diff mbox series

[v3] HID: hidraw - add HIDIOCREVOKE ioctl

Message ID 20240812052753.GA478917@quokka (mailing list archive)
State New
Headers show
Series [v3] HID: hidraw - add HIDIOCREVOKE ioctl | expand

Commit Message

Peter Hutterer Aug. 12, 2024, 5:27 a.m. UTC
There is a need for userspace applications to open HID devices directly.
Use-cases include configuration of gaming mice or direct access to
joystick devices. The latter is currently handled by the uaccess tag in
systemd, other devices include more custom/local configurations or just
sudo.

A better approach is what we already have for evdev devices: give the
application a file descriptor and revoke it when it may no longer access
that device.

This patch is the hidraw equivalent to the EVIOCREVOKE ioctl, see
commit c7dc65737c9a607d3e6f8478659876074ad129b8 for full details.

An MR for systemd-logind has been filed here:
https://github.com/systemd/systemd/pull/33970

hidraw_is_revoked() and hidraw_open_errno() are both defined as weak
functions to allow for a BPF program to deny access to a /dev/hidraw
device. The function returns 0 on success or a negative errno
otherwise that is returned to the caller.

As a use-case example, a gamepad-managing process could attach a BPF
program that defaults to -EACCESS for all hidraw devices except those
with ID_INPUT_JOYSTICK set by udev.

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
---
First version of the patch:
https://patchwork.kernel.org/project/linux-input/patch/YmEAPZKDisM2HAsG@quokka/

Changes to v1:
- add the hidraw_is_revoked and hidraw_open_errno weak functions as
  suggested by Benjamin

Changes to v2:
- use __bpf_hook_start/end to silence compiler warnings  (see kernel
  test bot)

 drivers/hid/hidraw.c        | 61 ++++++++++++++++++++++++++++++++++---
 include/linux/hidraw.h      |  1 +
 include/uapi/linux/hidraw.h |  1 +
 3 files changed, 58 insertions(+), 5 deletions(-)

Comments

Jiri Kosina Aug. 21, 2024, 12:31 a.m. UTC | #1
On Mon, 12 Aug 2024, Peter Hutterer wrote:

> There is a need for userspace applications to open HID devices directly.
> Use-cases include configuration of gaming mice or direct access to
> joystick devices. The latter is currently handled by the uaccess tag in
> systemd, other devices include more custom/local configurations or just
> sudo.
> 
> A better approach is what we already have for evdev devices: give the
> application a file descriptor and revoke it when it may no longer access
> that device.
> 
> This patch is the hidraw equivalent to the EVIOCREVOKE ioctl, see
> commit c7dc65737c9a607d3e6f8478659876074ad129b8 for full details.
> 
> An MR for systemd-logind has been filed here:
> https://github.com/systemd/systemd/pull/33970
> 
> hidraw_is_revoked() and hidraw_open_errno() are both defined as weak
> functions to allow for a BPF program to deny access to a /dev/hidraw
> device. The function returns 0 on success or a negative errno
> otherwise that is returned to the caller.
> 
> As a use-case example, a gamepad-managing process could attach a BPF
> program that defaults to -EACCESS for all hidraw devices except those
> with ID_INPUT_JOYSTICK set by udev.
> 
> Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>

Thanks Peter. Now queued in hid.git#for-6.12/hidraw.
Peter Hutterer Aug. 21, 2024, 6:59 a.m. UTC | #2
Hi Jiri,

