From patchwork Tue Feb 18 14:34:03 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Christian Brauner X-Patchwork-Id: 11388659 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 E766492A for ; Tue, 18 Feb 2020 14:36:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D31C924670 for ; Tue, 18 Feb 2020 14:36:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727380AbgBROfz (ORCPT ); Tue, 18 Feb 2020 09:35:55 -0500 Received: from youngberry.canonical.com ([91.189.89.112]:53068 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727108AbgBROfm (ORCPT ); Tue, 18 Feb 2020 09:35:42 -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 1j43y5-0000fF-CD; Tue, 18 Feb 2020 14:35:21 +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 v3 17/25] commoncap: cap_bprm_set_creds(): handle fsid mappings Date: Tue, 18 Feb 2020 15:34:03 +0100 Message-Id: <20200218143411.2389182-18-christian.brauner@ubuntu.com> X-Mailer: git-send-email 2.25.0 In-Reply-To: <20200218143411.2389182-1-christian.brauner@ubuntu.com> References: <20200218143411.2389182-1-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 During exec the kfsids are currently reset to the effective kids. To retain the same semantics with the introduction of fsid mappings, we lookup the userspace effective id in the id mappings and translate the effective id into the corresponding kfsid in the fsid mapping. This means, the behavior is unchanged when no fsid mappings are setup and the semantics stay the same even when fsid mappings are setup. Cc: Jann Horn Signed-off-by: Christian Brauner --- /* v2 */ - Christian Brauner : - Reset kfsids used for userns visible filesystems such as proc too. /* v3 */ unchanged --- security/commoncap.c | 17 ++++++++++++++--- 1 file changed, 14 insertions(+), 3 deletions(-) diff --git a/security/commoncap.c b/security/commoncap.c index f4ee0ae106b2..55e6cc24f887 100644 --- a/security/commoncap.c +++ b/security/commoncap.c @@ -24,6 +24,7 @@ #include #include #include +#include /* * If a non-root user executes a setuid-root binary in @@ -810,7 +811,10 @@ int cap_bprm_set_creds(struct linux_binprm *bprm) struct cred *new = bprm->cred; bool effective = false, has_fcap = false, is_setid; int ret; - kuid_t root_uid; + kuid_t root_uid, kfsuid; + kgid_t kfsgid; + uid_t fsuid; + gid_t fsgid; if (WARN_ON(!cap_ambient_invariant_ok(old))) return -EPERM; @@ -847,8 +851,15 @@ int cap_bprm_set_creds(struct linux_binprm *bprm) old->cap_permitted); } - new->suid = new->fsuid = new->euid; - new->sgid = new->fsgid = new->egid; + fsuid = from_kuid_munged(new->user_ns, new->euid); + kfsuid = make_kfsuid(new->user_ns, fsuid); + new->suid = new->kfsuid = new->euid; + new->fsuid = kfsuid; + + fsgid = from_kgid_munged(new->user_ns, new->egid); + kfsgid = make_kfsgid(new->user_ns, fsgid); + new->sgid = new->kfsgid = new->egid; + new->fsgid = kfsgid; /* File caps or setid cancels ambient. */ if (has_fcap || is_setid)