From patchwork Mon Feb 14 13:35:11 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Thadeu Lima de Souza Cascardo X-Patchwork-Id: 1592534 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Authentication-Results: bilbo.ozlabs.org; dkim=fail reason="signature verification failed" (2048-bit key; unprotected) header.d=canonical.com header.i=@canonical.com header.a=rsa-sha256 header.s=20210705 header.b=pEUq2oKn; dkim-atps=neutral Authentication-Results: ozlabs.org; spf=none (no SPF record) smtp.mailfrom=lists.ubuntu.com (client-ip=91.189.94.19; helo=huckleberry.canonical.com; envelope-from=kernel-team-bounces@lists.ubuntu.com; receiver=) Received: from huckleberry.canonical.com (huckleberry.canonical.com [91.189.94.19]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by bilbo.ozlabs.org (Postfix) with ESMTPS id 4Jy4xt5lGDz9s8s for ; Tue, 15 Feb 2022 00:36:34 +1100 (AEDT) Received: from localhost ([127.0.0.1] helo=huckleberry.canonical.com) by huckleberry.canonical.com with esmtp (Exim 4.86_2) (envelope-from ) id 1nJbWn-00056X-5r; Mon, 14 Feb 2022 13:36:29 +0000 Received: from smtp-relay-canonical-1.internal ([10.131.114.174] helo=smtp-relay-canonical-1.canonical.com) by huckleberry.canonical.com with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.86_2) (envelope-from ) id 1nJbWm-00056B-97 for kernel-team@lists.ubuntu.com; Mon, 14 Feb 2022 13:36:28 +0000 Received: from localhost.localdomain (1.general.cascardo.us.vpn [10.172.70.58]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by smtp-relay-canonical-1.canonical.com (Postfix) with ESMTPSA id 384AA3FD39 for ; Mon, 14 Feb 2022 13:36:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=canonical.com; s=20210705; t=1644845788; bh=qDA30n9F9gMk/fSsHloWI0A0//XSOCv6fNJ1rcw2RVM=; h=From:To:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version:Content-Type; b=pEUq2oKnb7vVYcA4uX77ZU7bq9WS6IP+cTXxcp/SuN/hu1ZkVu/oovGevGkrWIOuQ kQdrK9F72cW8bneKc77WSHb40Oq+GCRE0/2nI+h5Y5pA+yJUcP6uTRkkDZF0kU/g3+ AOVoPnY4GLhsItDLT75yjHwSfjIc43fA3D+STkwZQEQfXENYykb61MkA9aDhdcZFRm yEWRcy42jYBkbXzLSzWU2cu4GBrtpcrP9VuEVTIEthdb/wgqBXvnWOQDUSwQ5RbytR DgAIMp8OIDV/ElYKrCAahpx9KVEwr+ikmOS3luExTjNnE846VZXurIxQHVDSuuf16n 9aooamA5iIyvw== From: Thadeu Lima de Souza Cascardo To: kernel-team@lists.ubuntu.com Subject: [SRU Bionic 1/1] cgroup-v1: Require capabilities to set release_agent Date: Mon, 14 Feb 2022 10:35:11 -0300 Message-Id: <20220214133514.233255-2-cascardo@canonical.com> X-Mailer: git-send-email 2.32.0 In-Reply-To: <20220214133514.233255-1-cascardo@canonical.com> References: <20220214133514.233255-1-cascardo@canonical.com> MIME-Version: 1.0 X-BeenThere: kernel-team@lists.ubuntu.com X-Mailman-Version: 2.1.20 Precedence: list List-Id: Kernel team discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: kernel-team-bounces@lists.ubuntu.com Sender: "kernel-team" 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 (cherry picked from commit b391bb3554dd6e04b7a8ede975dbd3342526a045 linux-4.14.y) CVE-2022-0492 Signed-off-by: Thadeu Lima de Souza Cascardo --- kernel/cgroup/cgroup-v1.c | 24 ++++++++++++++++++++++++ 1 file changed, 24 insertions(+) diff --git a/kernel/cgroup/cgroup-v1.c b/kernel/cgroup/cgroup-v1.c index 5602bd81caa9..105f5b2f5978 100644 --- a/kernel/cgroup/cgroup-v1.c +++ b/kernel/cgroup/cgroup-v1.c @@ -577,6 +577,14 @@ static ssize_t cgroup_release_agent_write(struct kernfs_open_file *of, 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_root *kf_root, int *flags, char *data) { 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_root *kf_root, int *flags, char *data) 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_system_type *fs_type, int flags, 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) {