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=-2.0 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=no 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 ECA8BC7618B for ; Tue, 23 Jul 2019 15:14:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B9580218F0 for ; Tue, 23 Jul 2019 15:14:55 +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="JSZ6PnpI" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2390816AbfGWPOy (ORCPT ); Tue, 23 Jul 2019 11:14:54 -0400 Received: from bombadil.infradead.org ([198.137.202.133]:49566 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729358AbfGWPOx (ORCPT ); Tue, 23 Jul 2019 11:14:53 -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-Transfer-Encoding :Content-Type:MIME-Version:References:Message-ID:Subject:Cc:To:From:Date: Sender:Reply-To: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=ZQsVTPSDNSDkcFW9cXj3JbR5Y7NqzGJBRE1PkZOgQkU=; b=JSZ6PnpIJD6Tf8e+dQZEVPK9D+ NFsTUDdmiXl23ETstYe91SHCcUomsasfk9da7+u2KmA48gUfVpFRNjoPA6jHAeG7ZQt9myQrhsF14 g+E5B7n7wh83RWBc+DY60kRjreeRj2rbem4He4bvL5rSNgIsNvXkykj0Thyz9pxqBDsCEZVwynkBe XcCkqBKMPZkHGCY9lj3CmCPnQbCCVekvYrZ5v81f3DDBjZOT/bcpWoZwTFERELx8vCYK26HbD2ygw qlXNmFO63P+oXuCOAk+sJTP9xwVxkvKDDpUTNz5Exm0iZZNKy+nTVn8b/J4wQRg7IirMGjb+PjRPd MKNdUk7w==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=hirez.programming.kicks-ass.net) by bombadil.infradead.org with esmtpsa (Exim 4.92 #3 (Red Hat Linux)) id 1hpwV7-0000Q7-9p; Tue, 23 Jul 2019 15:14:49 +0000 Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 4A21A201A57EF; Tue, 23 Jul 2019 17:14:47 +0200 (CEST) Date: Tue, 23 Jul 2019 17:14:47 +0200 From: Peter Zijlstra To: Andy Lutomirski Cc: Andy Lutomirski , Kees Cook , Thomas Gleixner , Sean Christopherson , Vincenzo Frascino , X86 ML , LKML Subject: Re: [5.2 REGRESSION] Generic vDSO breaks seccomp-enabled userspace on i386 Message-ID: <20190723151447.GO3419@hirez.programming.kicks-ass.net> References: <20190719170343.GA13680@linux.intel.com> <19EF7AC8-609A-4E86-B45E-98DFE965DAAB@amacapital.net> <201907221012.41504DCD@keescook> <201907221135.2C2D262D8@keescook> <201907221620.F31B9A082@keescook> <20190723091820.GZ3402@hirez.programming.kicks-ass.net> <17F255F9-5084-4E30-9AD6-80A4F49BD0D8@amacapital.net> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <17F255F9-5084-4E30-9AD6-80A4F49BD0D8@amacapital.net> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jul 23, 2019 at 07:04:46AM -0700, Andy Lutomirski wrote: > > > > On Jul 23, 2019, at 2:18 AM, Peter Zijlstra wrote: > > > >> On Mon, Jul 22, 2019 at 04:47:36PM -0700, Andy Lutomirski wrote: > >> > >> I don't love this whole concept, but I also don't have a better idea. > > > > Are we really talking about changing the kernel because BPF is expecting > > things? That is, did we just elevate everything BPF can observe to ABI? > > > > No, this isn’t about internals in the kernel mode sense. *phew*, I was scared for a wee moment. > It’s about the smallish number of cases where the kernel causes user > code to do a specific syscall and the user has a policy that doesn’t > allow that syscall. This is visible to user code via seccomp and > ptrace. > > Yes, it’s obnoxious. Do you have any suggestions? Not really; I think I just demonstrated I don't fully understand the problem space here :/