From patchwork Sun Sep 1 14:07:30 2013 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: David Herrmann X-Patchwork-Id: 2852566 Return-Path: X-Original-To: patchwork-linux-input@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork2.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.19.201]) by patchwork2.web.kernel.org (Postfix) with ESMTP id A24C9C0AB5 for ; Sun, 1 Sep 2013 14:07:50 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 8FE2F20303 for ; Sun, 1 Sep 2013 14:07:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 49917202F8 for ; Sun, 1 Sep 2013 14:07:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753273Ab3IAOHr (ORCPT ); Sun, 1 Sep 2013 10:07:47 -0400 Received: from mail-ea0-f174.google.com ([209.85.215.174]:65322 "EHLO mail-ea0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752532Ab3IAOHq (ORCPT ); Sun, 1 Sep 2013 10:07:46 -0400 Received: by mail-ea0-f174.google.com with SMTP id z15so1822458ead.5 for ; Sun, 01 Sep 2013 07:07:45 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=from:to:cc:subject:date:message-id:in-reply-to:references; bh=Ya1P54zknQC4jUA03QWKyMtltTONeOWPP5j8zL7GaUc=; b=GKRSpkBdNDjfoUKtDJSqQoWiu548WYV5dEr1vyHV4zhWKW12QGWH0MlVxqfWnFaaHi L/ta0vCOhXr3sCB/e3XfLVKu9tAYj2ndD0PG6T1RZ0ch00Zd9LxcUeMhGLnLjZm7mACt NhigtRG4eIlSzY0frnvAAPiZ/2Nrz7m9yqBnzE3jaURhLTEGIR677dK/geT5t+UbDm32 hpV4sTezr3Jh7rZ6GExoVgj0HGoVg8ys75qVDA12YouRyJM6rKYO7ATG3XVn2rqkujUy clitBoLoQclhXX8tkE7qkZzczZY3mqtCR3CN2/T1857slHG4ePG2zaF+EvWKvAKQSZf4 wkaQ== X-Received: by 10.15.83.2 with SMTP id b2mr29199960eez.28.1378044465289; Sun, 01 Sep 2013 07:07:45 -0700 (PDT) Received: from localhost.localdomain (stgt-5f719c52.pool.mediaWays.net. [95.113.156.82]) by mx.google.com with ESMTPSA id p5sm13632205eeg.5.1969.12.31.16.00.00 (version=TLSv1.2 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Sun, 01 Sep 2013 07:07:44 -0700 (PDT) From: David Herrmann To: linux-input@vger.kernel.org Cc: Dmitry Torokhov , David Herrmann Subject: [PATCH v3] Input: evdev - add EVIOCREVOKE ioctl Date: Sun, 1 Sep 2013 16:07:30 +0200 Message-Id: <1378044450-8327-1-git-send-email-dh.herrmann@gmail.com> X-Mailer: git-send-email 1.8.4 In-Reply-To: <1377603589-25501-1-git-send-email-dh.herrmann@gmail.com> References: <1377603589-25501-1-git-send-email-dh.herrmann@gmail.com> Sender: linux-input-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-input@vger.kernel.org X-Spam-Status: No, score=-9.2 required=5.0 tests=BAYES_00, DKIM_ADSP_CUSTOM_MED, DKIM_SIGNED, FREEMAIL_FROM, RCVD_IN_DNSWL_HI, RP_MATCHES_RCVD, T_DKIM_INVALID, UNPARSEABLE_RELAY autolearn=ham version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP If we have multiple sessions on a system, we normally don't want background sessions to read input events. Otherwise, it could capture passwords and more entered by the user on the foreground session. This is a real world problem as the recent XMir development showed: http://mjg59.dreamwidth.org/27327.html We currently rely on sessions to release input devices when being deactivated. This relies on trust across sessions. But that's not given on usual systems. We therefore need a way to control which processes have access to input devices. With VTs the kernel simply routed them through the active /dev/ttyX. This is not possible with evdev devices, though. Moreover, we want to avoid routing input-devices through some dispatcher-daemon in userspace (which would add some latency). This patch introduces EVIOCREVOKE. If called on an evdev fd, this revokes device-access irrecoverably for that *single* open-file. Hence, once you call EVIOCREVOKE on any dup()ed fd, all fds for that open-file will be rather useless now (but still valid compared to close()!). This allows us to pass fds directly to session-processes from a trusted source. The source keeps a dup()ed fd and revokes access once the session-process is no longer active. Compared to the EVIOCMUTE proposal, we