From patchwork Fri Jun 30 18:39:06 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: =?utf-8?q?Michal_Koutn=C3=BD?= X-Patchwork-Id: 698366 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 CA90CEB64DA for ; Fri, 30 Jun 2023 18:39:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232866AbjF3SjT (ORCPT ); Fri, 30 Jun 2023 14:39:19 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45006 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231765AbjF3SjP (ORCPT ); Fri, 30 Jun 2023 14:39:15 -0400 Received: from smtp-out2.suse.de (smtp-out2.suse.de [IPv6:2001:67c:2178:6::1d]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 80E1D19BA; Fri, 30 Jun 2023 11:39:12 -0700 (PDT) Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by smtp-out2.suse.de (Postfix) with ESMTPS id 23E451F8C2; Fri, 30 Jun 2023 18:39:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1688150351; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=bCYIN6pQvd3q6SAnjV/5aG2ZzwJfRdxp+vjhFcp2bPA=; b=ncRyoeohjhmpusu0eYkwkCXqkCCcASKdr/ptw+5pVYntM8z5o07EoURaFYu4TjdrbyOAdL 8gvtcMsDhFDyCCcts6J5q3lyrT7PYVJ1ZWYdaJ2n+/4E8RLftf8KZEA86Au4jA6bRh3Kxy xkgQjZ0Oa56WYkfK3GcEUlS6oW09bgQ= Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap2.suse-dmz.suse.de (Postfix) with ESMTPS id F05CE139FF; Fri, 30 Jun 2023 18:39:10 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id CIvTOU4hn2QgbQAAMHmgww (envelope-from ); Fri, 30 Jun 2023 18:39:10 +0000 From: =?utf-8?q?Michal_Koutn=C3=BD?= To: linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, linux-kselftest@vger.kernel.org Cc: Waiman Long , Zefan Li , Tejun Heo , Johannes Weiner , Shuah Khan Subject: [PATCH v2 1/3] cpuset: Allow setscheduler regardless of manipulated task Date: Fri, 30 Jun 2023 20:39:06 +0200 Message-ID: <20230630183908.32148-2-mkoutny@suse.com> X-Mailer: git-send-email 2.41.0 In-Reply-To: <20230630183908.32148-1-mkoutny@suse.com> References: <20230630183908.32148-1-mkoutny@suse.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-kselftest@vger.kernel.org When we migrate a task between two cgroups, one of the checks is a verification whether we can modify task's scheduler settings (cap_task_setscheduler()). An implicit migration occurs also when enabling a controller on the unified hierarchy (think of parent to child migration). The aforementioned check may be problematic if the caller of the migration (enabling a controller) has no permissions over migrated tasks. For instance, a user's cgroup that ends up running a process of a different user. Although cgroup permissions are configured favorably, the enablement fails due to the foreign process [1]. Change the behavior by relaxing the permissions check on the unified hierarchy (or in v2 mode). This is in accordance with unified hierarchy attachment behavior when permissions of the source to target cgroups are decisive whereas the migrated task is opaque (as opposed to more restrictive check in __cgroup1_procs_write()). [1] https://github.com/systemd/systemd/issues/18293#issuecomment-831205649 Signed-off-by: Michal Koutný --- kernel/cgroup/cpuset.c | 13 ++++++++++--- 1 file changed, 10 insertions(+), 3 deletions(-) diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c index 58e6f18f01c1..41d3ed14b0f4 100644 --- a/kernel/cgroup/cpuset.c +++ b/kernel/cgroup/cpuset.c @@ -2505,9 +2505,16 @@ static int cpuset_can_attach(struct cgroup_taskset *tset) ret = task_can_attach(task); if (ret) goto out_unlock; - ret = security_task_setscheduler(task); - if (ret) - goto out_unlock; + + /* + * Skip rights over task check in v2, migration permission derives + * from hierarchy ownership in cgroup_procs_write_permission()). + */ + if (!cgroup_subsys_on_dfl(cpuset_cgrp_subsys)) { + ret = security_task_setscheduler(task); + if (ret) + goto out_unlock; + } if (dl_task(task)) { cs->nr_migrate_dl_tasks++;