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=-2.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT 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 926FFC04AA7 for ; Tue, 14 May 2019 02:07:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 638762085A for ; Tue, 14 May 2019 02:07:36 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="gDzV41z7" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726680AbfENCHf (ORCPT ); Mon, 13 May 2019 22:07:35 -0400 Received: from mail-pl1-f195.google.com ([209.85.214.195]:42941 "EHLO mail-pl1-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726327AbfENCHf (ORCPT ); Mon, 13 May 2019 22:07:35 -0400 Received: by mail-pl1-f195.google.com with SMTP id x15so7389940pln.9; Mon, 13 May 2019 19:07:34 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=TUW58sFUl5sYOk3396X1MJdln3VeH0EXozxImmU59vw=; b=gDzV41z701QnCrQ26V0bq4z6xWTHENKXtePpErSx1cTFZAEnR170Cb3GIh6X6MaWvS P86mF/lBRPJUDD0wchUSehkIB5xvrpeuqlBa3x2Vho248Nn/RkVDrf1bXASF+h6UKMN4 RJw+91n48gNTDuIgc4nbPEe+W1cxRXTb+DWKeIovw8s8/EnknXE17L/40Sd6A2Ubbr5c mWCcTIy0CdYWj6taw53+CmqUKawbwZcEhJArjMmEt6X9vDDg49TOvQtWuiBMVFdi+mON IPNk5ELNC1d9yajDGEoP1a7uD/eSigryhXScvyM69k3K7CMtduUWmvSmvMIQ6zmk60J0 pPcA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=TUW58sFUl5sYOk3396X1MJdln3VeH0EXozxImmU59vw=; b=OQXl/Ci0QDUwGmKmNrDFYUJTh+xKTkbDdO/K8RHRF3J8ccuola8H9M8lORL5vCvmby AL6SP7t760ZYIajguGOoMoRZEAgGAAy2lgfEy5rRNHOAI9Cp9MGNdSKCzNtdIW95pbo1 hmKz/4DdnnSmXTtIOy47PCrbbV/aDMGYpTgJHsB+24fV62hpO7h/ayZ+hxyv3Th8A0oS qFxgmnWZQdqHhDTrfKCU5I1KuDmO6ADOcMWyx85fqT8bdhIW09gsKIoLugaFXxCEgXjJ m1UIizGv1sNmTpWwCOXiJyySqCQjh029Q5wWo9c4kKocvsuCK16dwRZ2+wGc9dUgNe8L Z7mw== X-Gm-Message-State: APjAAAXYuEx1TTifdK+TLYFbepgfkJ0cYCKzxslQC+6+Y4ixXft3i/xi 5kbk6GwLJPO/wmepgsizJhs= X-Google-Smtp-Source: APXvYqyCY0Kzi1kXb0vmv87aGVQQILnCJJ8qRJqL49F8s8Dds7JPB7O9ESBZIffOVdyOAeqexsF5/w== X-Received: by 2002:a17:902:108a:: with SMTP id c10mr35439629pla.48.1557799654316; Mon, 13 May 2019 19:07:34 -0700 (PDT) Received: from localhost ([39.7.55.172]) by smtp.gmail.com with ESMTPSA id v64sm19993908pfv.106.2019.05.13.19.07.32 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Mon, 13 May 2019 19:07:33 -0700 (PDT) Date: Tue, 14 May 2019 11:07:30 +0900 From: Sergey Senozhatsky To: Petr Mladek Cc: Andy Shevchenko , David Laight , 'christophe leroy' , Steven Rostedt , Linus Torvalds , Rasmus Villemoes , "Tobin C . Harding" , Michal Hocko , Sergey Senozhatsky , Sergey Senozhatsky , "linux-kernel@vger.kernel.org" , Michael Ellerman , "linuxppc-dev@lists.ozlabs.org" , Russell Currey , Stephen Rothwell , Heiko Carstens , "linux-arch@vger.kernel.org" , "linux-s390@vger.kernel.org" , Martin Schwidefsky Subject: Re: [PATCH] vsprintf: Do not break early boot with probing addresses Message-ID: <20190514020730.GA651@jagdpanzerIV> References: <20190510081635.GA4533@jagdpanzerIV> <20190510084213.22149-1-pmladek@suse.com> <20190510122401.21a598f6@gandalf.local.home> <096d6c9c17b3484484d9d9d3f3aa3a7c@AcuMS.aculab.com> <20190513091320.GK9224@smile.fi.intel.com> <20190513124220.wty2qbnz4wo52h3x@pathway.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190513124220.wty2qbnz4wo52h3x@pathway.suse.cz> User-Agent: Mutt/1.11.4 (2019-03-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On (05/13/19 14:42), Petr Mladek wrote: > > The "(null)" is good enough by itself and already an established > > practice.. > > (efault) made more sense with the probe_kernel_read() that > checked wide range of addresses. Well, I still think that > it makes sense to distinguish a pure NULL. And it still > used also for IS_ERR_VALUE(). Wouldn't anything within first PAGE_SIZE bytes be reported as a NULL deref? char *p = (char *)(PAGE_SIZE - 2); *p = 'a'; gives kernel: BUG: kernel NULL pointer dereference, address = 0000000000000ffe kernel: #PF: supervisor-privileged write access from kernel code kernel: #PF: error_code(0x0002) - not-present page And I like Steven's "(fault)" idea. How about this: if ptr < PAGE_SIZE -> "(null)" if IS_ERR_VALUE(ptr) -> "(fault)" -ss