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=-2.1 required=3.0 tests=DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,T_DKIM_INVALID, USER_AGENT_MUTT 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 E0034C433F5 for ; Mon, 3 Sep 2018 13:48:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 98D0E20658 for ; Mon, 3 Sep 2018 13:48:09 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="k684zhJz" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 98D0E20658 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org 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 S1727577AbeICSIX (ORCPT ); Mon, 3 Sep 2018 14:08:23 -0400 Received: from bombadil.infradead.org ([198.137.202.133]:52728 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725982AbeICSIW (ORCPT ); Mon, 3 Sep 2018 14:08:22 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=RSJ9dMuvOpV6mhRHhDgdBZefOdut6QN7XZKbtYPaL+M=; b=k684zhJzUVe99eTRGtqX9+9Um e4T+OZE8aPgZ2SEZ+JMxs4SD9VW9ygnqrLt6hjFSJp5RRpMpX8AS6rdY7rGkVT0RteW4656LpkuxE UBL4p492Jf7Vsqjv+Z06zh3MUpaHv/CGEUoelQNrvbuMPOV/jH34NAspFpaIdYScD9tkbe4X4Gr8/ eXoZUgo99If9uXBF1OJuShy8fxotYqLPz2bnPAKialLx6tOSsc5j82LN94upKE4fzWAivPhfO0nL2 LpOIWY3itFvHiRgeTobniUXIQvjoGPJ5h+XC57KU8btmb5w/XJ1IBMXdOX4UdBU0gzpyGvvRSKGvl VoTwWq9aw==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=hirez.programming.kicks-ass.net) by bombadil.infradead.org with esmtpsa (Exim 4.90_1 #2 (Red Hat Linux)) id 1fwpCr-0003Ku-8C; Mon, 03 Sep 2018 13:47:53 +0000 Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 36B3E2018FA29; Mon, 3 Sep 2018 15:47:51 +0200 (CEST) Date: Mon, 3 Sep 2018 15:47:51 +0200 From: Peter Zijlstra To: Jiri Kosina Cc: Thomas Gleixner , Ingo Molnar , Josh Poimboeuf , Andrea Arcangeli , "Woodhouse, David" , linux-kernel@vger.kernel.org, x86@kernel.org, Oleg Nesterov , Tim Chen Subject: Re: [PATCH v2 2/3] x86/speculation: Apply IBPB more strictly to avoid cross-process spectre v2 leak Message-ID: <20180903134751.GV24124@hirez.programming.kicks-ass.net> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.0 (2018-05-17) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Sep 03, 2018 at 02:45:25PM +0200, Jiri Kosina wrote: > if (tsk && tsk->mm && > tsk->mm->context.ctx_id != last_ctx_id && > - get_dumpable(tsk->mm) != SUID_DUMP_USER) > + ___ptrace_may_access(tsk, current, PTRACE_MODE_IBPB)) > indirect_branch_prediction_barrier(); So the question posed here is: can @next ptrace @prev? Which confuses me greatly; it is @prev doing the BTB poisoning for @next, so we want to know if @prev can ptrace @next, no?