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=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 3DF39C04A6B for ; Mon, 6 May 2019 15:24:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 19299205ED for ; Mon, 6 May 2019 15:24:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726896AbfEFPYv (ORCPT ); Mon, 6 May 2019 11:24:51 -0400 Received: from smtp1.de.adit-jv.com ([93.241.18.167]:56963 "EHLO smtp1.de.adit-jv.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726484AbfEFPYs (ORCPT ); Mon, 6 May 2019 11:24:48 -0400 Received: from localhost (smtp1.de.adit-jv.com [127.0.0.1]) by smtp1.de.adit-jv.com (Postfix) with ESMTP id E8B6F3C00C6; Mon, 6 May 2019 17:24:43 +0200 (CEST) Received: from smtp1.de.adit-jv.com ([127.0.0.1]) by localhost (smtp1.de.adit-jv.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id t12YR46iAR7u; Mon, 6 May 2019 17:24:37 +0200 (CEST) Received: from HI2EXCH01.adit-jv.com (hi2exch01.adit-jv.com [10.72.92.24]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-SHA384 (256/256 bits)) (No client certificate requested) by smtp1.de.adit-jv.com (Postfix) with ESMTPS id C2C1B3C004C; Mon, 6 May 2019 17:24:36 +0200 (CEST) Received: from vmlxhi-102.adit-jv.com (10.72.93.184) by HI2EXCH01.adit-jv.com (10.72.92.24) with Microsoft SMTP Server (TLS) id 14.3.439.0; Mon, 6 May 2019 17:24:36 +0200 Date: Mon, 6 May 2019 17:24:33 +0200 From: Eugeniu Rosca To: Simon Horman CC: Eugeniu Rosca , Geert Uytterhoeven , Chris Brandt , Wolfram Sang , Ulrich Hecht , Greg Kroah-Hartman , "George G . Davis" , Andy Lowe , , , , Magnus Damm , Rob Herring , Mark Rutland , Christophe Leroy , Helge Deller , Michael Neuling , Kuninori Morimoto , Philip Yang , Matthew Wilcox , Borislav Petkov , "Darrick J. Wong" , Eugeniu Rosca Subject: Re: [PATCH 1/6] serial: sh-sci: Reveal ptrval in dev_dbg Message-ID: <20190506152433.GA22769@vmlxhi-102.adit-jv.com> References: <20190504004258.23574-1-erosca@de.adit-jv.com> <20190504004258.23574-2-erosca@de.adit-jv.com> <20190506134700.ya565idfzzc3enbm@verge.net.au> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <20190506134700.ya565idfzzc3enbm@verge.net.au> User-Agent: Mutt/1.5.24 (2015-08-30) X-Originating-IP: [10.72.93.184] Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, May 06, 2019 at 03:47:05PM +0200, Simon Horman wrote: > On Sat, May 04, 2019 at 02:42:53AM +0200, Eugeniu Rosca wrote: > > Starting with v4.15-rc2 commit ad67b74d2469d9 ("printk: hash addresses > > printed with %p"), enabling debug prints in sh-sci.c would generate > > output like below confusing the users who try to sneak into the > > internals of the driver: > > > > sh-sci e6e88000.serial: sci_request_dma: TX: got channel (____ptrval____) > > sh-sci e6e88000.serial: sci_request_dma: mapped 4096@(____ptrval____) to 0x00000006798bf000 > > sh-sci e6e88000.serial: sci_request_dma: RX: got channel (____ptrval____) > > sh-sci e6e88000.serial: sci_dma_tx_work_fn: (____ptrval____): 0...2, cookie 2 > > > > There are two possible fixes for that: > > - get rid of '%p' prints if they don't reveal any useful information > > - s/%p/%px/, since it is unlikely we have any concerns leaking the > > pointer values when running a debug/non-production kernel > > I am concerned that this may expose information in circumstances > where it is undesirable. Is it generally accepted practice to > use %px in conjunction with dev_dbg() ? > > ... Below commits performed a similar s/%p/%px/ update in debug context: Authors (CC-ed) Commit Subject ---------------------------------------- Christophe Leroy b18f0ae92b0a1d ("powerpc/prom: fix early DEBUG messages") Helge Deller 3847dab7742186 ("parisc: Add alternative coding infrastructure") Michael Neuling 51c3c62b58b357 ("powerpc: Avoid code patching freed init sections") Kuninori Morimoto dabdbe3ae0cb9a ("ASoC: rsnd: don't use %p for dev_dbg()") Philip Yang fa7e65147e5dca ("drm/amdkfd: use %px to print user space address instead of %p") Matthew Wilcox 68c1f08203f2b0 ("lib/list_debug.c: print unmangled addresses") Borislav Petkov 0e6c16c652cada ("x86/alternative: Print unadorned pointers") Darrick J. Wong c96900435fa9fd ("xfs: use %px for data pointers when debugging") Helge Deller 04903c06b4854d ("parisc: Show unhashed HPA of Dino chip") To quote Matthew, with respect to any debug prints: If an attacker can force this message to be printed, we've already lost. In any case, I won't be affected much if the change is not accepted, since it doesn't resolve any major issue on my end. Thanks! -- Best Regards, Eugeniu.