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=-2.4 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,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 369FEC4BA0E for ; Wed, 26 Feb 2020 11:18:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 002D424685 for ; Wed, 26 Feb 2020 11:18:35 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=alien8.de header.i=@alien8.de header.b="d4tmsZnw" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728042AbgBZLSe (ORCPT ); Wed, 26 Feb 2020 06:18:34 -0500 Received: from mail.skyhub.de ([5.9.137.197]:51638 "EHLO mail.skyhub.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726555AbgBZLSe (ORCPT ); Wed, 26 Feb 2020 06:18:34 -0500 Received: from zn.tnic (p200300EC2F08E300B4442D161B607307.dip0.t-ipconnect.de [IPv6:2003:ec:2f08:e300:b444:2d16:1b60:7307]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.skyhub.de (SuperMail on ZX Spectrum 128k) with ESMTPSA id 3C8441EC0CE8; Wed, 26 Feb 2020 12:18:33 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=alien8.de; s=dkim; t=1582715913; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:in-reply-to:in-reply-to: references:references; bh=A6vGW6WUZ5u5dkVwvmxhlqIwrUUQElMkiVyfzpmoYNE=; b=d4tmsZnwpqQRbWbXWbISqx/ToV3X/lDxjhdVx25tGVKzjZ6pF8Ga0vbGPlnafNAcqQPs/v vUpXL/JJr6kqLKoZtMRTzjy1ku7xqROLqmGS3++KsmpjO4ZwQr8oUPCMW49baleRd0f6Nk muU+bgepnGz0RQAIOefZOitsE2uN1aw= Date: Wed, 26 Feb 2020 12:18:27 +0100 From: Borislav Petkov To: Thomas Gleixner Cc: LKML , x86@kernel.org, Steven Rostedt , Brian Gerst , Juergen Gross , Paolo Bonzini , Arnd Bergmann , Andy Lutomirski Subject: Re: [patch 02/10] x86/mce: Disable tracing and kprobes on do_machine_check() Message-ID: <20200226111827.GA16756@zn.tnic> References: <20200225213636.689276920@linutronix.de> <20200225220216.315548935@linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20200225220216.315548935@linutronix.de> 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, Feb 25, 2020 at 10:36:38PM +0100, Thomas Gleixner wrote: > --- a/arch/x86/kernel/cpu/mce/core.c > +++ b/arch/x86/kernel/cpu/mce/core.c > @@ -1213,8 +1213,14 @@ static void __mc_scan_banks(struct mce * > * On Intel systems this is entered on all CPUs in parallel through > * MCE broadcast. However some CPUs might be broken beyond repair, > * so be always careful when synchronizing with others. > + * > + * Tracing and kprobes are disabled: if we interrupted a kernel context > + * with IF=1, we need to minimize stack usage. There are also recursion > + * issues: if the machine check was due to a failure of the memory > + * backing the user stack, tracing that reads the user stack will cause ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Had to read this a couple of times to parse that formulation properly. Make that "... backing the user stack, tracing code which accesses same user stack will potentially cause an infinite recursion." With that: Reviewed-by: Borislav Petkov Thx. -- Regards/Gruss, Boris. https://people.kernel.org/tglx/notes-about-netiquette