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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,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 EFFEDC48BD3 for ; Wed, 26 Jun 2019 16:21:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id BD7802084B for ; Wed, 26 Jun 2019 16:21:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726227AbfFZQVu (ORCPT ); Wed, 26 Jun 2019 12:21:50 -0400 Received: from fieldses.org ([173.255.197.46]:35062 "EHLO fieldses.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725958AbfFZQVt (ORCPT ); Wed, 26 Jun 2019 12:21:49 -0400 Received: by fieldses.org (Postfix, from userid 2815) id 597E3C56; Wed, 26 Jun 2019 12:21:49 -0400 (EDT) Date: Wed, 26 Jun 2019 12:21:49 -0400 From: "J. Bruce Fields" To: Kees Cook Cc: linux-nfs@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 08/16] nfsd: escape high characters in binary data Message-ID: <20190626162149.GB4144@fieldses.org> References: <1561042275-12723-1-git-send-email-bfields@redhat.com> <1561042275-12723-9-git-send-email-bfields@redhat.com> <20190621174544.GC25590@fieldses.org> <201906211431.E6552108@keescook> <20190622190058.GD5343@fieldses.org> <201906221320.5BFC134713@keescook> <20190624210512.GA20331@fieldses.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190624210512.GA20331@fieldses.org> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-nfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-nfs@vger.kernel.org On Mon, Jun 24, 2019 at 05:05:12PM -0400, J. Bruce Fields wrote: > On Sat, Jun 22, 2019 at 01:22:56PM -0700, Kees Cook wrote: > > On Sat, Jun 22, 2019 at 03:00:58PM -0400, J. Bruce Fields wrote: > > > The logic around ESCAPE_NP and the "only" string is really confusing. I > > > started assuming I could just add an ESCAPE_NONASCII flag and stick " > > > and \ into the "only" string, but it doesn't work that way. > > > > Yeah, if ESCAPE_NP isn't specified, the "only" characters are passed > > through. It'd be nice to have an "add" or a clearer way to do actual > > ctype subsets, etc. If there isn't an obviously clear way to refactor > > it, just skip it for now and I'm happy to ack your original patch. :) > > There may well be some simplification possible here.... There aren't > really many users of "only", for example. I'll look into it some more. The printk users are kind of mysterious to me. I did a grep for git grep '%[0-9.*]pE' which got 75 hits. All of them for pE. I couldn't find any of the other pE[achnops] variants. pE is equivalent to ESCAPE_ANY|ESCAPE_NP. Confusingly, ESCAPE_NP doesn't mean "escape non-printable", it means "don't escape printable". So things like carriage returns aren't escaped. Of those 57 were in drivers/net/wireless, and from a quick check seemed mostly to be for SSIDs in debug messages. I *think* SSIDs can be arbitrary bytes? If they really want them escaped then I suspect they want more than just nonprintable characters escaped. One of the hits outside wireless code was in drm_dp_cec_adap_status, which was printing some device ID into a debugfs file with "ID: %*pE\n". If the ID actually needs escaping, then I suspect the meant to escape \n too to prevent misparsing that output. --b.