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=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS 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 C3B3EC43381 for ; Wed, 20 Mar 2019 17:51:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9AD652184D for ; Wed, 20 Mar 2019 17:51:08 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="key not found in DNS" (0-bit key) header.d=codeaurora.org header.i=@codeaurora.org header.b="FntXEGzf"; dkim=fail reason="key not found in DNS" (0-bit key) header.d=codeaurora.org header.i=@codeaurora.org header.b="W4qbIMwC" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727405AbfCTRvH (ORCPT ); Wed, 20 Mar 2019 13:51:07 -0400 Received: from smtp.codeaurora.org ([198.145.29.96]:51808 "EHLO smtp.codeaurora.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726049AbfCTRvH (ORCPT ); Wed, 20 Mar 2019 13:51:07 -0400 Received: by smtp.codeaurora.org (Postfix, from userid 1000) id 760DD613A6; Wed, 20 Mar 2019 17:51:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=codeaurora.org; s=default; t=1553104265; bh=PHNM6bheDeYTYw6yVXCWWJXVJOBrCq9mHZwunwKQbB8=; h=Subject:To:Cc:References:From:Date:In-Reply-To:From; b=FntXEGzfrCDnynFGONDw/bdW5vp+yjNhDC+zJoHwRZ+P0Q5740JwQw3p1npKANMpM vzFgBY07+MpfGgXba2jGzbJusvQDCxEPByCHCe6vXhI+2SA+8vxS2rvgsrbqoqpOQE OaQ+G5ShYxBFOxZ2DxVGNmc1ofbRYwqhjNIuBFn8= Received: from [192.168.1.4] (unknown [122.175.119.127]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) (Authenticated sender: gkohli@smtp.codeaurora.org) by smtp.codeaurora.org (Postfix) with ESMTPSA id 745C960EA5; Wed, 20 Mar 2019 17:51:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=codeaurora.org; s=default; t=1553104264; bh=PHNM6bheDeYTYw6yVXCWWJXVJOBrCq9mHZwunwKQbB8=; h=Subject:To:Cc:References:From:Date:In-Reply-To:From; b=W4qbIMwCsq0L/NojacFvSLpU0cHR0NW2FGW2/gNqQpF7+xOCOP/h9Ijdi7j5cgBCl zk/e/HUa/7qENGW/p/mg6aD7KN8/yZDdVfgEA9n0pLUDBJIGPWUY5X8Y8tLkDaJEi5 bZ/cvOq+ojvlNH+yBbwCOb8ghOb6+ewB+6FA6Waw= DMARC-Filter: OpenDMARC Filter v1.3.2 smtp.codeaurora.org 745C960EA5 Authentication-Results: pdx-caf-mail.web.codeaurora.org; dmarc=none (p=none dis=none) header.from=codeaurora.org Authentication-Results: pdx-caf-mail.web.codeaurora.org; spf=none smtp.mailfrom=gkohli@codeaurora.org Subject: Re: [PATCH v2] nvmem: core: Set no-read-write provider to avoid userspace read/write To: Srinivas Kandagatla , linux-kernel@vger.kernel.org Cc: linux-arm-msm@vger.kernel.org References: <1552831940-7327-1-git-send-email-gkohli@codeaurora.org> <48a71861-c60b-7fe7-d4af-5269cd7c20eb@linaro.org> <5f11070f-bf9b-c313-9a78-e412a2fb2908@codeaurora.org> <865519b5-62c9-3eb3-3855-eebf98bded85@linaro.org> From: Gaurav Kohli Message-ID: <68755fdb-b2c6-ac25-a786-7593a692a173@codeaurora.org> Date: Wed, 20 Mar 2019 23:20:59 +0530 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.5.3 MIME-Version: 1.0 In-Reply-To: <865519b5-62c9-3eb3-3855-eebf98bded85@linaro.org> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 3/20/2019 9:56 PM, Srinivas Kandagatla wrote: > > > On 20/03/2019 15:50, Gaurav Kohli wrote: >> >> On 3/20/2019 8:04 PM, Srinivas Kandagatla wrote: >>> >>> >>> On 17/03/2019 14:12, Gaurav Kohli wrote: >>>> Current nvmem framework allows user space to read all register space >>>> populated by nvmem binary file, In case we don't want to expose value >>>> of registers to userspace and only want kernel space to read cell >>>> value from nvmem_cell_read_u32. >>>> >>>> To protect the same, Add no-read-write property to prevent read >>>> from userspace. >>>> >>> >>> Can you explain the real need of this? >>> Is there any issue you are noticing while reading nvmem content from >>> userspace? >>> >> Hi Srinivas, >> >> >> No, We are not observing any issue, nvmem is dumping the data properly. >> >> But there are certain register, which we don't want to expose to user >> space and want kernel space can only read via nvmem_cell_read. > Am guessing these are some kind of keys or something that you do not > want user to see. > Hi Srinivas, Thanks. Yes exactly, there are certain keys or even certain bit that we don't want to expose to user. > Is root only option not helping you in this case? Yes we want to protect at root level as well, i mean it is better if we can avoid exposing to userspace at all. > > We could go down the route of adding new config option something like > CONFIG_NVMEM_NO_SYSFS_ENTRY to prevent adding nvmem entry in userspace. > > Let me know if you are happy to create a patch for this change? I am happy with either way config option or dt binding(seems easy), please let me know we will post new patch for the same. In config option, do i have to remove all binary creation code of nvmem , correct? or simply put a check like dt binding option so user cannot read it. Thanks Gaurav > > Thanks, > srini > >> >> In existing design, even if we read cell from kernel space, nvmem >> binary files is still populated to user space unconditionally. >> >> Regards >> >> Gaurav -- Qualcomm India Private Limited, on behalf of Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project.