From patchwork Fri Sep 4 16:00:31 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: =?utf-8?q?Christian_G=C3=B6ttsche?= X-Patchwork-Id: 11757983 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id C60D3618 for ; Fri, 4 Sep 2020 16:01:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id AC08820796 for ; Fri, 4 Sep 2020 16:01:14 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=googlemail.com header.i=@googlemail.com header.b="q9BXhdl5" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727807AbgIDQBN (ORCPT ); Fri, 4 Sep 2020 12:01:13 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46240 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727075AbgIDQBB (ORCPT ); Fri, 4 Sep 2020 12:01:01 -0400 Received: from mail-ej1-x642.google.com (mail-ej1-x642.google.com [IPv6:2a00:1450:4864:20::642]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A3D4AC061244; Fri, 4 Sep 2020 09:01:00 -0700 (PDT) Received: by mail-ej1-x642.google.com with SMTP id j11so9381322ejk.0; Fri, 04 Sep 2020 09:01:00 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=googlemail.com; s=20161025; h=from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=BIz3Dqv9/KGHKChd3/IFzzxn7xbyzIDCFdjTQoSAu6w=; b=q9BXhdl5PVF9mLC9vkchxmULiG9xehyXT0Dy35pIMdBIVb2r4uf3zo0DYi5Uy4TT9g 8HtDMU8X3UsMUtmhW3jmB+GsLG784ov5aFIt3DdqsI6s7+pRgLhN3Hvl5mSOeUe8Ncfs RJx7BFIoShGkf/rkq2/jJ/tU5AZxegj5QRXv6XnnqIZZDSy1L0fVaJ8tabsEGyzNHoMd 2F/JQXKHQGqHSsl0Dx/uK6/36BJ6/onw/wG8iB9evJXvU+ZSreM5vc6/jHG72Y/lYhSh BfHjVKV7pCkdnSOdXA39mIocO3m/zYbismyZ/bLDTbpFwTYpEIcpLtHDtcX+hoi5JWnn u90g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=BIz3Dqv9/KGHKChd3/IFzzxn7xbyzIDCFdjTQoSAu6w=; b=LB4/YPPnngc7Y9X1m+iOqP7GhNYqTaLg5nhoI2undJ97rOYv+Eh3DpShc0YeztsMwK dCwutA/sNR8iifu2FMRTO7MTLFa8KTKC0FwECDLobqem/NsHJolM8dwnoy4h9XKV7hdJ WDeSe6oPOnsW2cLTGtQywGZszAnT1Dt5S6evcaLNdrudycjULxW3i+qdz0VDRfBF/6Kr o6kSGKbvhJXRZyj1tNaPEW3VoPkRheoizNCDZgvGbM6iI72sRQ7A50TY98NJnAfF7121 024CyqJePbevmUWvp7iKa6e8r0sRYSnWqNk7/2+d1kNZ5HjIHxknJOl0WbVkckGWBgTm BU1w== X-Gm-Message-State: AOAM5329+RV75/spu9Ect5uVJK/ctlGjW6DP4Mr0S6c39frOZ6oOxjFQ kdECx9u47A7bfv9++Mot8hiLKuQSMZ0CXSxH X-Google-Smtp-Source: ABdhPJz3Q8w4Tv7USQ8eui4LVCy5y4lAuTULMivw04dlU/rjS5/aBfLukg0LJ56MBQC+0SmUli78/Q== X-Received: by 2002:a17:906:5a83:: with SMTP id l3mr8552049ejq.14.1599235259141; Fri, 04 Sep 2020 09:00:59 -0700 (PDT) Received: from debianHome.localdomain (x5f700e02.dyn.telefonica.de. [95.112.14.2]) by smtp.gmail.com with ESMTPSA id h10sm6276025eds.0.2020.09.04.09.00.58 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 04 Sep 2020 09:00:58 -0700 (PDT) From: =?utf-8?q?Christian_G=C3=B6ttsche?