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=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_2 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 EAA75C06510 for ; Tue, 2 Jul 2019 15:34:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C23282173E for ; Tue, 2 Jul 2019 15:34:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726483AbfGBPd7 (ORCPT ); Tue, 2 Jul 2019 11:33:59 -0400 Received: from mail.kernel.org ([198.145.29.99]:58088 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725780AbfGBPd7 (ORCPT ); Tue, 2 Jul 2019 11:33:59 -0400 Received: from gandalf.local.home (cpe-66-24-58-225.stny.res.rr.com [66.24.58.225]) (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 AD473206A3; Tue, 2 Jul 2019 15:33:57 +0000 (UTC) Date: Tue, 2 Jul 2019 11:33:55 -0400 From: Steven Rostedt To: Thomas Gleixner Cc: Peter Zijlstra , Eiichi Tsukata , edwintorok@gmail.com, mingo@redhat.com, bp@alien8.de, hpa@zytor.com, x86@kernel.org, linux-kernel@vger.kernel.org, Josh Poimboeuf Subject: Re: [PATCH] x86/stacktrace: Do not access user space memory unnecessarily Message-ID: <20190702113355.5be9ebfe@gandalf.local.home> In-Reply-To: References: <20190702053151.26922-1-devel@etsukata.com> <20190702072821.GX3419@hirez.programming.kicks-ass.net> X-Mailer: Claws Mail 3.17.3 (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 Tue, 2 Jul 2019 16:14:05 +0200 (CEST) Thomas Gleixner wrote: > On Tue, 2 Jul 2019, Peter Zijlstra wrote: > > > On Tue, Jul 02, 2019 at 02:31:51PM +0900, Eiichi Tsukata wrote: > > > Put the boundary check before it accesses user space to prevent unnecessary > > > access which might crash the machine. > > > > > > Especially, ftrace preemptirq/irq_disable event with user stack trace > > > option can trigger SEGV in pid 1 which leads to panic. Note, I'm only able to trigger this crash with the irq_disable event. The irq_enable and preempt_disable/enable events work just fine. This leads me to believe that the TRACE_IRQS_OFF macro (which uses a thunk trampoline) may have some issues and is probably the place to look at. -- Steve > > It triggers segfaults in random user processes which is bad enough. > > And even with that 'fix' applied I can see random segfaults just less > frequent. > > > > RIP: 0033:0x55be7ad1c89f > > > Code: Bad RIP value. > > > > ^^^ that's weird, no amount of unwinding should affect regs->ip. > >