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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id B097BC433F5 for ; Fri, 28 Jan 2022 09:36:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S243621AbiA1JgI (ORCPT ); Fri, 28 Jan 2022 04:36:08 -0500 Received: from ams.source.kernel.org ([145.40.68.75]:52044 "EHLO ams.source.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238119AbiA1JgH (ORCPT ); Fri, 28 Jan 2022 04:36:07 -0500 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id D69E4B818E0 for ; Fri, 28 Jan 2022 09:36:05 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3B31EC340E0; Fri, 28 Jan 2022 09:36:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1643362564; bh=RNYx0y7rlPXfR94RfuO4OdTpV0HZfT1xQgB4lqpedt8=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=uxuN3efWq5y8qyUWiS+rk/tbXIS+awH4jtFT0DGXBhj3ymKei0v7fcIwhG34XlBbH lWp0+9LZY2GBao+Sq+vSU7Ohq18OsAgwxm4AptD5ip+tmMpGo8ESdbE3qsLsQFc82d vKvkPgejcXCdAUJ7k1RNE0vzX1h90YfxSY2LmtEM= Date: Fri, 28 Jan 2022 10:36:01 +0100 From: Greg KH To: Sami Kyostila Cc: LKML , dtor@chromium.org, evanbenn@chromium.org, arnd@arndb.de Subject: Re: [PATCH 2/2] drivers/misc: add transfer ioctl for HPS Message-ID: References: <20220127083545.1020423-1-skyostil@chromium.org> <20220127083545.1020423-3-skyostil@chromium.org> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jan 28, 2022 at 06:42:08PM +1100, Sami Kyostila wrote: > to 27. tammik. 2022 klo 20.41 Greg KH (gregkh@linuxfoundation.org) kirjoitti: > > > > On Thu, Jan 27, 2022 at 07:35:45PM +1100, Sami Kyöstilä wrote: > > > This patch adds an ioctl operation for sending and receiving data from > > > the ChromeOS snooping protection sensor (a.k.a., HPS). This allows > > > userspace programs to perform a combined read/write I2C transaction > > > through a single syscall. > > > > > > The I2C wire protocol for the device is documented at: > > > > > > https://chromium.googlesource.com/chromiumos/platform/hps-firmware/+/ > > > refs/heads/main/docs/host_device_i2c_protocol.md > > > > > > Signed-off-by: Sami Kyöstilä > > > --- > > > > > > MAINTAINERS | 1 + > > > drivers/misc/hps-i2c.c | 81 ++++++++++++++++++++++++++++++++++++++++ > > > include/uapi/linux/hps.h | 20 ++++++++++ > > > 3 files changed, 102 insertions(+) > > > create mode 100644 include/uapi/linux/hps.h > > > > > > diff --git a/MAINTAINERS b/MAINTAINERS > > > index 9dea4b8c2ab5..d5fc066fdbc2 100644 > > > --- a/MAINTAINERS > > > +++ b/MAINTAINERS > > > @@ -8803,6 +8803,7 @@ M: Sami Kyöstilä > > > R: Evan Benn > > > S: Maintained > > > F: drivers/misc/hps-i2c.c > > > +F: include/uapi/linux/hps.h > > > > > > HSI SUBSYSTEM > > > M: Sebastian Reichel > > > diff --git a/drivers/misc/hps-i2c.c b/drivers/misc/hps-i2c.c > > > index fe9f073b0352..748ead49d678 100644 > > > --- a/drivers/misc/hps-i2c.c > > > +++ b/drivers/misc/hps-i2c.c > > > @@ -17,9 +17,11 @@ > > > #include > > > #include > > > #include > > > +#include > > > > > > #define HPS_ACPI_ID "GOOG0020" > > > #define HPS_MAX_DEVICES 1 > > > +#define HPS_MAX_MSG_SIZE 8192 > > > > > > struct hps_drvdata { > > > struct i2c_client *client; > > > @@ -60,6 +62,8 @@ static int hps_open(struct inode *inode, struct file *file) > > > ret = pm_runtime_get_sync(dev); > > > if (ret < 0) > > > goto pm_get_fail; > > > + > > > + file->private_data = hps->client; > > > return 0; > > > > > > pm_get_fail: > > > @@ -84,10 +88,87 @@ static int hps_release(struct inode *inode, struct file *file) > > > return ret; > > > } > > > > > > +static int hps_do_ioctl_transfer(struct i2c_client *client, > > > + struct hps_transfer_ioctl_data *args) > > > +{ > > > + int ret; > > > + int nmsg = 0; > > > + struct i2c_msg msgs[2] = { > > > + { > > > + .addr = client->addr, > > > + .flags = client->flags, > > > + }, > > > + { > > > + .addr = client->addr, > > > + .flags = client->flags, > > > + }, > > > + }; > > > + > > > + if (args->isize) { > > > + msgs[nmsg].len = args->isize; > > > + msgs[nmsg].buf = memdup_user(args->ibuf, args->isize); > > > + if (IS_ERR(msgs[nmsg].buf)) { > > > + ret = PTR_ERR(msgs[nmsg].buf); > > > + goto memdup_fail; > > > + } > > > + nmsg++; > > > + } > > > + > > > + if (args->osize) { > > > + msgs[nmsg].len = args->osize; > > > + msgs[nmsg].buf = memdup_user(args->obuf, args->osize); > > > + msgs[nmsg].flags |= I2C_M_RD; > > > + if (IS_ERR(msgs[nmsg].buf)) { > > > + ret = PTR_ERR(msgs[nmsg].buf); > > > + goto memdup_fail; > > > + } > > > + nmsg++; > > > + } > > > + > > > + ret = i2c_transfer(client->adapter, &msgs[0], nmsg); > > > + if (ret > 0 && args->osize) { > > > + if (copy_to_user(args->obuf, msgs[nmsg - 1].buf, ret)) > > > + ret = -EFAULT; > > > + } > > > > Why can't you just do normal i2c transfers to/from userspace instead of > > requring a custom ioctl? > > The main reason is security: without this driver, in order to talk to > HPS the userspace daemon needs read/write access to the entire I2C > controller (e.g., /dev/i2c-0). This means the daemon can also control > any other I2C device which happens to be on the same bus. With a > separate ioctl we can limit access to just HPS. Then use seccomp for this? > As far as I can tell, there's no way to restrict access on a > per-device level with normal i2c, but I'd be happy to be proven wrong > :) Selinux rules? What else is on this bus for the device that you care about? thanks, greg k-h