= To: linux-kernel@vger.kernel.org Cc: selinux@vger.kernel.org, linux-security-module@vger.kernel.org, Ingo Molnar , Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman Subject: [RFC PATCH] sched: only issue an audit on privileged operation Date: Fri, 4 Sep 2020 18:00:31 +0200 Message-Id: <20200904160031.6444-1-cgzones@googlemail.com> X-Mailer: git-send-email 2.28.0 MIME-Version: 1.0 Sender: owner-linux-security-module@vger.kernel.org Precedence: bulk List-ID: sched_setattr(2) does via kernel/sched/core.c:__sched_setscheduler() issue a CAP_SYS_NICE audit event unconditionally, even when the requested operation does not require that capability / is un-privileged. Perform privilged/unprivileged catigorization first and perform a capable test only if needed. Signed-off-by: Christian Göttsche --- kernel/sched/core.c | 65 ++++++++++++++++++++++++++++++++------------- 1 file changed, 47 insertions(+), 18 deletions(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 8471a0f7eb32..954f968d2466 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -5249,13 +5249,19 @@ static int __sched_setscheduler(struct task_struct *p, return -EINVAL; /* - * Allow unprivileged RT tasks to decrease priority: + * Allow unprivileged RT tasks to decrease priority. + * Only issue a capable test if needed to avoid audit + * event on non-privileged operations: */ - if (user && !capable(CAP_SYS_NICE)) { + if (user) { if (fair_policy(policy)) { if (attr->sched_nice < task_nice(p) && - !can_nice(p, attr->sched_nice)) - return -EPERM; + !can_nice(p, attr->sched_nice)) { + if (capable(CAP_SYS_NICE)) + goto sys_nice_capable; + else + return -EPERM; + } } if (rt_policy(policy)) { @@ -5263,13 +5269,21 @@ static int __sched_setscheduler(struct task_struct *p, task_rlimit(p, RLIMIT_RTPRIO); /* Can't set/change the rt policy: */ - if (policy != p->policy && !rlim_rtprio) - return -EPERM; + if (policy != p->policy && !rlim_rtprio) { + if (capable(CAP_SYS_NICE)) + goto sys_nice_capable; + else + return -EPERM; + } /* Can't increase priority: */ if (attr->sched_priority > p->rt_priority && - attr->sched_priority > rlim_rtprio) - return -EPERM; + attr->sched_priority > rlim_rtprio) { + if (capable(CAP_SYS_NICE)) + goto sys_nice_capable; + else + return -EPERM; + } } /* @@ -5278,28 +5292,43 @@ static int __sched_setscheduler(struct task_struct *p, * unprivileged DL tasks to increase their relative deadline * or reduce their runtime (both ways reducing utilization) */ - if (dl_policy(policy)) - return -EPERM; + if (dl_policy(policy)) { + if (capable(CAP_SYS_NICE)) + goto sys_nice_capable; + else + return -EPERM; + } /* * Treat SCHED_IDLE as nice 20. Only allow a switch to * SCHED_NORMAL if the RLIMIT_NICE would normally permit it. */ if (task_has_idle_policy(p) && !idle_policy(policy)) { - if (!can_nice(p, task_nice(p))) - return -EPERM; + if (!can_nice(p, task_nice(p))) { + if (capable(CAP_SYS_NICE)) + goto sys_nice_capable; + else + return -EPERM; + } } /* Can't change other user's priorities: */ - if (!check_same_owner(p)) - return -EPERM; + if (!check_same_owner(p)) { + if (capable(CAP_SYS_NICE)) + goto sys_nice_capable; + else + return -EPERM; + } /* Normal users shall not reset the sched_reset_on_fork flag: */ - if (p->sched_reset_on_fork && !reset_on_fork) - return -EPERM; - } + if (p->sched_reset_on_fork && !reset_on_fork) { + if (capable(CAP_SYS_NICE)) + goto sys_nice_capable; + else + return -EPERM; + } - if (user) { +sys_nice_capable: if (attr->sched_flags & SCHED_FLAG_SUGOV) return -EINVAL;