From patchwork Wed Jul 13 15:13:56 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Vivek Goyal X-Patchwork-Id: 9227803 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 8A1EC6088F for ; Wed, 13 Jul 2016 15:17:42 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 7BF0E27F96 for ; Wed, 13 Jul 2016 15:17:42 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 6FA5127F94; Wed, 13 Jul 2016 15:17:42 +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 D6E3E27F96 for ; Wed, 13 Jul 2016 15:17:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753161AbcGMPOH (ORCPT ); Wed, 13 Jul 2016 11:14:07 -0400 Received: from mx1.redhat.com ([209.132.183.28]:40086 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752527AbcGMPOF (ORCPT ); Wed, 13 Jul 2016 11:14:05 -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 17962D6842; Wed, 13 Jul 2016 15:13:57 +0000 (UTC) Received: from horse.redhat.com (dhcp-25-90.bos.redhat.com [10.18.25.90]) by int-mx14.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id u6DFDuvu028230; Wed, 13 Jul 2016 11:13:56 -0400 Received: by horse.redhat.com (Postfix, from userid 10451) id 2E08A205FC8; Wed, 13 Jul 2016 11:13:56 -0400 (EDT) Date: Wed, 13 Jul 2016 11:13:56 -0400 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, linux-fsdevel@vger.kernel.org Subject: Re: [PATCH 1/9] security, overlayfs: provide copy up security hook for unioned files Message-ID: <20160713151356.GF16900@redhat.com> References: <1468421095-22322-1-git-send-email-vgoyal@redhat.com> <1468421095-22322-2-git-send-email-vgoyal@redhat.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <1468421095-22322-2-git-send-email-vgoyal@redhat.com> User-Agent: Mutt/1.6.1 (2016-04-27) 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 [10.5.110.39]); Wed, 13 Jul 2016 15:14:00 +0000 (UTC) Sender: owner-linux-security-module@vger.kernel.org Precedence: bulk List-ID: X-Virus-Scanned: ClamAV using ClamSMTP Updated patch as per Stephen's feedback. Provide a security hook to label new file correctly when a file is copied up from lower layer to upper layer of a overlay/union mount. This hook can prepare a new set of creds which are suitable for new file creation during copy up. Caller will use new creds to create file and then revert back to old creds and release new creds. Signed-off-by: Vivek Goyal Acked-by: Stephen Smalley --- fs/overlayfs/copy_up.c | 15 +++++++++++++++ include/linux/lsm_hooks.h | 11 +++++++++++ include/linux/security.h | 6 ++++++ security/security.c | 8 ++++++++ 4 files changed, 40 insertions(+) diff --git a/fs/overlayfs/copy_up.c b/fs/overlayfs/copy_up.c index 80aa6f1..e5e3557 100644 --- a/fs/overlayfs/copy_up.c +++ b/fs/overlayfs/copy_up.c @@ -246,6 +246,8 @@ static int ovl_copy_up_locked(struct dentry *workdir, struct dentry *upperdir, struct dentry *upper = NULL; umode_t mode = stat->mode; int err; + const struct cred *old_creds = NULL; + struct cred *new_creds = NULL; newdentry = ovl_lookup_temp(workdir, dentry); err = PTR_ERR(newdentry); @@ -258,10 +260,23 @@ static int ovl_copy_up_locked(struct dentry *workdir, struct dentry *upperdir, if (IS_ERR(upper)) goto out1; + err = security_inode_copy_up(dentry, &new_creds); + if (err < 0) + goto out2; + + if (new_creds) + old_creds = override_creds(new_creds); + /* Can't properly set mode on creation because of the umask */ stat->mode &= S_IFMT; err = ovl_create_real(wdir, newdentry, stat, link, NULL, true); stat->mode = mode; + + if (new_creds) { + revert_creds(old_creds); + put_cred(new_creds); + } + if (err) goto out2; diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h index 7ae3976..c1f95be 100644 --- a/include/linux/lsm_hooks.h +++ b/include/linux/lsm_hooks.h @@ -401,6 +401,15 @@ * @inode contains a pointer to the inode. * @secid contains a pointer to the location where result will be saved. * In case of failure, @secid will be set to zero. + * @inode_copy_up: + * A file is about to be copied up from lower layer to upper layer of + * overlay filesystem. Security module can prepare a set of new creds + * and modify as need be and return new creds. Caller will switch to + * new creds temporarily to create new file and release newly allocated + * creds. + * @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. * * Security hooks for file operations * @@ -1425,6 +1434,7 @@ union security_list_options { int (*inode_listsecurity)(struct inode *inode, char *buffer, size_t buffer_size); void (*inode_getsecid)(struct inode *inode, u32 *secid); + int (*inode_copy_up) (struct dentry *src, struct cred **new); int (*file_permission)(struct file *file, int mask); int (*file_alloc_security)(struct file *file); @@ -1696,6 +1706,7 @@ struct security_hook_heads { struct list_head inode_setsecurity; struct list_head inode_listsecurity; struct list_head inode_getsecid; + struct list_head inode_copy_up; 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 14df373..c976d79 100644 --- a/include/linux/security.h +++ b/include/linux/security.h @@ -282,6 +282,7 @@ int security_inode_getsecurity(struct inode *inode, const char *name, void **buf int security_inode_setsecurity(struct inode *inode, const char *name, const void *value, size_t size, int flags); 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_file_permission(struct file *file, int mask); int security_file_alloc(struct file *file); void security_file_free(struct file *file); @@ -758,6 +759,11 @@ static inline void security_inode_getsecid(struct inode *inode, u32 *secid) *secid = 0; } +static inline int security_inode_copy_up(struct dentry *src, struct cred **new) +{ + return 0; +} + static inline int security_file_permission(struct file *file, int mask) { return 0; diff --git a/security/security.c b/security/security.c index 7095693..3d142aa 100644 --- a/security/security.c +++ b/security/security.c @@ -727,6 +727,12 @@ void security_inode_getsecid(struct inode *inode, u32 *secid) call_void_hook(inode_getsecid, inode, secid); } +int security_inode_copy_up(struct dentry *src, struct cred **new) +{ + return call_int_hook(inode_copy_up, 0, src, new); +} +EXPORT_SYMBOL(security_inode_copy_up); + int security_file_permission(struct file *file, int mask) { int ret; @@ -1663,6 +1669,8 @@ struct security_hook_heads security_hook_heads = { LIST_HEAD_INIT(security_hook_heads.inode_listsecurity), .inode_getsecid = LIST_HEAD_INIT(security_hook_heads.inode_getsecid), + .inode_copy_up = + LIST_HEAD_INIT(security_hook_heads.inode_copy_up), .file_permission = LIST_HEAD_INIT(security_hook_heads.file_permission), .file_alloc_security =