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 D7805C433EF for ; Wed, 9 Feb 2022 19:15:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231484AbiBITPx (ORCPT ); Wed, 9 Feb 2022 14:15:53 -0500 Received: from gmail-smtp-in.l.google.com ([23.128.96.19]:43392 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233785AbiBITPw (ORCPT ); Wed, 9 Feb 2022 14:15:52 -0500 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 398CAC0045BE; Wed, 9 Feb 2022 11:15:46 -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 ams.source.kernel.org (Postfix) with ESMTPS id 1192FB82390; Wed, 9 Feb 2022 19:15:08 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 42808C340E7; Wed, 9 Feb 2022 19:15:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1644434106; bh=w5dkYAz3sy98SI4aS3c2yCQau3NSXZfCNaqkaqy/TBc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=muBZmCl1ssg9g0xoUpyW8v/HtQty3JmFvYPCIQYecg1GIm0B4nfFN3s1cRctwe6eU 5/ZAmDtnd/4A9uX3wvFDeTrEm16Sjxfb4EE2/U0vWPaFVvjAOg/saCkPud55Av79EB VTa4YEgTaPYBUNX5jxFlhYc9hosfw/btAvR2teXs= 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 4.14 1/3] cgroup-v1: Require capabilities to set release_agent Date: Wed, 9 Feb 2022 20:13:38 +0100 Message-Id: <20220209191248.708176141@linuxfoundation.org> X-Mailer: git-send-email 2.35.1 In-Reply-To: <20220209191248.659458918@linuxfoundation.org> References: <20220209191248.659458918@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: stable@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/cgroup-v1.c | 24 ++++++++++++++++++++++++ 1 file changed, 24 insertions(+) --- a/kernel/cgroup/cgroup-v1.c +++ b/kernel/cgroup/cgroup-v1.c @@ -577,6 +577,14 @@ 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; @@ -1060,6 +1068,7 @@ static int cgroup1_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; @@ -1073,6 +1082,12 @@ static int cgroup1_remount(struct kernfs if (opts.subsys_mask != root->subsys_mask || opts.release_agent) pr_warn("option changes via remount are deprecated (pid=%d comm=%s)\n", task_tgid_nr(current), current->comm); + /* See cgroup1_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; @@ -1236,6 +1251,15 @@ struct dentry *cgroup1_mount(struct file ret = -EPERM; 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) {