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=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS 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 38F4BC43441 for ; Mon, 12 Nov 2018 01:53:57 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id DD83F208A3 for ; Mon, 12 Nov 2018 01:53:56 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org DD83F208A3 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=goodmis.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 S1730194AbeKLLop (ORCPT ); Mon, 12 Nov 2018 06:44:45 -0500 Received: from mail.kernel.org ([198.145.29.99]:40484 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729911AbeKLLop (ORCPT ); Mon, 12 Nov 2018 06:44:45 -0500 Received: from vmware.local.home (unknown [64.114.255.114]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 9AC1B2087F; Mon, 12 Nov 2018 01:53:54 +0000 (UTC) Date: Sun, 11 Nov 2018 20:53:51 -0500 From: Steven Rostedt To: Alexander Popov Cc: kernel-hardening@lists.openwall.com, Kees Cook , Jann Horn , Ingo Molnar , Andy Lutomirski , Joerg Roedel , Borislav Petkov , Thomas Gleixner , Dave Hansen , Peter Zijlstra , Jan Kara , Mathieu Desnoyers , Dan Williams , Masahiro Yamada , Masami Hiramatsu , x86@kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/1] stackleak: Disable ftrace for stackleak.c Message-ID: <20181111205351.1874bb1e@vmware.local.home> In-Reply-To: References: <1541887530-16610-1-git-send-email-alex.popov@linux.com> <20181110183011.2290fc20@gandalf.local.home> X-Mailer: Claws Mail 3.15.1 (GTK+ 2.24.32; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, 11 Nov 2018 13:19:45 +0300 Alexander Popov wrote: > On 11.11.2018 2:30, Steven Rostedt wrote: > > On Sun, 11 Nov 2018 01:05:30 +0300 > > Alexander Popov wrote: > > > >> The stackleak_erase() function is called on the trampoline stack at the > >> end of syscall. This stack is not big enough for ftrace operations, > >> e.g. it can be overflowed if we enable kprobe_events for stackleak_erase(). > > > > Is the issue with kprobes or with function tracing? Because this stops > > function tracing which I only want disabled if function tracing itself > > is an issue, not for other things that may use the function tracing > > infrastructure. > > Hello Steven, > > I believe that stackleak erasing is not compatible with function tracing itself. > That's what the kernel testing robot has hit: > https://www.openwall.com/lists/kernel-hardening/2018/11/09/1 > > I used kprobe_events just to reproduce the problem: > https://www.openwall.com/lists/kernel-hardening/2018/11/09/4 Have you tried adding a "notrace" to stackleak_erase()? Not tracing the entire file is a bit of overkill. There's no reason ftrace can't trace stack_erasing_sysctl() or perhaps even stackleak_track_stack() as that may be very interesting to trace. -- Steve