWN (ORCPT ); Thu, 21 Jan 2021 08:22:13 -0500 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 1l2Ztt-0005g7-Cs; Thu, 21 Jan 2021 13:21:25 +0000 From: Christian Brauner To: Alexander Viro , Christoph Hellwig , linux-fsdevel@vger.kernel.org Cc: John Johansen , James Morris , Mimi Zohar , Dmitry Kasatkin , Stephen Smalley , Casey Schaufler , Arnd Bergmann , Andreas Dilger , OGAWA Hirofumi , Geoffrey Thomas , Mrunal Patel , Josh Triplett , Andy Lutomirski , Theodore Tso , Alban Crequy , Tycho Andersen , David Howells , James Bottomley , Seth Forshee , =?utf-8?q?St=C3=A9phane_Graber?= , Linus Torvalds , Aleksa Sarai , Lennart Poettering , "Eric W. Biederman" , smbarber@chromium.org, Phil Estes , Serge Hallyn , Kees Cook , Todd Kjos , Paul Moore , Jonathan Corbet , containers@lists.linux-foundation.org, linux-security-module@vger.kernel.org, linux-api@vger.kernel.org, linux-ext4@vger.kernel.org, linux-xfs@vger.kernel.org, linux-integrity@vger.kernel.org, selinux@vger.kernel.org, Christian Brauner Subject: [PATCH v6 16/40] open: handle idmapped mounts Date: Thu, 21 Jan 2021 14:19:35 +0100 Message-Id: <20210121131959.646623-17-christian.brauner@ubuntu.com> X-Mailer: git-send-email 2.30.0 In-Reply-To: <20210121131959.646623-1-christian.brauner@ubuntu.com> References: <20210121131959.646623-1-christian.brauner@ubuntu.com> MIME-Version: 1.0 X-Patch-Hashes: v=1; h=sha256; i=YKSd0FdGGLgCSTeDw7b6sTvRU/kXPfMpmc0z0c+ceJs=; m=QtXKH7l01QTmlgDZWGGLs41QsIHJYr2I07NJQrbQhUc=; p=UQ8ZL9iZHePP4j74jgLUJqMxCUpzv40jcAqgWmdc+iM=; g=fc42bb0317f59f78c12f1f5b6f750e685efc9c8e X-Patch-Sig: m=pgp; i=christian.brauner@ubuntu.com; s=0x0x91C61BC06578DCA2; b=iHQEABYKAB0WIQRAhzRXHqcMeLMyaSiRxhvAZXjcogUCYAl9pAAKCRCRxhvAZXjcom58APiYXnz MLA9PdyDTNWHJ1hzxQwmhv0RHo0AradNsIDslAQDIvEnNGlH+yVfr0r/waOULLGeiGRFi0nzVv0+4 7M8YDg== Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org For core file operations such as changing directories or chrooting, determining file access, changing mode or ownership the vfs will verify that the caller is privileged over the inode. Extend the various helpers to handle idmapped mounts. If the inode is accessed through an idmapped mount map it into the mount's user namespace. Afterwards the permissions checks are identical to non-idmapped mounts. When changing file ownership we need to map the uid and gid from the mount's user namespace. If the initial user namespace is passed nothing changes so non-idmapped mounts will see identical behavior as before. Link: https://lore.kernel.org/r/20210112220124.837960-24-christian.brauner@ubuntu.com Cc: Christoph Hellwig Cc: David Howells Cc: Al Viro Cc: linux-fsdevel@vger.kernel.org Signed-off-by: Christian Brauner Reviewed-by: James Morris Reviewed-by: Christoph Hellwig --- /* v2 */ unchanged /* v3 */ - David Howells : - Remove mnt_idmapped() check after removing mnt_idmapped() helper in earlier patches. /* v4 */ - Serge Hallyn : - Use "mnt_userns" to refer to a vfsmount's userns everywhere to make terminology consistent. /* v5 */ unchanged base-commit: 7c53f6b671f4aba70ff15e1b05148b10d58c2837 - Christoph Hellwig : - Use new file_mnt_user_ns() helper. /* v6 */ base-commit: 19c329f6808995b142b3966301f217c831e7cf31 - Christoph Hellwig : - Make use of new path_permission() helper. --- fs/open.c | 13 +++++++++---- 1 file changed, 9 insertions(+), 4 deletions(-) diff --git a/fs/open.c b/fs/open.c index 8b3f3eb652d0..4ec3979d0466 100644 --- a/fs/open.c +++ b/fs/open.c @@ -438,7 +438,7 @@ static long do_faccessat(int dfd, const char __user *filename, int mode, int fla goto out_path_release; } - res = inode_permission(&init_user_ns, inode, mode | MAY_ACCESS); + res = inode_permission(mnt_user_ns(path.mnt), inode, mode | MAY_ACCESS); /* SuS v2 requires we report a read only fs too */ if (res || !(mode & S_IWOTH) || special_file(inode->i_mode)) goto out_path_release; @@ -582,8 +582,8 @@ int chmod_common(const struct path *path, umode_t mode) goto out_unlock; newattrs.ia_mode = (mode & S_IALLUGO) | (inode->i_mode & ~S_IALLUGO); newattrs.ia_valid = ATTR_MODE | ATTR_CTIME; - error = notify_change(&init_user_ns, path->dentry, &newattrs, - &delegated_inode); + error = notify_change(mnt_user_ns(path->mnt), path->dentry, + &newattrs, &delegated_inode); out_unlock: inode_unlock(inode); if (delegated_inode) { @@ -644,6 +644,7 @@ SYSCALL_DEFINE2(chmod, const char __user *, filename, umode_t, mode) int chown_common(const struct path *path, uid_t user, gid_t group) { + struct user_namespace *mnt_userns; struct inode *inode = path->dentry->d_inode; struct inode *delegated_inode = NULL; int error; @@ -654,6 +655,10 @@ int chown_common(const struct path *path, uid_t user, gid_t group) uid = make_kuid(current_user_ns(), user); gid = make_kgid(current_user_ns(), group); + mnt_userns = mnt_user_ns(path->mnt); + uid = kuid_from_mnt(mnt_userns, uid); + gid = kgid_from_mnt(mnt_userns, gid); + retry_deleg: newattrs.ia_valid = ATTR_CTIME; if (user != (uid_t) -1) { @@ -674,7 +679,7 @@ int chown_common(const struct path *path, uid_t user, gid_t group) inode_lock(inode); error = security_path_chown(path, uid, gid); if (!error) - error = notify_change(&init_user_ns, path->dentry, &newattrs, + error = notify_change(mnt_userns, path->dentry, &newattrs, &delegated_inode); inode_unlock(inode); if (delegated_inode) {