can avoid the CAP_SYS_ADMIN restriction now as there is no way to revive the fd again. Hence, a user is free to call EVIOCREVOKE themself to kill the fd. Additionally, this ioctl allows multi-layer access-control (again compared to EVIOCMUTE which was limited to one layer via CAP_SYS_ADMIN). A middle layer can simply request a new open-file from the layer above and pass it to the layer below. Now each layer can call EVIOCREVOKE on the fds to revoke access for all layers below, at the expense of one fd per layer. There's already ongoing experimental user-space work which demonstrates how it can be used: http://lists.freedesktop.org/archives/systemd-devel/2013-August/012897.html Signed-off-by: David Herrmann Reviewed-by: Kristian Høgsberg --- Changes from v2: - Handle client->revoked like evdev->exist to avoid special-casing "revoked" drivers/input/evdev.c | 33 +++++++++++++++++++++++++++++---- include/uapi/linux/input.h | 1 + 2 files changed, 30 insertions(+), 4 deletions(-) diff --git a/drivers/input/evdev.c b/drivers/input/evdev.c index d2b34fb..cf6bdff 100644 --- a/drivers/input/evdev.c +++ b/drivers/input/evdev.c @@ -48,6 +48,7 @@ struct evdev_client { struct evdev *evdev; struct list_head node; int clkid; + bool revoked; unsigned int bufsize; struct input_event buffer[]; }; @@ -164,6 +165,9 @@ static void evdev_pass_values(struct evdev_client *client, struct input_event event; bool wakeup = false; + if (client->revoked) + return; + event.time = ktime_to_timeval(client->clkid == CLOCK_MONOTONIC ? mono : real); @@ -429,7 +433,7 @@ static ssize_t evdev_write(struct file *file, const char __user *buffer, if (retval) return retval; - if (!evdev->exist) { + if (!evdev->exist || client->revoked) { retval = -ENODEV; goto out; } @@ -511,7 +515,7 @@ static ssize_t evdev_read(struct file *file, char __user *buffer, if (!(file->f_flags & O_NONBLOCK)) { error = wait_event_interruptible(evdev->wait, client->packet_head != client->tail || - !evdev->exist); + !evdev->exist || client->revoked); if (error) return error; } @@ -529,7 +533,11 @@ static unsigned int evdev_poll(struct file *file, poll_table *wait) poll_wait(file, &evdev->wait, wait); - mask = evdev->exist ? POLLOUT | POLLWRNORM : POLLHUP | POLLERR; + if (evdev->exist && !client->revoked) + mask = POLLOUT | POLLWRNORM; + else + mask = POLLHUP | POLLERR; + if (client->packet_head != client->tail) mask |= POLLIN | POLLRDNORM; @@ -795,6 +803,17 @@ static int evdev_handle_mt_request(struct input_dev *dev, return 0; } +static int evdev_revoke(struct evdev *evdev, struct evdev_client *client, + struct file *file) +{ + client->revoked = true; + evdev_ungrab(evdev, client); + input_flush_device(&evdev->handle, file); + wake_up_interruptible(&evdev->wait); + + return 0; +} + static long evdev_do_ioctl(struct file *file, unsigned int cmd, void __user *p, int compat_mode) { @@ -857,6 +876,12 @@ static long evdev_do_ioctl(struct file *file, unsigned int cmd, else return evdev_ungrab(evdev, client); + case EVIOCREVOKE: + if (p) + return -EINVAL; + else + return evdev_revoke(evdev, client, file); + case EVIOCSCLOCKID: if (copy_from_user(&i, p, sizeof(unsigned int))) return -EFAULT; @@ -1002,7 +1027,7 @@ static long evdev_ioctl_handler(struct file *file, unsigned int cmd, if (retval) return retval; - if (!evdev->exist) { + if (!evdev->exist || client->revoked) { retval = -ENODEV; goto out; } diff --git a/include/uapi/linux/input.h b/include/uapi/linux/input.h index 2fb6fae..d61c61c 100644 --- a/include/uapi/linux/input.h +++ b/include/uapi/linux/input.h @@ -152,6 +152,7 @@ struct input_keymap_entry { #define EVIOCGEFFECTS _IOR('E', 0x84, int) /* Report number of effects playable at the same time */ #define EVIOCGRAB _IOW('E', 0x90, int) /* Grab/Release device */ +#define EVIOCREVOKE _IOW('E', 0x91, int) /* Revoke device access */ #define EVIOCSCLOCKID _IOW('E', 0xa0, int) /* Set clockid to be used for timestamps */