From patchwork Fri Jan 29 19:05:10 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Sai Prakash Ranjan X-Patchwork-Id: 373837 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-16.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER, INCLUDES_PATCH, MAILING_LIST_MULTI, SPF_HELO_NONE, SPF_PASS, URIBL_BLOCKED, USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3AA3EC433DB for ; Fri, 29 Jan 2021 19:07:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 02D8A64E0B for ; Fri, 29 Jan 2021 19:07:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232681AbhA2THZ (ORCPT ); Fri, 29 Jan 2021 14:07:25 -0500 Received: from m42-8.mailgun.net ([69.72.42.8]:40484 "EHLO m42-8.mailgun.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232971AbhA2TGp (ORCPT ); Fri, 29 Jan 2021 14:06:45 -0500 DKIM-Signature: a=rsa-sha256; v=1; c=relaxed/relaxed; d=mg.codeaurora.org; q=dns/txt; s=smtp; t=1611947178; h=Content-Transfer-Encoding: MIME-Version: References: In-Reply-To: Message-Id: Date: Subject: Cc: To: From: Sender; bh=ANvyaZfiudWjkHRRQ6nes+pa/rluHPq6WULZ8ERI6Eg=; b=RYHauocghKlVevW1poj5Un//anFvKEejisTL0AZ/gjuxvsH+Ks6u2B+cneSaFHrcJgBq6da+ glT37Y9a6/AN4Pay42PlCqEeSnhX1PUCG7tH9Ca6QqvA9Ry/xUeeqECqT4nZpSz/BqSUN1hp Gt1qSDEDUpH7/QPG+grbCTu8Lz0= X-Mailgun-Sending-Ip: 69.72.42.8 X-Mailgun-Sid: WyI1MzIzYiIsICJsaW51eC1hcm0tbXNtQHZnZXIua2VybmVsLm9yZyIsICJiZTllNGEiXQ== Received: from smtp.codeaurora.org (ec2-35-166-182-171.us-west-2.compute.amazonaws.com [35.166.182.171]) by smtp-out-n06.prod.us-east-1.postgun.com with SMTP id 60145c848f2d32c2c57cf414 (version=TLS1.2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256); Fri, 29 Jan 2021 19:05:40 GMT Sender: saiprakash.ranjan=codeaurora.org@mg.codeaurora.org Received: by smtp.codeaurora.org (Postfix, from userid 1001) id 7F47DC43464; Fri, 29 Jan 2021 19:05:39 +0000 (UTC) Received: from blr-ubuntu-253.qualcomm.com (blr-bdr-fw-01_GlobalNAT_AllZones-Outside.qualcomm.com [103.229.18.19]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-SHA256 (128/128 bits)) (No client certificate requested) (Authenticated sender: saiprakash.ranjan) by smtp.codeaurora.org (Postfix) with ESMTPSA id 8AC1EC433CA; Fri, 29 Jan 2021 19:05:32 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 smtp.codeaurora.org 8AC1EC433CA Authentication-Results: aws-us-west-2-caf-mail-1.web.codeaurora.org; dmarc=none (p=none dis=none) header.from=codeaurora.org Authentication-Results: aws-us-west-2-caf-mail-1.web.codeaurora.org; spf=fail smtp.mailfrom=saiprakash.ranjan@codeaurora.org From: Sai Prakash Ranjan To: Mathieu Poirier , Suzuki K Poulose , Mike Leach , Peter Zijlstra , Ingo Molnar , Arnaldo Carvalho de Melo , Mark Rutland , Alexander Shishkin , Jiri Olsa , Namhyung Kim , Leo Yan Cc: coresight@lists.linaro.org, Stephen Boyd , Denis Nikitin , Mattias Nissler , Al Grant , linux-arm-msm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Sai Prakash Ranjan Subject: [PATCH 1/4] perf/core: Add support to exclude kernel mode instruction tracing Date: Sat, 30 Jan 2021 00:35:10 +0530 Message-Id: <89c7ff59d887a0360434e607bd625393ec3190e5.1611909025.git.saiprakash.ranjan@codeaurora.org> X-Mailer: git-send-email 2.29.0 In-Reply-To: References: MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-arm-msm@vger.kernel.org Hardware assisted tracing families such as ARM Coresight, Intel PT provides rich tracing capabilities including instruction level tracing and accurate timestamps which are very useful for profiling and also pose a significant security risk. One such example of security risk is when kernel mode tracing is not excluded and these hardware assisted tracing can be used to analyze cryptographic code execution. In this case, even the root user must not be able to infer anything. To explain it more clearly in the words of a security team member (credits: Mattias Nissler), "Consider a system where disk contents are encrypted and the encryption key is set up by the user when mounting the file system. From that point on the encryption key resides in the kernel. It seems reasonable to expect that the disk encryption key be protected from exfiltration even if the system later suffers a root compromise (or even against insiders that have root access), at least as long as the attacker doesn't manage to compromise the kernel." Here the idea is to protect such important information from all users including root users since root privileges does not have to mean full control over the kernel [1] and root compromise does not have to be the end of the world. Currently we can exclude kernel mode tracing via perf_event_paranoid sysctl but it has following limitations, * It is applicable to all PMUs and not just the ones supporting instruction tracing. * No option to restrict kernel mode instruction tracing by the root user. * Not possible to restrict kernel mode instruction tracing when the hardware assisted tracing IPs like ARM Coresight ETMs use an additional interface via sysfs for tracing in addition to perf interface. So introduce a new config CONFIG_EXCLUDE_KERNEL_HW_ITRACE to exclude kernel mode instruction tracing which will be generic and applicable to all hardware tracing families and which can also be used with other interfaces like sysfs in case of ETMs. [1] https://lwn.net/Articles/796866/ Suggested-by: Suzuki K Poulose Suggested-by: Al Grant Tested-by: Denis Nikitin Link: https://lore.kernel.org/lkml/20201015124522.1876-1-saiprakash.ranjan@codeaurora.org/ Signed-off-by: Sai Prakash Ranjan --- init/Kconfig | 12 ++++++++++++ kernel/events/core.c | 6 ++++++ 2 files changed, 18 insertions(+) diff --git a/init/Kconfig b/init/Kconfig index af454a51f3c5..31b4d1f26bce 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -1832,6 +1832,18 @@ config DEBUG_PERF_USE_VMALLOC endmenu +config EXCLUDE_KERNEL_HW_ITRACE + bool "Exclude kernel mode hardware assisted instruction tracing" + depends on PERF_EVENTS + help + Exclude kernel mode instruction tracing by hardware tracing + family such as ARM Coresight ETM, Intel PT and so on. + + This option allows to disable kernel mode instruction tracing + offered by hardware assisted tracing for all users(including root) + especially for production systems where only userspace tracing might + be preferred for security reasons. + config VM_EVENT_COUNTERS default y bool "Enable VM event counters for /proc/vmstat" if EXPERT diff --git a/kernel/events/core.c b/kernel/events/core.c index aece2fe19693..044a774cef6d 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -11866,6 +11866,12 @@ SYSCALL_DEFINE5(perf_event_open, goto err_task; } + if (IS_ENABLED(CONFIG_EXCLUDE_KERNEL_HW_ITRACE) && + (event->pmu->capabilities & PERF_PMU_CAP_ITRACE) && !attr.exclude_kernel) { + err = -EACCES; + goto err_alloc; + } + if (is_sampling_event(event)) { if (event->pmu->capabilities & PERF_PMU_CAP_NO_INTERRUPT) { err = -EOPNOTSUPP;