From patchwork Tue Feb 11 16:57:49 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Christian Brauner X-Patchwork-Id: 11375983 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 7CC5C14E3 for ; Tue, 11 Feb 2020 17:00:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 667A6208C3 for ; Tue, 11 Feb 2020 17:00:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731109AbgBKRAd (ORCPT ); Tue, 11 Feb 2020 12:00:33 -0500 Received: from youngberry.canonical.com ([91.189.89.112]:53528 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728211AbgBKRAa (ORCPT ); Tue, 11 Feb 2020 12:00:30 -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 1j1Ysf-00014T-R7; Tue, 11 Feb 2020 16:59:25 +0000 From: Christian Brauner To: =?utf-8?q?St=C3=A9phane_Graber?= , "Eric W. Biederman" , Aleksa Sarai , Jann Horn Cc: smbarber@chromium.org, Alexander Viro , Alexey Dobriyan , Serge Hallyn , James Morris , Kees Cook , Jonathan Corbet , 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 20/24] sys:__sys_setreuid(): handle fsid mappings Date: Tue, 11 Feb 2020 17:57:49 +0100 Message-Id: <20200211165753.356508-21-christian.brauner@ubuntu.com> X-Mailer: git-send-email 2.25.0 In-Reply-To: <20200211165753.356508-1-christian.brauner@ubuntu.com> References: <20200211165753.356508-1-christian.brauner@ubuntu.com> MIME-Version: 1.0 Sender: owner-linux-security-module@vger.kernel.org Precedence: bulk List-ID: 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. Signed-off-by: Christian Brauner --- kernel/sys.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) diff --git a/kernel/sys.c b/kernel/sys.c index 11f41e0a4974..ef1104c9df56 100644 --- a/kernel/sys.c +++ b/kernel/sys.c @@ -504,15 +504,18 @@ 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); + kfsuid = make_kfsuid(ns, euid); if ((ruid != (uid_t) -1) && !uid_valid(kruid)) return -EINVAL; if ((euid != (uid_t) -1) && !uid_valid(keuid)) return -EINVAL; + if ((euid != (uid_t) -1) && !uid_valid(kfsuid)) + return -EINVAL; new = prepare_creds(); if (!new) @@ -535,6 +538,9 @@ long __sys_setreuid(uid_t ruid, uid_t euid) !uid_eq(old->suid, keuid) && !ns_capable_setid(old->user_ns, CAP_SETUID)) goto error; + } else { + uid_t fsuid = from_kuid_munged(new->user_ns, new->euid); + kfsuid = make_kfsuid(ns, fsuid); } if (!uid_eq(new->uid, old->uid)) { @@ -545,7 +551,7 @@ 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->fsuid = kfsuid; retval = security_task_fix_setuid(new, old, LSM_SETID_RE); if (retval < 0)