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=-5.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS 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 9587EC433ED for ; Wed, 7 Apr 2021 21:18:23 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id D30CB61107 for ; Wed, 7 Apr 2021 21:18:22 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D30CB61107 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=alien8.de Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 3EFB36B0073; Wed, 7 Apr 2021 17:18:22 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 39FB16B0078; Wed, 7 Apr 2021 17:18:22 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 265F26B007D; Wed, 7 Apr 2021 17:18:22 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0193.hostedemail.com [216.40.44.193]) by kanga.kvack.org (Postfix) with ESMTP id 08CE76B0073 for ; Wed, 7 Apr 2021 17:18:22 -0400 (EDT) Received: from smtpin33.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id A9DC2824805A for ; Wed, 7 Apr 2021 21:18:21 +0000 (UTC) X-FDA: 78006834402.33.1100BCE Received: from mail.skyhub.de (mail.skyhub.de [5.9.137.197]) by imf22.hostedemail.com (Postfix) with ESMTP id C916BC0007C0 for ; Wed, 7 Apr 2021 21:18:18 +0000 (UTC) Received: from zn.tnic (p200300ec2f08fb0020f55c189e926593.dip0.t-ipconnect.de [IPv6:2003:ec:2f08:fb00:20f5:5c18:9e92:6593]) (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 DEDB71EC0345; Wed, 7 Apr 2021 23:18:17 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=alien8.de; s=dkim; t=1617830298; 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=lR4HjhpfT7Q4Vo+Wt3lVbKX5Wx7rTwYicT74GM2+xNI=; b=GbyN1jVATBLorJv4BVyplZeZdx3/XUSg8LeGrAB5RfCI2sWwIRwYZou8M40d1lL2/VQWpY /V/p/bBwRY2bw/6nwMfYuJVCQLszUG6jLFieqeuGTO1exSKHEcuyqSc2Dfu+QEN7Gg+2FM vTAysXYGeqakxS/nZOii94xTguM58+8= Date: Wed, 7 Apr 2021 23:18:16 +0200 From: Borislav Petkov To: Tony Luck Cc: x86@kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Andy Lutomirski , Aili Yao , HORIGUCHI =?utf-8?B?TkFPWUEoIOWggOWPo+OAgOebtOS5nyk=?= Subject: Re: [PATCH 3/4] mce/copyin: fix to not SIGBUS when copying from user hits poison Message-ID: <20210407211816.GP25319@zn.tnic> References: <20210326000235.370514-1-tony.luck@intel.com> <20210326000235.370514-4-tony.luck@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20210326000235.370514-4-tony.luck@intel.com> X-Stat-Signature: 5pp99z8t8m84rmjon3wypsigd3wxn8ox X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: C916BC0007C0 Received-SPF: none (alien8.de>: No applicable sender policy available) receiver=imf22; identity=mailfrom; envelope-from=""; helo=mail.skyhub.de; client-ip=5.9.137.197 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1617830298-306268 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Thu, Mar 25, 2021 at 05:02:34PM -0700, Tony Luck wrote: > Andy Lutomirski pointed out that sending SIGBUS to tasks that > hit poison in the kernel copying syscall parameters from user > address space is not the right semantic. What does that mean exactly? >From looking at the code, that is this conditional: if (t == EX_HANDLER_UACCESS && regs && is_copy_from_user(regs)) { m->kflags |= MCE_IN_KERNEL_RECOV; m->kflags |= MCE_IN_KERNEL_COPYIN; so what does the above have to do with syscall params? If it is about us being in ring 0 and touching user memory and eating poison in same *user* memory while doing so, then sure, that makes sense. > So stop doing that. Add a new kill_me_never() call back that > simply unmaps and offlines the poison page. Right, that's the same as handling poisoned user memory. Thx. -- Regards/Gruss, Boris. https://people.kernel.org/tglx/notes-about-netiquette