From mboxrd@z Thu Jan 1 00:00:00 1970 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=-18.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, 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 00E2DC4361B for ; Mon, 1 Mar 2021 16:54:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id CFAF2650AD for ; Mon, 1 Mar 2021 16:54:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236161AbhCAQxx (ORCPT ); Mon, 1 Mar 2021 11:53:53 -0500 Received: from mail.kernel.org ([198.145.29.99]:50410 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235192AbhCAQrL (ORCPT ); Mon, 1 Mar 2021 11:47:11 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id 6E82D64ED6; Mon, 1 Mar 2021 16:31:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1614616281; bh=i03yslvK3jArK+IX7416ZyRXL0XW3AFRWxLW67Ztv/Q=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=CFNaB1QHAXzKuUA7vhjsiJEeSgBugP+EkQ8BuTaQxXXf4JfMxqOE21cF6QxMwj/mm fsc+o2/nppTyFmWFiNV+zBq6vQ6ZDa3xx36cAFF6lYWx/tEAbewMxboHtzcblNaF1z nmYFTIYFPAUNDX6i/GQbOb+p6bJpJqkTbvvlxuYI= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, "Andrew G. Morgan" , Serge Hallyn , "Eric W. Biederman" , Sasha Levin Subject: [PATCH 4.14 067/176] capabilities: Dont allow writing ambiguous v3 file capabilities Date: Mon, 1 Mar 2021 17:12:20 +0100 Message-Id: <20210301161024.287690890@linuxfoundation.org> X-Mailer: git-send-email 2.30.1 In-Reply-To: <20210301161020.931630716@linuxfoundation.org> References: <20210301161020.931630716@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Eric W. Biederman [ Upstream commit 95ebabde382c371572297915b104e55403674e73 ] The v3 file capabilities have a uid field that records the filesystem uid of the root user of the user namespace the file capabilities are valid in. When someone is silly enough to have the same underlying uid as the root uid of multiple nested containers a v3 filesystem capability can be ambiguous. In the spirit of don't do that then, forbid writing a v3 filesystem capability if it is ambiguous. Fixes: 8db6c34f1dbc ("Introduce v3 namespaced file capabilities") Reviewed-by: Andrew G. Morgan Reviewed-by: Serge Hallyn Signed-off-by: Eric W. Biederman Signed-off-by: Sasha Levin --- security/commoncap.c | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-) diff --git a/security/commoncap.c b/security/commoncap.c index bf689d61b293c..b534c4eee5bea 100644 --- a/security/commoncap.c +++ b/security/commoncap.c @@ -507,7 +507,8 @@ int cap_convert_nscap(struct dentry *dentry, void **ivalue, size_t size) __u32 magic, nsmagic; struct inode *inode = d_backing_inode(dentry); struct user_namespace *task_ns = current_user_ns(), - *fs_ns = inode->i_sb->s_user_ns; + *fs_ns = inode->i_sb->s_user_ns, + *ancestor; kuid_t rootid; size_t newsize; @@ -530,6 +531,15 @@ int cap_convert_nscap(struct dentry *dentry, void **ivalue, size_t size) if (nsrootid == -1) return -EINVAL; + /* + * Do not allow allow adding a v3 filesystem capability xattr + * if the rootid field is ambiguous. + */ + for (ancestor = task_ns->parent; ancestor; ancestor = ancestor->parent) { + if (from_kuid(ancestor, rootid) == 0) + return -EINVAL; + } + newsize = sizeof(struct vfs_ns_cap_data); nscap = kmalloc(newsize, GFP_ATOMIC); if (!nscap) -- 2.27.0