From mboxrd@z Thu Jan 1 00:00:00 1970 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=-26.6 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_GIT,USER_IN_DEF_DKIM_WL autolearn=unavailable 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 B2F3AC43381 for ; Fri, 8 Jan 2021 21:00:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 91E1A23A7F for ; Fri, 8 Jan 2021 21:00:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727845AbhAHVAL (ORCPT ); Fri, 8 Jan 2021 16:00:11 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59368 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727003AbhAHVAK (ORCPT ); Fri, 8 Jan 2021 16:00:10 -0500 Received: from mail-qv1-xf4a.google.com (mail-qv1-xf4a.google.com [IPv6:2607:f8b0:4864:20::f4a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 06880C061757 for ; Fri, 8 Jan 2021 12:59:03 -0800 (PST) Received: by mail-qv1-xf4a.google.com with SMTP id t18so9112768qva.6 for ; Fri, 08 Jan 2021 12:59:02 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=sender:date:message-id:mime-version:subject:from:to:cc; bh=pg2+obVmDdZw2cVJ7QAMiVijjbCTy6dUmk2h4J5JypM=; b=bGwlBNOlqsBerbH0/KNUcpimkFnfnQdqlYIwG/BNL3IRka1C9Q54SMbgiR+Ihs0Qqf PBF2zL6u4tLZSFtNLHF1Y0SodUbYkNODtyJVn/SXmybjq9qupbwXkiNw8G5ljf6WIAt8 /901fZEST9OlaVA/TLox3tLuLqNOXg2+Gzuh5jXpQBI3rTiltYyjnxEjs7Oe1mrK7Wn8 fnmaaRZKXRRVIOYHKaOXzCtrgHfvIEtCkST1wmua8yZ4JAe0h2Gq+ChYdP0EE4/76B7x nVdrfwoVbCqshvN6rbO9uFv5X4iQBwH5vAK+6sepxIIXUWCfOjOkubfSgSBhLwaFeQHh m9OQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:sender:date:message-id:mime-version:subject:from :to:cc; bh=pg2+obVmDdZw2cVJ7QAMiVijjbCTy6dUmk2h4J5JypM=; b=tEbg2wQKP8PaQqdjP/R5CWTUWQn0V1LfWm8r5QYYOEWcDEsI1hUue/5oLfmvo7tcIr g5TlbQ1Dbl0ZHO0pfV9Oks6tFM3c/HfDF8e8Nhb2HujvixAnenoLSHCtKafoL9Gee74Q lMEFJJG2UkHkC1pcO7qGYmBgOQKIBKDzwOTtGWkYYIMgmfwaZMmOxZ8SjvavVjaXsR7J CZCVmDsPX51lAvlSd5Ib/xnDOnv6E2OkCoc6J4D7cMX0WL4hrABui7pLKZW4lOpUz2Ug WjBZRYylA7h86uanqhs5x52pfoBusjQEd7EstIktYyHT78E5lvX416VKbI2lzH6KqPJl 9rAA== X-Gm-Message-State: AOAM533VKifjN2QYfEnc52JwD+qSNZVbm4S/NgwFVsKTOr+jzR6ZLLyz 8xcpqz6rBiFZzuyInkBx3PBCGROA28k= X-Google-Smtp-Source: ABdhPJzkhcWm36Y5z3eQqRcs4DfyJUCy0+z8bCk7zQYdPc0oJNglTollph0feYqWo91RO0orZmPxFLLqhs4= Sender: "surenb via sendgmr" X-Received: from surenb1.mtv.corp.google.com ([100.98.240.136]) (user=surenb job=sendgmr) by 2002:ad4:4888:: with SMTP id bv8mr5409095qvb.0.1610139542143; Fri, 08 Jan 2021 12:59:02 -0800 (PST) Date: Fri, 8 Jan 2021 12:58:57 -0800 Message-Id: <20210108205857.1471269-1-surenb@google.com> Mime-Version: 1.0 X-Mailer: git-send-email 2.30.0.284.gd98b1dd5eaa7-goog Subject: [PATCH 1/1] mm/madvise: replace ptrace attach requirement for process_madvise From: Suren Baghdasaryan To: akpm@linux-foundation.org Cc: jannh@google.com, keescook@chromium.org, jeffv@google.com, minchan@kernel.org, mhocko@suse.com, shakeelb@google.com, rientjes@google.com, edgararriaga@google.com, timmurray@google.com, linux-mm@kvack.org, selinux@vger.kernel.org, linux-api@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-team@android.com, surenb@google.com Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-api@vger.kernel.org process_madvise currently requires ptrace attach capability. PTRACE_MODE_ATTACH gives one process complete control over another process. It effectively removes the security boundary between the two processes (in one direction). Granting ptrace attach capability even to a system process is considered dangerous since it creates an attack surface. This severely limits the usage of this API. The operations process_madvise can perform do not affect the correctness of the operation of the target process; they only affect where the data is physically located (and therefore, how fast it can be accessed). What we want is the ability for one process to influence another process in order to optimize performance across the entire system while leaving the security boundary intact. Replace PTRACE_MODE_ATTACH with a combination of PTRACE_MODE_READ and CAP_SYS_NICE. PTRACE_MODE_READ to prevent leaking ASLR metadata and CAP_SYS_NICE for influencing process performance. Signed-off-by: Suren Baghdasaryan --- mm/madvise.c | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-) diff --git a/mm/madvise.c b/mm/madvise.c index 6a660858784b..c2d600386902 100644 --- a/mm/madvise.c +++ b/mm/madvise.c @@ -1197,12 +1197,22 @@ SYSCALL_DEFINE5(process_madvise, int, pidfd, const struct iovec __user *, vec, goto release_task; } - mm = mm_access(task, PTRACE_MODE_ATTACH_FSCREDS); + /* Require PTRACE_MODE_READ to avoid leaking ASLR metadata. */ + mm = mm_access(task, PTRACE_MODE_READ_FSCREDS); if (IS_ERR_OR_NULL(mm)) { ret = IS_ERR(mm) ? PTR_ERR(mm) : -ESRCH; goto release_task; } + /* + * Require CAP_SYS_NICE for influencing process performance. Note that + * only non-destructive hints are currently supported. + */ + if (!capable(CAP_SYS_NICE)) { + ret = -EPERM; + goto release_task; + } + total_len = iov_iter_count(&iter); while (iov_iter_count(&iter)) { -- 2.30.0.284.gd98b1dd5eaa7-goog