On Wed, Aug 21, 2024 at 02:31:32AM +0200, Jiri Kosina wrote:
> On Mon, 12 Aug 2024, Peter Hutterer wrote:
> 
> > There is a need for userspace applications to open HID devices directly.
> > Use-cases include configuration of gaming mice or direct access to
> > joystick devices. The latter is currently handled by the uaccess tag in
> > systemd, other devices include more custom/local configurations or just
> > sudo.
> > 
> > A better approach is what we already have for evdev devices: give the
> > application a file descriptor and revoke it when it may no longer access
> > that device.
> > 
> > This patch is the hidraw equivalent to the EVIOCREVOKE ioctl, see
> > commit c7dc65737c9a607d3e6f8478659876074ad129b8 for full details.
> > 
> > An MR for systemd-logind has been filed here:
> > https://github.com/systemd/systemd/pull/33970
> > 
> > hidraw_is_revoked() and hidraw_open_errno() are both defined as weak
> > functions to allow for a BPF program to deny access to a /dev/hidraw
> > device. The function returns 0 on success or a negative errno
> > otherwise that is returned to the caller.
> > 
> > As a use-case example, a gamepad-managing process could attach a BPF
> > program that defaults to -EACCESS for all hidraw devices except those
> > with ID_INPUT_JOYSTICK set by udev.
> > 
> > Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
> 
> Thanks Peter. Now queued in hid.git#for-6.12/hidraw.

Benjamin just messaged me about a HID CI pipeline failure caused by this
patch, looks like it's buggy. Can you please revert it again?  I'll send
out a fixed version ASAP, thanks.

Cheeres,
  Peter
Jiri Kosina Aug. 21, 2024, 12:58 p.m. UTC | #3
On Wed, 21 Aug 2024, Peter Hutterer wrote:

> Benjamin just messaged me about a HID CI pipeline failure caused by this
> patch, looks like it's buggy. Can you please revert it again?  I'll send
> out a fixed version ASAP, thanks.

OK, thanks for the report. It's now reverted in for-next, and branch 
for-6.12/hidraw is dropped.
diff mbox series

Patch

diff --git ./drivers/hid/hidraw.c ../drivers/hid/hidraw.c
index 2bc762d31ac7..baee5417e6e2 100644
--- ./drivers/hid/hidraw.c
+++ ../drivers/hid/hidraw.c
@@ -13,6 +13,7 @@ 
 
 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
 
+#include <linux/btf.h>
 #include <linux/fs.h>
 #include <linux/module.h>
 #include <linux/errno.h>
@@ -38,12 +39,35 @@  static const struct class hidraw_class = {
 static struct hidraw *hidraw_table[HIDRAW_MAX_DEVICES];
 static DECLARE_RWSEM(minors_rwsem);
 
+__bpf_hook_start();
+
+__weak noinline bool hidraw_is_revoked(struct hidraw_list *list)
+{
+	return list->revoked;
+}
+ALLOW_ERROR_INJECTION(hidraw_is_revoked, TRUE);
+
+__bpf_hook_end();
+
+__bpf_hook_start();
+
+__weak noinline int hidraw_open_errno(__u32 major, __u32 minor)
+{
+	return 0;
+}
+ALLOW_ERROR_INJECTION(hidraw_open_errno, ERRNO);
+
+__bpf_hook_end();
+
 static ssize_t hidraw_read(struct file *file, char __user *buffer, size_t count, loff_t *ppos)
 {
 	struct hidraw_list *list = file->private_data;
 	int ret = 0, len;
 	DECLARE_WAITQUEUE(wait, current);
 
+	if (hidraw_is_revoked(list))
+		return -ENODEV;
+
 	mutex_lock(&list->read_mutex);
 
 	while (ret == 0) {
@@ -161,9 +185,13 @@  static ssize_t hidraw_send_report(struct file *file, const char __user *buffer,
 
 static ssize_t hidraw_write(struct file *file, const char __user *buffer, size_t count, loff_t *ppos)
 {
+	struct hidraw_list *list = file->private_data;
 	ssize_t ret;
 	down_read(&minors_rwsem);
-	ret = hidraw_send_report(file, buffer, count, HID_OUTPUT_REPORT);
+	if (hidraw_is_revoked(list))
+		ret = -ENODEV;
+	else
+		ret = hidraw_send_report(file, buffer, count, HID_OUTPUT_REPORT);
 	up_read(&minors_rwsem);
 	return ret;
 }
@@ -256,7 +284,7 @@  static __poll_t hidraw_poll(struct file *file, poll_table *wait)
 	poll_wait(file, &list->hidraw->wait, wait);
 	if (list->head != list->tail)
 		mask |= EPOLLIN | EPOLLRDNORM;
-	if (!list->hidraw->exist)
+	if (!list->hidraw->exist || hidraw_is_revoked(list))
 		mask |= EPOLLERR | EPOLLHUP;
 	return mask;
 }
@@ -267,7 +295,11 @@  static int hidraw_open(struct inode *inode, struct file *file)
 	struct hidraw *dev;
 	struct hidraw_list *list;
 	unsigned long flags;
-	int err = 0;
+	int err;
+
+	err = hidraw_open_errno(hidraw_major, minor);
+	if (err < 0)
+		return err;
 
