uhid.c
// SPDX-License-Identifier: GPL-2.0-or-later
/*
* User-space I/O driver support for HID subsystem
* Copyright (c) 2012 David Herrmann
*/
/*
*/
#include <linux/atomic.h>
#include <linux/compat.h>
#include <linux/cred.h>
#include <linux/device.h>
#include <linux/fs.h>
#include <linux/hid.h>
#include <linux/input.h>
#include <linux/miscdevice.h>
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/poll.h>
#include <linux/sched.h>
#include <linux/spinlock.h>
#include <linux/uhid.h>
#include <linux/wait.h>
#define UHID_NAME "uhid"
#define UHID_BUFSIZE 32
struct uhid_device {
struct mutex devlock;
bool running;
__u8 *rd_data;
uint rd_size;
struct hid_device *hid;
struct uhid_event input_buf;
wait_queue_head_t waitq;
spinlock_t qlock;
__u8 head;
__u8 tail;
struct uhid_event *outq[UHID_BUFSIZE];
/* blocking GET_REPORT support; state changes protected by qlock */
struct mutex report_lock;
wait_queue_head_t report_wait;
bool report_running;
u32 report_id;
u32 report_type;
struct uhid_event report_buf;
struct work_struct worker;
};
static struct miscdevice uhid_misc;
static void uhid_device_add_worker(struct work_struct *work)
{
struct uhid_device *uhid = container_of(work, struct uhid_device, worker);
int ret;
ret = hid_add_device(uhid->hid);
if (ret) {
hid_err(uhid->hid, "Cannot register HID device: error %d\n", ret);
hid_destroy_device(uhid->hid);
uhid->hid = NULL;
uhid->running = false;
}
}
static void uhid_queue(struct uhid_device *uhid, struct uhid_event *ev)
{
__u8 newhead;
newhead = (uhid->head + 1) % UHID_BUFSIZE;
if (newhead != uhid->tail) {
uhid->outq[uhid->head] = ev;
uhid->head = newhead;
wake_up_interruptible(&uhid->waitq);
} else {
hid_warn(uhid->hid, "Output queue is full\n");
kfree(ev);
}
}
static int uhid_queue_event(struct uhid_device *uhid, __u32 event)
{
unsigned long flags;
struct uhid_event *ev;
ev = kzalloc(sizeof(*ev), GFP_KERNEL);
if (!ev)
return -ENOMEM;
ev->type = event;
spin_lock_irqsave(&uhid->qlock, flags);
uhid_queue(uhid, ev);
spin_unlock_irqrestore(&uhid->qlock, flags);
return 0;
}
static int uhid_hid_start(struct hid_device *hid)
{
struct uhid_device *uhid = hid->driver_data;
struct uhid_event *ev;
unsigned long flags;
ev = kzalloc(sizeof(*ev), GFP_KERNEL);
if (!ev)
return -ENOMEM;
ev->type = UHID_START;
if (hid->report_enum[HID_FEATURE_REPORT].numbered)
ev->u.start.dev_flags |= UHID_DEV_NUMBERED_FEATURE_REPORTS;
if (hid->report_enum[HID_OUTPUT_REPORT].numbered)
ev->u.start.dev_flags |= UHID_DEV_NUMBERED_OUTPUT_REPORTS;
if (hid->report_enum[HID_INPUT_REPORT].numbered)
ev->u.start.dev_flags |= UHID_DEV_NUMBERED_INPUT_REPORTS;
spin_lock_irqsave(&uhid->qlock, flags);
uhid_queue(uhid, ev);
spin_unlock_irqrestore(&uhid->qlock, flags);
return 0;
}
static void uhid_hid_stop(struct hid_device *hid)
{
struct uhid_device *uhid = hid->driver_data;
hid->claimed = 0;
uhid_queue_event(uhid, UHID_STOP);
}
static int uhid_hid_open(struct hid_device *hid)
{
struct uhid_device *uhid = hid->driver_data;
return uhid_queue_event(uhid, UHID_OPEN);
}
static void uhid_hid_close(struct hid_device *hid)
{
struct uhid_device *uhid = hid->driver_data;
uhid_queue_event(uhid, UHID_CLOSE);
}
static int uhid_hid_parse(struct hid_device *hid)
{
struct uhid_device *uhid = hid->driver_data;
return hid_parse_report(hid, uhid->rd_data, uhid->rd_size);
}
/* must be called with report_lock held */
static int __uhid_report_queue_and_wait(struct uhid_device *uhid,
struct uhid_event *ev,
__u32 *report_id)
{
unsigned long flags;
int ret;
spin_lock_irqsave(&uhid->qlock, flags);
*report_id = ++uhid->report_id;
uhid->report_type = ev->type + 1;
uhid->report_running = true;
uhid_queue(uhid, ev);
spin_unlock_irqrestore(&uhid->qlock, flags);
ret = wait_event_interruptible_timeout(uhid->report_wait,
