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=-1.7 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,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 A2EEDC43441 for ; Mon, 12 Nov 2018 02:51:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 69EEE214DB for ; Mon, 12 Nov 2018 02:51:05 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="2L9sN0Kq" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 69EEE214DB Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.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 S1730359AbeKLMmG (ORCPT ); Mon, 12 Nov 2018 07:42:06 -0500 Received: from mail.kernel.org ([198.145.29.99]:49610 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730260AbeKLMmG (ORCPT ); Mon, 12 Nov 2018 07:42:06 -0500 Received: from devnote (NE2965lan1.rev.em-net.ne.jp [210.141.244.193]) (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 BE68120881; Mon, 12 Nov 2018 02:51:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1541991063; bh=8ZP9A9bYAHBJPDaWSaqzCqZIJ2bVA0w1izDTg1cOkdI=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=2L9sN0KqZH0YkM8jeYL/bs7dkmk0oNI7sNfszQxPMeo6cx42mTXkBHgrrF84VqCxB cdJyAjEXzEC+UB3PnIY20lz14qicPy63rEEjv1lNvKIoEcoNfDGR95Pf/rkS8Pq5Tr nOyP4FwXxng5mkEMgPNvw6h460Ridm1eCt6CNiPM= Date: Mon, 12 Nov 2018 11:50:58 +0900 From: Masami Hiramatsu To: Steven Rostedt Cc: Alexander Popov , 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: <20181112115058.39e98750750c91eeb349cfdf@kernel.org> In-Reply-To: <20181111205351.1874bb1e@vmware.local.home> References: <1541887530-16610-1-git-send-email-alex.popov@linux.com> <20181110183011.2290fc20@gandalf.local.home> <20181111205351.1874bb1e@vmware.local.home> X-Mailer: Sylpheed 3.5.0 (GTK+ 2.24.30; 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 Hi Alexander and Steve, On Sun, 11 Nov 2018 20:53:51 -0500 Steven Rostedt wrote: > 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. I think it is not enough for stopping kprobes. If you want to stop the kprobes (int3 version) on stackleak_erase(), you should use NOKPROBE_SYMBOL(stackleak_erase), since kprobes can work without ftrace. Thank you, -- Masami Hiramatsu