From patchwork Fri Feb 14 18:35:37 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Christian Brauner X-Patchwork-Id: 11382999 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 19D891820 for ; Fri, 14 Feb 2020 18:38:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0372A2467C for ; Fri, 14 Feb 2020 18:38:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388787AbgBNSiE (ORCPT ); Fri, 14 Feb 2020 13:38:04 -0500 Received: from youngberry.canonical.com ([91.189.89.112]:33694 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730663AbgBNSiE (ORCPT ); Fri, 14 Feb 2020 13:38:04 -0500 Received: from ip5f5bf7ec.dynamic.kabel-deutschland.de ([95.91.247.236] 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 1j2fqS-0000uO-Te; Fri, 14 Feb 2020 18:37:45 +0000 From: Christian Brauner To: =?utf-8?q?St=C3=A9phane_Graber?= , "Eric W. Biederman" , Aleksa Sarai , Jann Horn Cc: smbarber@chromium.org, Seth Forshee , Alexander Viro , Alexey Dobriyan , Serge Hallyn , James Morris , Kees Cook , Jonathan Corbet , Phil Estes , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, containers@lists.linux-foundation.org, linux-security-module@vger.kernel.org, linux-api@vger.kernel.org, Christian Brauner Subject: [PATCH v2 11/28] sys:__sys_setreuid(): handle fsid mappings Date: Fri, 14 Feb 2020 19:35:37 +0100 Message-Id: <20200214183554.1133805-12-christian.brauner@ubuntu.com> X-Mailer: git-send-email 2.25.0 In-Reply-To: <20200214183554.1133805-1-christian.brauner@ubuntu.com> References: <20200214183554.1133805-1-christian.brauner@ubuntu.com> MIME-Version: 1.0 Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org Switch setreuid() to lookup fsids in the fsid mappings. If no fsid mappings are setup the behavior is unchanged, i.e. fsids are looked up in the id mappings. During setreuid() the kfsuid is set to the keuid corresponding the euid that is requested by userspace. If the requested euid is -1 the kfsuid is reset to the current keuid. For the latter case this means we need to lookup the corresponding userspace euid corresponding to the current keuid in the id mappings and translate this euid into the corresponding kfsuid in the fsid mappings. The kfsid to cleanly handle userns visible filesystem is set as before. We require that a user must have a valid fsid mapping for the target id. This is consistent with how the setid calls work today without fsid mappings. Signed-off-by: Christian Brauner --- /* v2 */ - Christian Brauner : - set kfsid which is used when dealing with proc permission checking --- kernel/sys.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) diff --git a/kernel/sys.c b/kernel/sys.c index aa379fb5e93b..4697e010bbd7 100644 --- a/kernel/sys.c +++ b/kernel/sys.c @@ -504,7 +504,7 @@ long __sys_setreuid(uid_t ruid, uid_t euid) const struct cred *old; struct cred *new; int retval; - kuid_t kruid, keuid; + kuid_t kruid, keuid, kfsuid; kruid = make_kuid(ns, ruid); keuid = make_kuid(ns, euid); @@ -535,6 +535,13 @@ long __sys_setreuid(uid_t ruid, uid_t euid) !uid_eq(old->suid, keuid) && !ns_capable_setid(old->user_ns, CAP_SETUID)) goto error; + kfsuid = make_kfsuid(new->user_ns, euid); + } else { + kfsuid = kuid_to_kfsuid(new->user_ns, new->euid); + } + if (!uid_valid(kfsuid)) { + retval = -EINVAL; + goto error; } if (!uid_eq(new->uid, old->uid)) { @@ -545,7 +552,8 @@ long __sys_setreuid(uid_t ruid, uid_t euid) if (ruid != (uid_t) -1 || (euid != (uid_t) -1 && !uid_eq(keuid, old->uid))) new->suid = new->euid; - new->fsuid = new->euid; + new->kfsuid = new->euid; + new->fsuid = kfsuid; retval = security_task_fix_setuid(new, old, LSM_SETID_RE); if (retval < 0)