!uhid->report_running || !uhid->running,
5 * HZ);
if (!ret || !uhid->running || uhid->report_running)
ret = -EIO;
else if (ret < 0)
ret = -ERESTARTSYS;
else
ret = 0;
uhid->report_running = false;
return ret;
}
static void uhid_report_wake_up(struct uhid_device *uhid, u32 id,
const struct uhid_event *ev)
{
unsigned long flags;
spin_lock_irqsave(&uhid->qlock, flags);
/* id for old report; drop it silently */
if (uhid->report_type != ev->type || uhid->report_id != id)
goto unlock;
if (!uhid->report_running)
goto unlock;
memcpy(&uhid->report_buf, ev, sizeof(*ev));
uhid->report_running = false;
wake_up_interruptible(&uhid->report_wait);
unlock:
spin_unlock_irqrestore(&uhid->qlock, flags);
}
static int uhid_hid_get_report(struct hid_device *hid, unsigned char rnum,
u8 *buf, size_t count, u8 rtype)
{
struct uhid_device *uhid = hid->driver_data;
struct uhid_get_report_reply_req *req;
struct uhid_event *ev;
int ret;
if (!uhid->running)
return -EIO;
ev = kzalloc(sizeof(*ev), GFP_KERNEL);
if (!ev)
return -ENOMEM;
ev->type = UHID_GET_REPORT;
ev->u.get_report.rnum = rnum;
ev->u.get_report.rtype = rtype;
ret = mutex_lock_interruptible(&uhid->report_lock);
if (ret) {
kfree(ev);
return ret;
}
/* this _always_ takes ownership of @ev */
ret = __uhid_report_queue_and_wait(uhid, ev, &ev->u.get_report.id);
if (ret)
goto unlock;
req = &uhid->report_buf.u.get_report_reply;
if (req->err) {
ret = -EIO;
} else {
ret = min3(count, (size_t)req->size, (size_t)UHID_DATA_MAX);
memcpy(buf, req->data, ret);
}
unlock:
mutex_unlock(&uhid->report_lock);
return ret;
}
static int uhid_hid_set_report(struct hid_device *hid, unsigned char rnum,
const u8 *buf, size_t count, u8 rtype)
{
struct uhid_device *uhid = hid->driver_data;
struct uhid_event *ev;
int ret;
if (!uhid->running || count > UHID_DATA_MAX)
return -EIO;
ev = kzalloc(sizeof(*ev), GFP_KERNEL);
if (!ev)
return -ENOMEM;
ev->type = UHID_SET_REPORT;
ev->u.set_report.rnum = rnum;
ev->u.set_report.rtype = rtype;
ev->u.set_report.size = count;
memcpy(ev->u.set_report.data, buf, count);
ret = mutex_lock_interruptible(&uhid->report_lock);
if (ret) {
kfree(ev);
return ret;
}
/* this _always_ takes ownership of @ev */
ret = __uhid_report_queue_and_wait(uhid, ev, &ev->u.set_report.id);
if (ret)
goto unlock;
if (uhid->report_buf.u.set_report_reply.err)
ret = -EIO;
else
ret = count;
unlock:
mutex_unlock(&uhid->report_lock);
return ret;
}
static int uhid_hid_raw_request(struct hid_device *hid, unsigned char reportnum,
__u8 *buf, size_t len, unsigned char rtype,
int reqtype)
{
u8 u_rtype;
switch (rtype) {
case HID_FEATURE_REPORT:
u_rtype = UHID_FEATURE_REPORT;
break;
case HID_OUTPUT_REPORT:
u_rtype = UHID_OUTPUT_REPORT;
break;
case HID_INPUT_REPORT:
u_rtype = UHID_INPUT_REPORT;
break;
default:
return -EINVAL;
}
switch (reqtype) {
case HID_REQ_GET_REPORT:
return uhid_hid_get_report(hid, reportnum, buf, len, u_rtype);
case HID_REQ_SET_REPORT:
return uhid_hid_set_report(hid, reportnum, buf, len, u_rtype);
default:
return -EIO;
}
}
static int uhid_hid_output_raw(struct hid_device *hid, __u8 *buf, size_t count,
unsigned char report_type)
{
struct uhid_device *uhid = hid->driver_data;
__u8 rtype;
unsigned long flags;
struct uhid_event *ev;
switch (report_type) {
case HID_FEATURE_REPORT:
rtype = UHID_FEATURE_REPORT;
break;
case HID_OUTPUT_REPORT:
rtype = UHID_OUTPUT_REPORT;
break;
default:
return -EINVAL;
}
if (count < 1 || count > UHID_DATA_MAX)
return -EINVAL;
ev = kzalloc(sizeof(*ev), GFP_KERNEL);
if (!ev)
return -ENOMEM;
ev->type = UHID_OUTPUT;
ev->u.output.size = count;
ev->u.output.rtype = rtype;
memcpy(ev->u.output.data, buf, count);
spin_lock_irqsave(&uhid->qlock, flags);
uhid_queue(uhid, ev);
spin_unlock_irqrestore(&uhid->qlock, flags);
