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=-0.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,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 32AB2C43603 for ; Sat, 14 Dec 2019 07:55:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 07FD724658 for ; Sat, 14 Dec 2019 07:55:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1576310122; bh=37tV1SM+durbtVnc1SZJaIoQfBdJLToeVvqsv8IROTA=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=rXHA191UNdy3OR3jb0HPFYjSoTBkZ0jTVhIeqqdn1i2pvi2AuzqB7z6W3dPgn1EcE dKtX1OHeniaWrN8CKeL6p2pP5cWJwbybaqT5BUCZ8xkKTjWBqksBWEhHeXCY8ypgSf Xa4YJmEoT3ku9QHjUG5mcbpLcz3xCfCrSQgx5yAo= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725730AbfLNHzV (ORCPT ); Sat, 14 Dec 2019 02:55:21 -0500 Received: from mail.kernel.org ([198.145.29.99]:42112 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725851AbfLNHzV (ORCPT ); Sat, 14 Dec 2019 02:55:21 -0500 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (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 61B032073D; Sat, 14 Dec 2019 07:55:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1576310120; bh=37tV1SM+durbtVnc1SZJaIoQfBdJLToeVvqsv8IROTA=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=dKTe7f5Na3+7CLUnVjCF7EOhyTtJ2pHjUXEe1t4rQjsuuiBTBpGjFpR0aBBNv+Wkj LzeKZ0DvFcG2v5lwx1DsNU7xU1SxYalBvu68J8qcBh2xvNw/R0ac+0QzCiFbcrA3T0 JCAd9aZgMezJH5a9dZ186sq5sP9iFMaYN8FTU1D0= Date: Sat, 14 Dec 2019 08:55:17 +0100 From: Greg KH To: Tetsuo Handa Cc: Dmitry Vyukov , Linus Torvalds , syzbot , Andy Shevchenko , asierra@xes-inc.com, ext-kimmo.rautkoski@vaisala.com, Jiri Slaby , kai heng feng , LKML , linux-serial , mika.westerberg@linux.intel.com, o.barta89@gmail.com, paulburton@kernel.org, sr@denx.de, syzkaller-bugs , yegorslists@googlemail.com Subject: Re: BUG: unable to handle kernel NULL pointer dereference in mem_serial_out Message-ID: <20191214075517.GA3314866@kroah.com> References: <00000000000053539a0599173973@google.com> <20191212105701.GB1476206@kroah.com> <20191213093357.GB2135612@kroah.com> <74859736-478a-6ad7-f0be-cfe87ec40ff5@i-love.sakura.ne.jp> <20191213160700.GA2632926@kroah.com> <4f514a5a-af11-e688-8f8d-72bbadadc889@i-love.sakura.ne.jp> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4f514a5a-af11-e688-8f8d-72bbadadc889@i-love.sakura.ne.jp> Sender: linux-serial-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-serial@vger.kernel.org On Sat, Dec 14, 2019 at 09:48:29AM +0900, Tetsuo Handa wrote: > On 2019/12/14 1:07, Greg KH wrote: > > On Fri, Dec 13, 2019 at 11:31:08PM +0900, Tetsuo Handa wrote: > >> On 2019/12/13 19:00, Dmitry Vyukov wrote: > >>> Easier said than done. "normal user of the serial port" is not really > >>> a thing in Linux, right? You either have CAP_SYS_ADMIN or not, that's > >>> not per-device... > >>> As far as I remember +Tetsuo proposed a config along the lines of > >>> "restrict only things that legitimately cause damage under a fuzzer > >>> workload", e.g. freezing filesystems, disabling console output, etc. > >>> This may be another candidate. But I can't find where that proposal is > >>> now. > >> > >> That suggestion got no response for two months. > >> > >> https://lkml.kernel.org/r/3e4e2b6b-7828-54ab-cf28-db1a396d7e20@i-love.sakura.ne.jp > >> > >> Unless we add such kernel config option to upstream kernels, it will become > >> a whack-a-mole game. > > > > It will be a whack-a-mole game no matter what. > > > > Yes, /dev/mem/ makes no sense to fuzz. Neither does other things (like > > serial port memory addresses.) > > /dev/mem makes sense to fuzz. Ditto for other things. What? What are you going to find if you randomly start to write to /dev/mem? How are we supposed to "fix" that? > > You just will have a list of things that you "do not fuzz as these are > > dangerous". Nothing new here, any os will have that. > > The list of kernel config options will become too complicated to maintain. > If we can have one kernel config option, we can avoid maintaining > the list of kernel config options (which keeps changing over time). Use the newly added security_locked_down() call, that gives you a great indication that root can cause problems for those things. And it's not a config thing, it's a functionality thing within features, as is explicitly shown by this very thread for the serial port memory location. thanks, greg k-h