From patchwork Fri Jul 8 16:19:38 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Vivek Goyal X-Patchwork-Id: 9221367 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 6397160467 for ; Fri, 8 Jul 2016 16:21:55 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 541F724B44 for ; Fri, 8 Jul 2016 16:21:55 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 4875924DA2; Fri, 8 Jul 2016 16:21:55 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.9 required=2.0 tests=BAYES_00,RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id C62F224B44 for ; Fri, 8 Jul 2016 16:21:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755954AbcGHQVw (ORCPT ); Fri, 8 Jul 2016 12:21:52 -0400 Received: from mx1.redhat.com ([209.132.183.28]:42784 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755928AbcGHQUD (ORCPT ); Fri, 8 Jul 2016 12:20:03 -0400 Received: from int-mx14.intmail.prod.int.phx2.redhat.com (int-mx14.intmail.prod.int.phx2.redhat.com [10.5.11.27]) (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 C29CB7F088; Fri, 8 Jul 2016 16:20:02 +0000 (UTC) Received: from horse.redhat.com (dhcp-25-69.bos.redhat.com [10.18.25.69]) by int-mx14.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id u68GK1ai012276; Fri, 8 Jul 2016 12:20:01 -0400 Received: by horse.redhat.com (Postfix, from userid 10451) id 7D37D205B9F; Fri, 8 Jul 2016 12:20:01 -0400 (EDT) From: Vivek Goyal To: miklos@szeredi.hu, sds@tycho.nsa.gov, pmoore@redhat.com, casey@schaufler-ca.com, linux-kernel@vger.kernel.org, linux-unionfs@vger.kernel.org, linux-security-module@vger.kernel.org Cc: dwalsh@redhat.com, dhowells@redhat.com, viro@ZenIV.linux.org.uk, vgoyal@redhat.com, linux-fsdevel@vger.kernel.org Subject: [PATCH 3/7] security, overlayfs: Provide security hook for copy up of xattrs for overlay file Date: Fri, 8 Jul 2016 12:19:38 -0400 Message-Id: <1467994782-26474-4-git-send-email-vgoyal@redhat.com> In-Reply-To: <1467994782-26474-1-git-send-email-vgoyal@redhat.com> References: <1467994782-26474-1-git-send-email-vgoyal@redhat.com> X-Scanned-By: MIMEDefang 2.68 on 10.5.11.27 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.26]); Fri, 08 Jul 2016 16:20:02 +0000 (UTC) Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP Provide a security hook which is called when xattrs of a file are being copied up. This hook is called once for each xattr and LSM can return 0 to access the xattr, 1 to reject xattr, -EOPNOTSUPP if none of the lsms claim to know xattr and a negative error code if something went terribly wrong. If 0 or -EOPNOTSUPP is returned, xattr will be copied up, if 1 is returned, xattr will not be copied up and if negative error code is returned, copy up will be aborted. Signed-off-by: David Howells Signed-off-by: Vivek Goyal --- fs/overlayfs/copy_up.c | 7 +++++++ include/linux/lsm_hooks.h | 10 ++++++++++ include/linux/security.h | 6 ++++++ security/security.c | 8 ++++++++ 4 files changed, 31 insertions(+) diff --git a/fs/overlayfs/copy_up.c b/fs/overlayfs/copy_up.c index 8ebea18..68cefb2 100644 --- a/fs/overlayfs/copy_up.c +++ b/fs/overlayfs/copy_up.c @@ -103,6 +103,13 @@ retry: goto retry; } + error = security_inode_copy_up_xattr(name); + if (error < 0 && error != -EOPNOTSUPP) + break; + if (error == 1) { + error = 0; + continue; /* Discard */ + } error = vfs_setxattr(new, name, value, size, 0); if (error) break; diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h index c1f95be..84caead 100644 --- a/include/linux/lsm_hooks.h +++ b/include/linux/lsm_hooks.h @@ -410,6 +410,14 @@ * @src indicates the union dentry of file that is being copied up. * @new pointer to pointer to return newly allocated creds. * Returns 0 on success or a negative error code on error. + * @inode_copy_up_xattr: + * Filter the xattrs being copied up when a unioned file is copied + * up from a lower layer to the union/overlay layer. + * @name indicates the name of the xattr. + * Returns 0 to accept the xattr, 1 to discard the xattr, -EOPNOTSUPP if + * security module does not know about attribute or a negative error code + * to abort the copy up. Note that the caller is responsible for reading + * and writing the xattrs as this hook is merely a filter. * * Security hooks for file operations * @@ -1435,6 +1443,7 @@ union security_list_options { size_t buffer_size); void (*inode_getsecid)(struct inode *inode, u32 *secid); int (*inode_copy_up) (struct dentry *src, struct cred **new); + int (*inode_copy_up_xattr) (const char *name); int (*file_permission)(struct file *file, int mask); int (*file_alloc_security)(struct file *file); @@ -1707,6 +1716,7 @@ struct security_hook_heads { struct list_head inode_listsecurity; struct list_head inode_getsecid; struct list_head inode_copy_up; + struct list_head inode_copy_up_xattr; struct list_head file_permission; struct list_head file_alloc_security; struct list_head file_free_security; diff --git a/include/linux/security.h b/include/linux/security.h index c976d79..08d3191 100644 --- a/include/linux/security.h +++ b/include/linux/security.h @@ -283,6 +283,7 @@ int security_inode_setsecurity(struct inode *inode, const char *name, const void int security_inode_listsecurity(struct inode *inode, char *buffer, size_t buffer_size); void security_inode_getsecid(struct inode *inode, u32 *secid); int security_inode_copy_up(struct dentry *src, struct cred **new); +int security_inode_copy_up_xattr(const char *name); int security_file_permission(struct file *file, int mask); int security_file_alloc(struct file *file); void security_file_free(struct file *file); @@ -764,6 +765,11 @@ static inline int security_inode_copy_up(struct dentry *src, struct cred **new) return 0; } +static inline int security_inode_copy_up_xattr(const char *name) +{ + -EOPNOTSUPP; +} + static inline int security_file_permission(struct file *file, int mask) { return 0; diff --git a/security/security.c b/security/security.c index 3d142aa..3321e31 100644 --- a/security/security.c +++ b/security/security.c @@ -733,6 +733,12 @@ int security_inode_copy_up(struct dentry *src, struct cred **new) } EXPORT_SYMBOL(security_inode_copy_up); +int security_inode_copy_up_xattr(const char *name) +{ + return call_int_hook(inode_copy_up_xattr, -EOPNOTSUPP, name); +} +EXPORT_SYMBOL(security_inode_copy_up_xattr); + int security_file_permission(struct file *file, int mask) { int ret; @@ -1671,6 +1677,8 @@ struct security_hook_heads security_hook_heads = { LIST_HEAD_INIT(security_hook_heads.inode_getsecid), .inode_copy_up = LIST_HEAD_INIT(security_hook_heads.inode_copy_up), + .inode_copy_up_xattr = + LIST_HEAD_INIT(security_hook_heads.inode_copy_up_xattr), .file_permission = LIST_HEAD_INIT(security_hook_heads.file_permission), .file_alloc_security =