return count;
}
static int uhid_hid_output_report(struct hid_device *hid, __u8 *buf,
size_t count)
{
return uhid_hid_output_raw(hid, buf, count, HID_OUTPUT_REPORT);
}
struct hid_ll_driver uhid_hid_driver = {
.start = uhid_hid_start,
.stop = uhid_hid_stop,
.open = uhid_hid_open,
.close = uhid_hid_close,
.parse = uhid_hid_parse,
.raw_request = uhid_hid_raw_request,
.output_report = uhid_hid_output_report,
};
EXPORT_SYMBOL_GPL(uhid_hid_driver);
#ifdef CONFIG_COMPAT
/* Apparently we haven't stepped on these rakes enough times yet. */
struct uhid_create_req_compat {
__u8 name[128];
__u8 phys[64];
__u8 uniq[64];
compat_uptr_t rd_data;
__u16 rd_size;
__u16 bus;
__u32 vendor;
__u32 product;
__u32 version;
__u32 country;
} __attribute__((__packed__));
static int uhid_event_from_user(const char __user *buffer, size_t len,
struct uhid_event *event)
{
if (in_compat_syscall()) {
u32 type;
if (get_user(type, buffer))
return -EFAULT;
if (type == UHID_CREATE) {
/*
* This is our messed up request with compat pointer.
* It is largish (more than 256 bytes) so we better
* allocate it from the heap.
*/
struct uhid_create_req_compat *compat;
compat = kzalloc(sizeof(*compat), GFP_KERNEL);
if (!compat)
return -ENOMEM;
buffer += sizeof(type);
len -= sizeof(type);
if (copy_from_user(compat, buffer,
min(len, sizeof(*compat)))) {
kfree(compat);
return -EFAULT;
}
/* Shuffle the data over to proper structure */
event->type = type;
memcpy(event->u.create.name, compat->name,
sizeof(compat->name));
memcpy(event->u.create.phys, compat->phys,
sizeof(compat->phys));
memcpy(event->u.create.uniq, compat->uniq,
sizeof(compat->uniq));
event->u.create.rd_data = compat_ptr(compat->rd_data);
event->u.create.rd_size = compat->rd_size;
event->u.create.bus = compat->bus;
event->u.create.vendor = compat->vendor;
event->u.create.product = compat->product;
event->u.create.version = compat->version;
event->u.create.country = compat->country;
kfree(compat);
return 0;
}
/* All others can be copied directly */
}
if (copy_from_user(event, buffer, min(len, sizeof(*event))))
return -EFAULT;
return 0;
}
#else
static int uhid_event_from_user(const char __user *buffer, size_t len,
struct uhid_event *event)
{
if (copy_from_user(event, buffer, min(len, sizeof(*event))))
return -EFAULT;
return 0;
}
#endif
static int uhid_dev_create2(struct uhid_device *uhid,
const struct uhid_event *ev)
{
struct hid_device *hid;
size_t rd_size, len;
void *rd_data;
int ret;
if (uhid->running)
return -EALREADY;
rd_size = ev->u.create2.rd_size;
if (rd_size <= 0 || rd_size > HID_MAX_DESCRIPTOR_SIZE)
return -EINVAL;
rd_data = kmemdup(ev->u.create2.rd_data, rd_size, GFP_KERNEL);
if (!rd_data)
return -ENOMEM;
uhid->rd_size = rd_size;
uhid->rd_data = rd_data;
hid = hid_allocate_device();
if (IS_ERR(hid)) {
ret = PTR_ERR(hid);
goto err_free;
}
/* @hid is zero-initialized, strncpy() is correct, strlcpy() not */
len = min(sizeof(hid->name), sizeof(ev->u.create2.name)) - 1;
strncpy(hid->name, ev->u.create2.name, len);
len = min(sizeof(hid->phys), sizeof(ev->u.create2.phys)) - 1;
strncpy(hid->phys, ev->u.create2.phys, len);
len = min(sizeof(hid->uniq), sizeof(ev->u.create2.uniq)) - 1;
strncpy(hid->uniq, ev->u.create2.uniq, len);
hid->ll_driver = &uhid_hid_driver;
hid->bus = ev->u.create2.bus;
hid->vendor = ev->u.create2.vendor;
hid->product = ev->u.create2.product;
hid->version = ev->u.create2.version;
hid->country = ev->u.create2.country;
hid->driver_data = uhid;
hid->dev.parent = uhid_misc.this_device;
uhid->hid = hid;
uhid->running = true;
/* Adding of a HID device is done through a worker, to allow HID drivers
* which use feature requests during .probe to work, without they would
* be blocked on devlock, which is held by uhid_char_write.
