From patchwork Fri Feb 14 18:35:34 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Christian Brauner X-Patchwork-Id: 11383047 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 CB3BF1820 for ; Fri, 14 Feb 2020 18:38:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B49F8222C2 for ; Fri, 14 Feb 2020 18:38:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728239AbgBNSiC (ORCPT ); Fri, 14 Feb 2020 13:38:02 -0500 Received: from youngberry.canonical.com ([91.189.89.112]:33667 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730561AbgBNSiC (ORCPT ); Fri, 14 Feb 2020 13:38:02 -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 1j2fqP-0000uO-HU; Fri, 14 Feb 2020 18:37:41 +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 08/28] sys: __sys_setfsgid(): handle fsid mappings Date: Fri, 14 Feb 2020 19:35:34 +0100 Message-Id: <20200214183554.1133805-9-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: owner-linux-security-module@vger.kernel.org Precedence: bulk List-ID: Switch setfsgid() 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. A caller can only setfs{g,u}id() to a given id if the id maps to a valid kid in both the id and fsid maps of the caller's user namespace. This is always the case when no id mappings and fsid mappings have been written. It is also always the case when an id mapping has been written which includes the target id and but no fsid mappings have been written. All non-fsid mapping aware workloads will thus work just as before. Requiring a valid mapping for the target id in both the id and fsid mappings of the container simplifies permission checking for userns visible filesystems such as proc. Signed-off-by: Christian Brauner --- /* v2 */ - Christian Brauner : - Set unmapped fsid as well. --- kernel/sys.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) diff --git a/kernel/sys.c b/kernel/sys.c index 13f790dbda71..864fa78f25a7 100644 --- a/kernel/sys.c +++ b/kernel/sys.c @@ -849,15 +849,19 @@ long __sys_setfsgid(gid_t gid) const struct cred *old; struct cred *new; gid_t old_fsgid; - kgid_t kgid; + kgid_t kgid, kfsgid; old = current_cred(); - old_fsgid = from_kgid_munged(old->user_ns, old->fsgid); + old_fsgid = from_kfsgid_munged(old->user_ns, old->fsgid); - kgid = make_kgid(old->user_ns, gid); + kgid = make_kfsgid(old->user_ns, gid); if (!gid_valid(kgid)) return old_fsgid; + kfsgid = make_kgid(old->user_ns, gid); + if (!gid_valid(kfsgid)) + return old_fsgid; + new = prepare_creds(); if (!new) return old_fsgid; @@ -867,6 +871,7 @@ long __sys_setfsgid(gid_t gid) ns_capable(old->user_ns, CAP_SETGID)) { if (!gid_eq(kgid, old->fsgid)) { new->fsgid = kgid; + new->kfsgid = kfsgid; goto change_okay; } }