From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id D74F4C433F5 for ; Wed, 9 Feb 2022 19:15:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232688AbiBITPH (ORCPT ); Wed, 9 Feb 2022 14:15:07 -0500 Received: from gmail-smtp-in.l.google.com ([23.128.96.19]:40100 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232298AbiBITPD (ORCPT ); Wed, 9 Feb 2022 14:15:03 -0500 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id EA6BAC0086EA; Wed, 9 Feb 2022 11:14:55 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id C144C61921; Wed, 9 Feb 2022 19:14:49 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9EB5AC340E7; Wed, 9 Feb 2022 19:14:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1644434089; bh=t5k1chf6+v5HfwvAbZWz1wYKfDCyFxon6T1Ca+KqJUM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=aFbai6LqRQ8srZp+gK3iEPk57GtPiSiLANXxwCm2tdcPdvr+SulJblCi3rSQeN7ZQ RRkxRRLes7GIMVity6H1DSioOnCQkmJHMU+zlGeM4YY0xRCmovcIZ4ZpgdIfjbSlTO Mv8TENmDS8gkpKBW5CJG4D/UiTVsVVycfzNRkhTM= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Tabitha Sable , "Eric W. Biederman" , Tejun Heo , =?UTF-8?q?Michal=20Koutn=C3=BD?= Subject: [PATCH 4.9 1/2] cgroup-v1: Require capabilities to set release_agent Date: Wed, 9 Feb 2022 20:13:32 +0100 Message-Id: <20220209191247.878529283@linuxfoundation.org> X-Mailer: git-send-email 2.35.1 In-Reply-To: <20220209191247.830371456@linuxfoundation.org> References: <20220209191247.830371456@linuxfoundation.org> User-Agent: quilt/0.66 X-stable: review X-Patchwork-Hint: ignore MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Eric W. Biederman commit 24f6008564183aa120d07c03d9289519c2fe02af upstream. The cgroup release_agent is called with call_usermodehelper. The function call_usermodehelper starts the release_agent with a full set fo capabilities. Therefore require capabilities when setting the release_agaent. Reported-by: Tabitha Sable Tested-by: Tabitha Sable Fixes: 81a6a5cdd2c5 ("Task Control Groups: automatic userspace notification of idle cgroups") Cc: stable@vger.kernel.org # v2.6.24+ Signed-off-by: "Eric W. Biederman" Signed-off-by: Tejun Heo [mkoutny: Adjust for pre-fs_context, duplicate mount/remount check, drop log messages.] Acked-by: Michal Koutný Signed-off-by: Greg Kroah-Hartman --- kernel/cgroup.c | 26 ++++++++++++++++++++++++++ 1 file changed, 26 insertions(+) --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -1854,6 +1854,7 @@ static int cgroup_remount(struct kernfs_ { int ret = 0; struct cgroup_root *root = cgroup_root_from_kf(kf_root); + struct cgroup_namespace *ns = current->nsproxy->cgroup_ns; struct cgroup_sb_opts opts; u16 added_mask, removed_mask; @@ -1873,6 +1874,13 @@ static int cgroup_remount(struct kernfs_ pr_warn("option changes via remount are deprecated (pid=%d comm=%s)\n", task_tgid_nr(current), current->comm); + /* See cgroup_mount release_agent handling */ + if (opts.release_agent && + ((ns->user_ns != &init_user_ns) || !capable(CAP_SYS_ADMIN))) { + ret = -EINVAL; + goto out_unlock; + } + added_mask = opts.subsys_mask & ~root->subsys_mask; removed_mask = root->subsys_mask & ~opts.subsys_mask; @@ -2248,6 +2256,16 @@ static struct dentry *cgroup_mount(struc goto out_unlock; } + /* + * Release agent gets called with all capabilities, + * require capabilities to set release agent. + */ + if (opts.release_agent && + ((ns->user_ns != &init_user_ns) || !capable(CAP_SYS_ADMIN))) { + ret = -EINVAL; + goto out_unlock; + } + root = kzalloc(sizeof(*root), GFP_KERNEL); if (!root) { ret = -ENOMEM; @@ -3026,6 +3044,14 @@ static ssize_t cgroup_release_agent_writ BUILD_BUG_ON(sizeof(cgrp->root->release_agent_path) < PATH_MAX); + /* + * Release agent gets called with all capabilities, + * require capabilities to set release agent. + */ + if ((of->file->f_cred->user_ns != &init_user_ns) || + !capable(CAP_SYS_ADMIN)) + return -EPERM; + cgrp = cgroup_kn_lock_live(of->kn, false); if (!cgrp) return -ENODEV;