*/
schedule_work(&uhid->worker);
return 0;
err_free:
kfree(uhid->rd_data);
uhid->rd_data = NULL;
uhid->rd_size = 0;
return ret;
}
static int uhid_dev_create(struct uhid_device *uhid,
struct uhid_event *ev)
{
struct uhid_create_req orig;
orig = ev->u.create;
if (orig.rd_size <= 0 || orig.rd_size > HID_MAX_DESCRIPTOR_SIZE)
return -EINVAL;
if (copy_from_user(&ev->u.create2.rd_data, orig.rd_data, orig.rd_size))
return -EFAULT;
memcpy(ev->u.create2.name, orig.name, sizeof(orig.name));
memcpy(ev->u.create2.phys, orig.phys, sizeof(orig.phys));
memcpy(ev->u.create2.uniq, orig.uniq, sizeof(orig.uniq));
ev->u.create2.rd_size = orig.rd_size;
ev->u.create2.bus = orig.bus;
ev->u.create2.vendor = orig.vendor;
ev->u.create2.product = orig.product;
ev->u.create2.version = orig.version;
ev->u.create2.country = orig.country;
return uhid_dev_create2(uhid, ev);
}
static int uhid_dev_destroy(struct uhid_device *uhid)
{
if (!uhid->running)
return -EINVAL;
uhid->running = false;
wake_up_interruptible(&uhid->report_wait);
cancel_work_sync(&uhid->worker);
hid_destroy_device(uhid->hid);
kfree(uhid->rd_data);
return 0;
}
static int uhid_dev_input(struct uhid_device *uhid, struct uhid_event *ev)
{
if (!uhid->running)
return -EINVAL;
hid_input_report(uhid->hid, HID_INPUT_REPORT, ev->u.input.data,
min_t(size_t, ev->u.input.size, UHID_DATA_MAX), 0);
return 0;
}
static int uhid_dev_input2(struct uhid_device *uhid, struct uhid_event *ev)
{
if (!uhid->running)
return -EINVAL;
hid_input_report(uhid->hid, HID_INPUT_REPORT, ev->u.input2.data,
min_t(size_t, ev->u.input2.size, UHID_DATA_MAX), 0);
return 0;
}
static int uhid_dev_get_report_reply(struct uhid_device *uhid,
struct uhid_event *ev)
{
if (!uhid->running)
return -EINVAL;
uhid_report_wake_up(uhid, ev->u.get_report_reply.id, ev);
return 0;
}
static int uhid_dev_set_report_reply(struct uhid_device *uhid,
struct uhid_event *ev)
{
if (!uhid->running)
return -EINVAL;
uhid_report_wake_up(uhid, ev->u.set_report_reply.id, ev);
return 0;
}
static int uhid_char_open(struct inode *inode, struct file *file)
{
struct uhid_device *uhid;
uhid = kzalloc(sizeof(*uhid), GFP_KERNEL);
if (!uhid)
return -ENOMEM;
mutex_init(&uhid->devlock);
mutex_init(&uhid->report_lock);
spin_lock_init(&uhid->qlock);
init_waitqueue_head(&uhid->waitq);
init_waitqueue_head(&uhid->report_wait);
uhid->running = false;
INIT_WORK(&uhid->worker, uhid_device_add_worker);
file->private_data = uhid;
stream_open(inode, file);
return 0;
}
static int uhid_char_release(struct inode *inode, struct file *file)
{
struct uhid_device *uhid = file->private_data;
unsigned int i;
uhid_dev_destroy(uhid);
for (i = 0; i < UHID_BUFSIZE; ++i)
kfree(uhid->outq[i]);
kfree(uhid);
return 0;
}
static ssize_t uhid_char_read(struct file *file, char __user *buffer,
size_t count, loff_t *ppos)
{
struct uhid_device *uhid = file->private_data;
int ret;
unsigned long flags;
size_t len;
/* they need at least the "type" member of uhid_event */
if (count < sizeof(__u32))
return -EINVAL;
try_again:
if (file->f_flags & O_NONBLOCK) {
if (uhid->head == uhid->tail)
return -EAGAIN;
} else {
ret = wait_event_interruptible(uhid->waitq,
