From patchwork Fri Feb 14 18:35:36 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Christian Brauner X-Patchwork-Id: 11383039 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 EA41818B8 for ; Fri, 14 Feb 2020 18:38:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D53C62465D for ; Fri, 14 Feb 2020 18:38:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2389498AbgBNSiI (ORCPT ); Fri, 14 Feb 2020 13:38:08 -0500 Received: from youngberry.canonical.com ([91.189.89.112]:33699 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730686AbgBNSiE (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 1j2fqR-0000uO-Mb; Fri, 14 Feb 2020 18:37:43 +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 10/28] sys:__sys_setgid(): handle fsid mappings Date: Fri, 14 Feb 2020 19:35:36 +0100 Message-Id: <20200214183554.1133805-11-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 setgid() 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. 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 | 19 +++++++++++++------ 1 file changed, 13 insertions(+), 6 deletions(-) diff --git a/kernel/sys.c b/kernel/sys.c index a8eefd748327..aa379fb5e93b 100644 --- a/kernel/sys.c +++ b/kernel/sys.c @@ -416,24 +416,31 @@ long __sys_setgid(gid_t gid) const struct cred *old; struct cred *new; int retval; - kgid_t kgid; + kgid_t kgid, kfsgid; kgid = make_kgid(ns, gid); if (!gid_valid(kgid)) return -EINVAL; + kfsgid = make_kfsgid(ns, gid); + if (!gid_valid(kfsgid)) + return -EINVAL; + new = prepare_creds(); if (!new) return -ENOMEM; old = current_cred(); retval = -EPERM; - if (ns_capable(old->user_ns, CAP_SETGID)) - new->gid = new->egid = new->sgid = new->fsgid = kgid; - else if (gid_eq(kgid, old->gid) || gid_eq(kgid, old->sgid)) - new->egid = new->fsgid = kgid; - else + if (ns_capable(old->user_ns, CAP_SETGID)) { + new->gid = new->egid = new->sgid = new->kfsgid = kgid; + new->fsgid = kfsgid; + } else if (gid_eq(kgid, old->gid) || gid_eq(kgid, old->sgid)) { + new->egid = new->kfsgid = kgid; + new->fsgid = kfsgid; + } else { goto error; + } return commit_creds(new);