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,URIBL_BLOCKED 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 166CAC10F0E for ; Sun, 7 Apr 2019 22:44:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id DD90720880 for ; Sun, 7 Apr 2019 22:44:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726513AbfDGWoa (ORCPT ); Sun, 7 Apr 2019 18:44:30 -0400 Received: from Galois.linutronix.de ([146.0.238.70]:51040 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726366AbfDGWoa (ORCPT ); Sun, 7 Apr 2019 18:44:30 -0400 Received: from p5492ee6e.dip0.t-ipconnect.de ([84.146.238.110] helo=nanos) by Galois.linutronix.de with esmtpsa (TLS1.2:DHE_RSA_AES_256_CBC_SHA256:256) (Exim 4.80) (envelope-from ) id 1hDGWW-0004bB-LY; Mon, 08 Apr 2019 00:44:24 +0200 Date: Mon, 8 Apr 2019 00:44:24 +0200 (CEST) From: Thomas Gleixner To: Andy Lutomirski cc: LKML , X86 ML , Josh Poimboeuf , Sean Christopherson Subject: Re: [patch V2 28/29] x86/irq/64: Remap the IRQ stack with guard pages In-Reply-To: Message-ID: References: <20190405150658.237064784@linutronix.de> <20190405150930.967389183@linutronix.de> User-Agent: Alpine 2.21 (DEB 202 2017-01-01) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII X-Linutronix-Spam-Score: -1.0 X-Linutronix-Spam-Level: - X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required, ALL_TRUSTED=-1,SHORTCIRCUIT=-0.0001 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, 6 Apr 2019, Andy Lutomirski wrote: > On Fri, Apr 5, 2019 at 8:11 AM Thomas Gleixner wrote: > > > > From: Andy Lutomirski > > > > The IRQ stack lives in percpu space, so an IRQ handler that overflows it > > will overwrite other data structures. > > > > Use vmap() to remap the IRQ stack so that it will have the usual guard > > pages that vmap/vmalloc allocations have. With this the kernel will panic > > immediately on an IRQ stack overflow. > > The 0day bot noticed that this dies with DEBUG_PAGEALLOC on. This is > because the store_stackinfo() function is utter garbage and this patch > correctly detects just how broken it is. The attached patch "fixes" > it. (It also contains a reliability improvement that should probably > get folded in, but is otherwise unrelated.) > > A real fix would remove the generic kstack_end() function entirely > along with __HAVE_ARCH_KSTACK_END and would optionally replace > store_stackinfo() with something useful. Josh, do we have a generic > API to do a little stack walk like this? Otherwise, I don't think it > would be the end of the world to just remove the offending code. Actually we have: save_stack_trace()