uhid->head != uhid->tail);
if (ret)
return ret;
}
ret = mutex_lock_interruptible(&uhid->devlock);
if (ret)
return ret;
if (uhid->head == uhid->tail) {
mutex_unlock(&uhid->devlock);
goto try_again;
} else {
len = min(count, sizeof(**uhid->outq));
if (copy_to_user(buffer, uhid->outq[uhid->tail], len)) {
ret = -EFAULT;
} else {
kfree(uhid->outq[uhid->tail]);
uhid->outq[uhid->tail] = NULL;
spin_lock_irqsave(&uhid->qlock, flags);
uhid->tail = (uhid->tail + 1) % UHID_BUFSIZE;
spin_unlock_irqrestore(&uhid->qlock, flags);
}
}
mutex_unlock(&uhid->devlock);
return ret ? ret : len;
}
static ssize_t uhid_char_write(struct file *file, const char __user *buffer,
size_t count, loff_t *ppos)
{
struct uhid_device *uhid = file->private_data;
int ret;
size_t len;
/* we need at least the "type" member of uhid_event */
if (count < sizeof(__u32))
return -EINVAL;
ret = mutex_lock_interruptible(&uhid->devlock);
if (ret)
return ret;
memset(&uhid->input_buf, 0, sizeof(uhid->input_buf));
len = min(count, sizeof(uhid->input_buf));
ret = uhid_event_from_user(buffer, len, &uhid->input_buf);
if (ret)
goto unlock;
switch (uhid->input_buf.type) {
case UHID_CREATE:
/*
* 'struct uhid_create_req' contains a __user pointer which is
* copied from, so it's unsafe to allow this with elevated
* privileges (e.g. from a setuid binary) or via kernel_write().
*/
if (file->f_cred != current_cred() || uaccess_kernel()) {
pr_err_once("UHID_CREATE from different security context by process %d (%s), this is not allowed.\n",
task_tgid_vnr(current), current->comm);
ret = -EACCES;
goto unlock;
}
ret = uhid_dev_create(uhid, &uhid->input_buf);
break;
case UHID_CREATE2:
ret = uhid_dev_create2(uhid, &uhid->input_buf);
break;
case UHID_DESTROY:
ret = uhid_dev_destroy(uhid);
break;
case UHID_INPUT:
ret = uhid_dev_input(uhid, &uhid->input_buf);
break;
case UHID_INPUT2:
ret = uhid_dev_input2(uhid, &uhid->input_buf);
break;
case UHID_GET_REPORT_REPLY:
ret = uhid_dev_get_report_reply(uhid, &uhid->input_buf);
break;
case UHID_SET_REPORT_REPLY:
ret = uhid_dev_set_report_reply(uhid, &uhid->input_buf);
break;
default:
ret = -EOPNOTSUPP;
}
unlock:
mutex_unlock(&uhid->devlock);
/* return "count" not "len" to not confuse the caller */
return ret ? ret : count;
}
static __poll_t uhid_char_poll(struct file *file, poll_table *wait)
{
struct uhid_device *uhid = file->private_data;
__poll_t mask = EPOLLOUT | EPOLLWRNORM; /* uhid is always writable */
poll_wait(file, &uhid->waitq, wait);
if (uhid->head != uhid->tail)
mask |= EPOLLIN | EPOLLRDNORM;
return mask;
}
static const struct file_operations uhid_fops = {
.owner = THIS_MODULE,
.open = uhid_char_open,
.release = uhid_char_release,
.read = uhid_char_read,
.write = uhid_char_write,
.poll = uhid_char_poll,
.llseek = no_llseek,
};
static struct miscdevice uhid_misc = {
.fops = &uhid_fops,
.minor = UHID_MINOR,
.name = UHID_NAME,
};
module_misc_device(uhid_misc);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("David Herrmann <dh.herrmann@gmail.com>");
MODULE_DESCRIPTION("User-space I/O driver support for HID subsystem");
MODULE_ALIAS_MISCDEV(UHID_MINOR);
MODULE_ALIAS("devname:" UHID_NAME);