From patchwork Mon Feb 14 13:35:12 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Thadeu Lima de Souza Cascardo X-Patchwork-Id: 1592535 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=iWqQ35ME; 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 4Jy4xy2bkWz9s8s for ; Tue, 15 Feb 2022 00:36:38 +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 1nJbWr-00058e-CR; Mon, 14 Feb 2022 13:36:33 +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 1nJbWp-00057q-Qn for kernel-team@lists.ubuntu.com; Mon, 14 Feb 2022 13:36:31 +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 ACEBC3FD39 for ; Mon, 14 Feb 2022 13:36:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=canonical.com; s=20210705; t=1644845791; bh=coG/3tuk/FF54Mxih0zqSXkL79DMfrdCRn+JURcDmUY=; h=From:To:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=iWqQ35MEiDVZeSxY6DLXL87AGl0oNyDt8Ft8XRsNP8slHMPs4C9d5C7cCw9k9Hgys qt49P5yyfY7TRmnFHr/uLjggJVlqzQqp9FTZ2NlFcmVAKOf+muC4Qnh2S2qzVgrvHc P/Si7SK70irTgVJMgRU2+i77uD6rFpg9kBJIZ45p52qSm5Yi10JaitckzWDEyFArVA ioTqVIPE9wEL+wMzVQuqkeoyNFacVc0JrSYWzTgSu7LoBwifcJ5tb2idUmKqolM5Al U7rm83J4JZ3WlxO1uqlbXYPYMdiKvN6fIyNpP7sFhkv78DiMLIaDb6p2EnxYlb9qld tT/GJzbHsMkcg== From: Thadeu Lima de Souza Cascardo To: kernel-team@lists.ubuntu.com Subject: [SRU Focal 1/1] cgroup-v1: Require capabilities to set release_agent Date: Mon, 14 Feb 2022 10:35:12 -0300 Message-Id: <20220214133514.233255-3-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 Signed-off-by: Greg Kroah-Hartman (cherry picked from commit 0e8283cbe4996ae046cd680b3ed598a8f2b0d5d8 linux-5.4.y) CVE-2022-0492 Signed-off-by: Thadeu Lima de Souza Cascardo --- kernel/cgroup/cgroup-v1.c | 14 ++++++++++++++ 1 file changed, 14 insertions(+) diff --git a/kernel/cgroup/cgroup-v1.c b/kernel/cgroup/cgroup-v1.c index 2d0ef613ca07..5e465c4b1e64 100644 --- a/kernel/cgroup/cgroup-v1.c +++ b/kernel/cgroup/cgroup-v1.c @@ -549,6 +549,14 @@ 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; @@ -961,6 +969,12 @@ int cgroup1_parse_param(struct fs_context *fc, struct fs_parameter *param) /* Specifying two release agents is forbidden */ if (ctx->release_agent) return cg_invalf(fc, "cgroup1: release_agent respecified"); + /* + * Release agent gets called with all capabilities, + * require capabilities to set release agent. + */ + if ((fc->user_ns != &init_user_ns) || !capable(CAP_SYS_ADMIN)) + return cg_invalf(fc, "cgroup1: Setting release_agent not allowed"); ctx->release_agent = param->string; param->string = NULL; break;