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=-8.4 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 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 63C7BC433FF for ; Mon, 12 Aug 2019 16:48:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1CE4B2070C for ; Mon, 12 Aug 2019 16:48:35 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=ti.com header.i=@ti.com header.b="EtBAz1CB" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726937AbfHLQse (ORCPT ); Mon, 12 Aug 2019 12:48:34 -0400 Received: from fllv0016.ext.ti.com ([198.47.19.142]:56810 "EHLO fllv0016.ext.ti.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725843AbfHLQsd (ORCPT ); Mon, 12 Aug 2019 12:48:33 -0400 Received: from fllv0035.itg.ti.com ([10.64.41.0]) by fllv0016.ext.ti.com (8.15.2/8.15.2) with ESMTP id x7CGmPFa126458; Mon, 12 Aug 2019 11:48:25 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ti.com; s=ti-com-17Q1; t=1565628505; bh=K2kWznbWIdZ/ricVAmUmB19KtEM09fU55kzjXYmQvME=; h=Subject:To:CC:References:From:Date:In-Reply-To; b=EtBAz1CBkH6KcNuHZ+Xzm2pfaPkKbZD01UtweuaQzS5/iMmyGZ3UADy2KWVd9o/HU HdfJuEV/QBDS7wWe3EFjlqJ5dpmbrFARrTynOdIS2Knqb5eNkdxR4GLd5/M8y+Ru0l APAEACMfboFZtCAGY99C7YtiMJo+DWXjnVMBuYeg= Received: from DLEE108.ent.ti.com (dlee108.ent.ti.com [157.170.170.38]) by fllv0035.itg.ti.com (8.15.2/8.15.2) with ESMTPS id x7CGmP2G090732 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=FAIL); Mon, 12 Aug 2019 11:48:25 -0500 Received: from DLEE115.ent.ti.com (157.170.170.26) by DLEE108.ent.ti.com (157.170.170.38) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.1713.5; Mon, 12 Aug 2019 11:48:25 -0500 Received: from fllv0040.itg.ti.com (10.64.41.20) by DLEE115.ent.ti.com (157.170.170.26) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.1713.5 via Frontend Transport; Mon, 12 Aug 2019 11:48:25 -0500 Received: from [10.250.88.190] (ileax41-snat.itg.ti.com [10.172.224.153]) by fllv0040.itg.ti.com (8.15.2/8.15.2) with ESMTP id x7CGmOjZ130439; Mon, 12 Aug 2019 11:48:24 -0500 Subject: Re: [PATCH] rpmsg: virtio_rpmsg_bus: replace "%p" with "%pK" To: Suman Anna , Bjorn Andersson CC: , Loic Pallardy , , References: <20181024011909.21674-1-s-anna@ti.com> <1cc3d697-6fde-901b-2e35-2e2b53b44425@ti.com> <2ef5e274-df09-c3a0-41ed-a945d1902eaf@ti.com> <92dc4403-8782-8dbf-b912-cc832ac748a7@ti.com> From: "Andrew F. Davis" Message-ID: <292d913f-7f4e-52ee-13bc-36014acee646@ti.com> Date: Mon, 12 Aug 2019 12:48:24 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit X-EXCLAIMER-MD-CONFIG: e1e8a2fd-e40a-4ac6-ac9b-f7e9cc9ee180 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 8/12/19 12:39 PM, Suman Anna wrote: > On 8/12/19 11:36 AM, Andrew F. Davis wrote: >> On 8/12/19 12:28 PM, Suman Anna wrote: >>> On 8/12/19 10:47 AM, Andrew F. Davis wrote: >>>> On 10/23/18 9:19 PM, Suman Anna wrote: >>>>> The virtio_rpmsg_bus driver uses the "%p" format-specifier for >>>>> printing the vring buffer address. This prints only a hashed >>>>> pointer even for previliged users. Use "%pK" instead so that >>>>> the address can be printed during debug using kptr_restrict >>>>> sysctl. >>>>> >>>> >>>> >>>> s/previliged/privileged >>> >>> Bjorn, >>> Can you fix this up when applying. >>> >>>> >>>> You describe what the code does, but not why you need this. %pK is used >>>> for only about 1% of pointer printing, why do you want to leak this >>>> address to userspace at all? >>> >>> Andrew, >>> Default behavior of %pK is same as %p, but it does allow you to control >>> the print. The reason is clearly mentioned in the last sentence in the >>> patch description. >>> >> >> >> Let me rephrase then, why would you ever set 'kptr_restrict' to anything >> other than 0, or why do you want to be able to leak this address to >> userspace at all? If the answer is just because you can, then all 12,000 >> instances of %p in kernel could be converted for the same reason. > > It is a dev_dbg statement, so it is already under dynamic debug control. > We would only ever use it during debug. > Most pointer printings are in debug statements.. I'm simply not seeing what this helps us do. The DMA address I can understand, it may be given to a remote core so we may want to verify it is the same on both sides, but the actual virtual kernel address is of no value to us, a hash to track it across uses is just as good. Andrew > regards > Suman > >> >> Andrew >> >> >>> regards >>> Suman >>> >>>> >>>> Andrew >>>> >>>> >>>>> Signed-off-by: Suman Anna >>>>> --- >>>>> drivers/rpmsg/virtio_rpmsg_bus.c | 2 +- >>>>> 1 file changed, 1 insertion(+), 1 deletion(-) >>>>> >>>>> diff --git a/drivers/rpmsg/virtio_rpmsg_bus.c b/drivers/rpmsg/virtio_rpmsg_bus.c >>>>> index f29dee731026..1345f373a1a0 100644 >>>>> --- a/drivers/rpmsg/virtio_rpmsg_bus.c >>>>> +++ b/drivers/rpmsg/virtio_rpmsg_bus.c >>>>> @@ -950,7 +950,7 @@ static int rpmsg_probe(struct virtio_device *vdev) >>>>> goto vqs_del; >>>>> } >>>>> >>>>> - dev_dbg(&vdev->dev, "buffers: va %p, dma %pad\n", >>>>> + dev_dbg(&vdev->dev, "buffers: va %pK, dma %pad\n", >>>>> bufs_va, &vrp->bufs_dma); >>>>> >>>>> /* half of the buffers is dedicated for RX */ >>>>> >>> >