From patchwork Mon Feb 13 15:32:20 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Andreas Gruenbacher X-Patchwork-Id: 727398 Return-Path: X-Original-To: patchwork-incoming@ozlabs.org Delivered-To: patchwork-incoming@ozlabs.org Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id 3vMVHW3WGQz9s7R for ; Tue, 14 Feb 2017 02:45:11 +1100 (AEDT) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753569AbdBMPo5 (ORCPT ); Mon, 13 Feb 2017 10:44:57 -0500 Received: from mx1.redhat.com ([209.132.183.28]:47142 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753317AbdBMPdE (ORCPT ); Mon, 13 Feb 2017 10:33:04 -0500 Received: from int-mx11.intmail.prod.int.phx2.redhat.com (int-mx11.intmail.prod.int.phx2.redhat.com [10.5.11.24]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 6489DAA476; Mon, 13 Feb 2017 15:33:00 +0000 (UTC) Received: from nux.redhat.com (ovpn-117-141.ams2.redhat.com [10.36.117.141]) by int-mx11.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id v1DFWd4O006129; Mon, 13 Feb 2017 10:32:56 -0500 From: Andreas Gruenbacher To: Alexander Viro Cc: Andreas Gruenbacher , Christoph Hellwig , "Theodore Ts'o" , Andreas Dilger , "J. Bruce Fields" , Jeff Layton , Trond Myklebust , Anna Schumaker , Dave Chinner , linux-ext4@vger.kernel.org, linux-xfs@vger.kernel.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-nfs@vger.kernel.org, linux-cifs@vger.kernel.org, linux-api@vger.kernel.org Subject: [PATCH v28 04/21] vfs: Add permission flags for setting file attributes Date: Mon, 13 Feb 2017 16:32:20 +0100 Message-Id: <1486999957-2381-5-git-send-email-agruenba@redhat.com> In-Reply-To: <1486999957-2381-1-git-send-email-agruenba@redhat.com> References: <1486999957-2381-1-git-send-email-agruenba@redhat.com> X-Scanned-By: MIMEDefang 2.68 on 10.5.11.24 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.30]); Mon, 13 Feb 2017 15:33:00 +0000 (UTC) Sender: linux-ext4-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-ext4@vger.kernel.org Richacls support permissions that allow to take ownership of a file, change the file permissions, and set the file timestamps. Support that by introducing new permission mask flags and by checking for those mask flags in setattr_prepare(). Signed-off-by: Andreas Gruenbacher Reviewed-by: J. Bruce Fields Reviewed-by: Steve French Reviewed-by: Jeff Layton --- fs/attr.c | 79 +++++++++++++++++++++++++++++++++++++++++++++--------- include/linux/fs.h | 3 +++ 2 files changed, 70 insertions(+), 12 deletions(-) diff --git a/fs/attr.c b/fs/attr.c index c902b3d..8fa9869 100644 --- a/fs/attr.c +++ b/fs/attr.c @@ -17,6 +17,65 @@ #include /** + * inode_extended_permission - permissions beyond read/write/execute + * + * Check for permissions that only richacls can currently grant. + */ +static int inode_extended_permission(struct inode *inode, int mask) +{ + if (!IS_RICHACL(inode)) + return -EPERM; + return inode_permission(inode, mask); +} + +static bool inode_uid_change_ok(struct inode *inode, kuid_t ia_uid) +{ + if (uid_eq(current_fsuid(), inode->i_uid) && + uid_eq(ia_uid, inode->i_uid)) + return true; + if (uid_eq(current_fsuid(), ia_uid) && + inode_extended_permission(inode, MAY_TAKE_OWNERSHIP) == 0) + return true; + if (capable_wrt_inode_uidgid(inode, CAP_CHOWN)) + return true; + return false; +} + +static bool inode_gid_change_ok(struct inode *inode, kgid_t ia_gid) +{ + int in_group = in_group_p(ia_gid); + if (uid_eq(current_fsuid(), inode->i_uid) && + (in_group || gid_eq(ia_gid, inode->i_gid))) + return true; + if (in_group && inode_extended_permission(inode, MAY_TAKE_OWNERSHIP) == 0) + return true; + if (capable_wrt_inode_uidgid(inode, CAP_CHOWN)) + return true; + return false; +} + +/** + * inode_owner_permitted_or_capable + * + * Check for permissions implicitly granted to the owner, like MAY_CHMOD or + * MAY_SET_TIMES. Equivalent to inode_owner_or_capable for file systems + * without support for those permissions. + */ +static bool inode_owner_permitted_or_capable(struct inode *inode, int mask) +{ + struct user_namespace *ns; + + if (uid_eq(current_fsuid(), inode->i_uid)) + return true; + if (inode_extended_permission(inode, mask) == 0) + return true; + ns = current_user_ns(); + if (ns_capable(ns, CAP_FOWNER) && kuid_has_mapping(ns, inode->i_uid)) + return true; + return false; +} + +/** * setattr_prepare - check if attribute changes to a dentry are allowed * @dentry: dentry to check * @attr: attributes to change @@ -50,22 +109,18 @@ int setattr_prepare(struct dentry *dentry, struct iattr *attr) goto kill_priv; /* Make sure a caller can chown. */ - if ((ia_valid & ATTR_UID) && - (!uid_eq(current_fsuid(), inode->i_uid) || - !uid_eq(attr->ia_uid, inode->i_uid)) && - !capable_wrt_inode_uidgid(inode, CAP_CHOWN)) - return -EPERM; + if (ia_valid & ATTR_UID) + if (!inode_uid_change_ok(inode, attr->ia_uid)) + return -EPERM; /* Make sure caller can chgrp. */ - if ((ia_valid & ATTR_GID) && - (!uid_eq(current_fsuid(), inode->i_uid) || - (!in_group_p(attr->ia_gid) && !gid_eq(attr->ia_gid, inode->i_gid))) && - !capable_wrt_inode_uidgid(inode, CAP_CHOWN)) - return -EPERM; + if (ia_valid & ATTR_GID) + if (!inode_gid_change_ok(inode, attr->ia_gid)) + return -EPERM; /* Make sure a caller can chmod. */ if (ia_valid & ATTR_MODE) { - if (!inode_owner_or_capable(inode)) + if (!inode_owner_permitted_or_capable(inode, MAY_CHMOD)) return -EPERM; /* Also check the setgid bit! */ if (!in_group_p((ia_valid & ATTR_GID) ? attr->ia_gid : @@ -76,7 +131,7 @@ int setattr_prepare(struct dentry *dentry, struct iattr *attr) /* Check for setting the inode time. */ if (ia_valid & (ATTR_MTIME_SET | ATTR_ATIME_SET | ATTR_TIMES_SET)) { - if (!inode_owner_or_capable(inode)) + if (!inode_owner_permitted_or_capable(inode, MAY_SET_TIMES)) return -EPERM; } diff --git a/include/linux/fs.h b/include/linux/fs.h index b495b6c..3de40d3 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -88,6 +88,9 @@ typedef int (dio_iodone_t)(struct kiocb *iocb, loff_t offset, #define MAY_CREATE_DIR 0x00000200 #define MAY_DELETE_CHILD 0x00000400 #define MAY_DELETE_SELF 0x00000800 +#define MAY_TAKE_OWNERSHIP 0x00001000 +#define MAY_CHMOD 0x00002000 +#define MAY_SET_TIMES 0x00004000 /* * flags in file.f_mode. Note that FMODE_READ and FMODE_WRITE must correspond