 	if (!(list = kzalloc(sizeof(struct hidraw_list), GFP_KERNEL))) {
 		err = -ENOMEM;
@@ -320,6 +352,9 @@  static int hidraw_fasync(int fd, struct file *file, int on)
 {
 	struct hidraw_list *list = file->private_data;
 
+	if (hidraw_is_revoked(list))
+		return -ENODEV;
+
 	return fasync_helper(fd, file, on, &list->fasync);
 }
 
@@ -372,6 +407,13 @@  static int hidraw_release(struct inode * inode, struct file * file)
 	return 0;
 }
 
+static int hidraw_revoke(struct hidraw_list *list)
+{
+	list->revoked = true;
+
+	return 0;
+}
+
 static long hidraw_ioctl(struct file *file, unsigned int cmd,
 							unsigned long arg)
 {
@@ -379,11 +421,12 @@  static long hidraw_ioctl(struct file *file, unsigned int cmd,
 	unsigned int minor = iminor(inode);
 	long ret = 0;
 	struct hidraw *dev;
+	struct hidraw_list *list = file->private_data;
 	void __user *user_arg = (void __user*) arg;
 
 	down_read(&minors_rwsem);
 	dev = hidraw_table[minor];
-	if (!dev || !dev->exist) {
+	if (!dev || !dev->exist || hidraw_is_revoked(list)) {
 		ret = -ENODEV;
 		goto out;
 	}
@@ -421,6 +464,14 @@  static long hidraw_ioctl(struct file *file, unsigned int cmd,
 					ret = -EFAULT;
 				break;
 			}
+		case HIDIOCREVOKE:
+			{
+				if (user_arg)
+					ret = -EINVAL;
+				else
+					ret = hidraw_revoke(list);
+				break;
+			}
 		default:
 			{
 				struct hid_device *hid = dev->hid;
@@ -527,7 +578,7 @@  int hidraw_report_event(struct hid_device *hid, u8 *data, int len)
 	list_for_each_entry(list, &dev->list, node) {
 		int new_head = (list->head + 1) & (HIDRAW_BUFFER_SIZE - 1);
 
-		if (new_head == list->tail)
+		if (hidraw_is_revoked(list) || new_head == list->tail)
 			continue;
 
 		if (!(list->buffer[list->head].value = kmemdup(data, len, GFP_ATOMIC))) {
diff --git ./include/linux/hidraw.h ../include/linux/hidraw.h
index cd67f4ca5599..18fd30a288de 100644
--- ./include/linux/hidraw.h
+++ ../include/linux/hidraw.h
@@ -32,6 +32,7 @@  struct hidraw_list {
 	struct hidraw *hidraw;
 	struct list_head node;
 	struct mutex read_mutex;
+	bool revoked;
 };
 
 #ifdef CONFIG_HIDRAW
diff --git ./include/uapi/linux/hidraw.h ../include/uapi/linux/hidraw.h
index 33ebad81720a..d0563f251da5 100644
--- ./include/uapi/linux/hidraw.h
+++ ../include/uapi/linux/hidraw.h
@@ -46,6 +46,7 @@  struct hidraw_devinfo {
 /* The first byte of SOUTPUT and GOUTPUT is the report number */
 #define HIDIOCSOUTPUT(len)    _IOC(_IOC_WRITE|_IOC_READ, 'H', 0x0B, len)
 #define HIDIOCGOUTPUT(len)    _IOC(_IOC_WRITE|_IOC_READ, 'H', 0x0C, len)
+#define HIDIOCREVOKE	_IOW('H', 0x0D, int) /* Revoke device access */
 
 #define HIDRAW_FIRST_MINOR 0
 #define HIDRAW_MAX_DEVICES 64