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=-10.3 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_PASS,USER_AGENT_GIT,USER_IN_DEF_DKIM_WL 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 0DD3FC43334 for ; Thu, 6 Sep 2018 14:29:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A3D1A2075B for ; Thu, 6 Sep 2018 14:29:50 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="DEGQx61v" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A3D1A2075B Authentication-Results: mail.kernel.org; dmarc=fail (p=reject dis=none) header.from=google.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730000AbeIFTFg (ORCPT ); Thu, 6 Sep 2018 15:05:36 -0400 Received: from mail-vk0-f73.google.com ([209.85.213.73]:50384 "EHLO mail-vk0-f73.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729401AbeIFTFg (ORCPT ); Thu, 6 Sep 2018 15:05:36 -0400 Received: by mail-vk0-f73.google.com with SMTP id n135-v6so3772868vke.17 for ; Thu, 06 Sep 2018 07:29:47 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:message-id:mime-version:subject:from:to:cc; bh=HGp0kMaMTlvqs08pLn4mkIkxA0/YTHUf7uHJuW9/Rc4=; b=DEGQx61vVlvXh+p4JQPgROXPHEUUq0LMPlBYintVPzZvTmSzy1xW7qrgMLAF2ZqG1Q Pxft8Ihn5pfeAgU02fymYRzRByKTQ3KnMvhUZsruLJNWT/MevXbp1V17h7zQHqKKc9se H6YjcJDYcSNmnQLsFKap7OcU8zAY6uYwZ/drLRAOtDdoUFjMR5YH0XVHG3Xm59MNBCKV NBVaREj3JotndA5co4WLeQAo3D/Y0lTSNwrmw4/h88J7j8dhfXwivVtV1VkexQcfh1BG xLcYc9/FFVSBsiPR+Ike7n4Ctf0xnMUb7Ob+E/OCGbbR7naqiKICTaAqOf9uoUqiBP0r eUWg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:message-id:mime-version:subject:from:to:cc; bh=HGp0kMaMTlvqs08pLn4mkIkxA0/YTHUf7uHJuW9/Rc4=; b=MolaG0Yf5ESMkqyxhe5jwUFaOKg0CapAzY5gLfQ2y1UnbaaAMCdZN5hLXEKGmf6Vms 1t0rNhQ9tmMv6SghIbbDLsD/siVdIQiWi40yV3a/n6s4sEWrpMEyxADVgu0MbudEVSLz 1dIVCJTPo6P/T/2BPW7th6LymNShyNAAWwVPo2k76GgNDDAHP83mTFBYw/c43it5hiNr jb29SaOfti8ZDmA3LbzwFYWNsfuV9pVHJ8EwjHmZJjXMspmPVlMRvrXkxK/J32APuKQa GK7O6ASErF/zXOriQ42WogdWem/IVkzhwfRs04xqVpcGDnAv/9tBa6XjsjocEgczEMu3 5Qkw== X-Gm-Message-State: APzg51DJPmvPVYDBPnLFvZyy8s1XTflUopLQhGD5lgjVvK6yJKo6oHp1 GhifKB1lgjEfahs/WVbac9vym7Tc0Q== X-Google-Smtp-Source: ANB0Vdau57VrzvPf++Ee/9Fnqhs96uPWj13PUp4VLtiX7ev0BZ6uu3qlyaKPCXm/c8ToCPwv70vqy0CWsA== X-Received: by 2002:a1f:fe07:: with SMTP id l7-v6mr564096vki.59.1536244187306; Thu, 06 Sep 2018 07:29:47 -0700 (PDT) Date: Thu, 6 Sep 2018 16:29:35 +0200 Message-Id: <20180906142935.230597-1-jannh@google.com> Mime-Version: 1.0 X-Mailer: git-send-email 2.19.0.rc1.350.ge57e33dbd1-goog Subject: [PATCH] Yama: use READ_ONCE() when reading ptrace_scope From: Jann Horn To: Kees Cook , jannh@google.com Cc: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org ptrace_scope can be modified concurrently. To ensure that the compiler only reads ptrace_scope once, use READ_ONCE() here. (In practice, at least the version of gcc on my machine only generates a single read anyway, and it seems unlikely that a compiler would do something different.) This also serves as documentation for the reader. Signed-off-by: Jann Horn --- security/yama/yama_lsm.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/security/yama/yama_lsm.c b/security/yama/yama_lsm.c index ffda91a4a1aa..3b18e4455f53 100644 --- a/security/yama/yama_lsm.c +++ b/security/yama/yama_lsm.c @@ -362,7 +362,7 @@ static int yama_ptrace_access_check(struct task_struct *child, /* require ptrace target be a child of ptracer on attach */ if (mode & PTRACE_MODE_ATTACH) { - switch (ptrace_scope) { + switch (READ_ONCE(ptrace_scope)) { case YAMA_SCOPE_DISABLED: /* No additional restrictions. */ break; @@ -404,7 +404,7 @@ int yama_ptrace_traceme(struct task_struct *parent) int rc = 0; /* Only disallow PTRACE_TRACEME on more aggressive settings. */ - switch (ptrace_scope) { + switch (READ_ONCE(ptrace_scope)) { case YAMA_SCOPE_CAPABILITY: if (!has_ns_capability(parent, current_user_ns(), CAP_SYS_PTRACE)) rc = -EPERM; -- 2.19.0.rc1.350.ge57e33dbd1-goog