linux/drivers/hid/uhid.c

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/*
* User-space I/O driver support for HID subsystem
* Copyright (c) 2012 David Herrmann
*/
/*
* This program is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License as published by the Free
* Software Foundation; either version 2 of the License, or (at your option)
* any later version.
*/
#include <linux/atomic.h>
#include <linux/compat.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;
HID: uhid: fix timeout when probe races with IO Many devices use userspace bluetooth stacks like BlueZ or Bluedroid in combination with uhid. If any of these stacks is used with a HID device for which the driver performs a HID request as part .probe (or technically another HID operation), this results in a deadlock situation. The deadlock results in a 5 second timeout for I/O operations in HID drivers, so isn't fatal, but none of the I/O operations have a chance of succeeding. The root cause for the problem is that uhid only allows for one request to be processed at a time per uhid instance and locks out other operations. This means that if a user space is creating a new HID device through 'UHID_CREATE', which ultimately triggers '.probe' through the HID layer. Then any HID request e.g. a read for calibration data would trigger a HID operation on uhid again, but it won't go out to userspace, because it is still stuck in UHID_CREATE. In addition bluetooth stacks are typically single threaded, so they wouldn't be able to handle any requests while waiting on uhid. Lucikly the UHID spec is somewhat flexible and allows for fixing the issue, without breaking user space. The idea which the patch implements as discussed with David Herrmann is to decouple adding of a hid device (which triggers .probe) from UHID_CREATE. The work will kick off roughly once UHID_CREATE completed (or else will wait a tiny bit of time in .probe for a lock). A HID driver has to call HID to call 'hid_hw_start()' as part of .probe once it is ready for I/O, which triggers UHID_START to user space. Any HID operations should function now within .probe and won't deadlock because userspace is stuck on UHID_CREATE. We verified this patch on Bluedroid with Android 6.0 and on desktop Linux with BlueZ stacks. Prior to the patch they had the deadlock issue. [jkosina@suse.cz: reword subject] Signed-off-by: Roderick Colenbrander <roderick.colenbrander@sony.com> Cc: stable@vger.kernel.org Signed-off-by: Jiri Kosina <jkosina@suse.cz>
2016-05-18 22:11:09 +02:00
struct work_struct worker;
};
static struct miscdevice uhid_misc;
HID: uhid: fix timeout when probe races with IO Many devices use userspace bluetooth stacks like BlueZ or Bluedroid in combination with uhid. If any of these stacks is used with a HID device for which the driver performs a HID request as part .probe (or technically another HID operation), this results in a deadlock situation. The deadlock results in a 5 second timeout for I/O operations in HID drivers, so isn't fatal, but none of the I/O operations have a chance of succeeding. The root cause for the problem is that uhid only allows for one request to be processed at a time per uhid instance and locks out other operations. This means that if a user space is creating a new HID device through 'UHID_CREATE', which ultimately triggers '.probe' through the HID layer. Then any HID request e.g. a read for calibration data would trigger a HID operation on uhid again, but it won't go out to userspace, because it is still stuck in UHID_CREATE. In addition bluetooth stacks are typically single threaded, so they wouldn't be able to handle any requests while waiting on uhid. Lucikly the UHID spec is somewhat flexible and allows for fixing the issue, without breaking user space. The idea which the patch implements as discussed with David Herrmann is to decouple adding of a hid device (which triggers .probe) from UHID_CREATE. The work will kick off roughly once UHID_CREATE completed (or else will wait a tiny bit of time in .probe for a lock). A HID driver has to call HID to call 'hid_hw_start()' as part of .probe once it is ready for I/O, which triggers UHID_START to user space. Any HID operations should function now within .probe and won't deadlock because userspace is stuck on UHID_CREATE. We verified this patch on Bluedroid with Android 6.0 and on desktop Linux with BlueZ stacks. Prior to the patch they had the deadlock issue. [jkosina@suse.cz: reword subject] Signed-off-by: Roderick Colenbrander <roderick.colenbrander@sony.com> Cc: stable@vger.kernel.org Signed-off-by: Jiri Kosina <jkosina@suse.cz>
2016-05-18 22:11:09 +02:00
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);
}
static 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,
};
#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;
}
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;
HID: uhid: fix timeout when probe races with IO Many devices use userspace bluetooth stacks like BlueZ or Bluedroid in combination with uhid. If any of these stacks is used with a HID device for which the driver performs a HID request as part .probe (or technically another HID operation), this results in a deadlock situation. The deadlock results in a 5 second timeout for I/O operations in HID drivers, so isn't fatal, but none of the I/O operations have a chance of succeeding. The root cause for the problem is that uhid only allows for one request to be processed at a time per uhid instance and locks out other operations. This means that if a user space is creating a new HID device through 'UHID_CREATE', which ultimately triggers '.probe' through the HID layer. Then any HID request e.g. a read for calibration data would trigger a HID operation on uhid again, but it won't go out to userspace, because it is still stuck in UHID_CREATE. In addition bluetooth stacks are typically single threaded, so they wouldn't be able to handle any requests while waiting on uhid. Lucikly the UHID spec is somewhat flexible and allows for fixing the issue, without breaking user space. The idea which the patch implements as discussed with David Herrmann is to decouple adding of a hid device (which triggers .probe) from UHID_CREATE. The work will kick off roughly once UHID_CREATE completed (or else will wait a tiny bit of time in .probe for a lock). A HID driver has to call HID to call 'hid_hw_start()' as part of .probe once it is ready for I/O, which triggers UHID_START to user space. Any HID operations should function now within .probe and won't deadlock because userspace is stuck on UHID_CREATE. We verified this patch on Bluedroid with Android 6.0 and on desktop Linux with BlueZ stacks. Prior to the patch they had the deadlock issue. [jkosina@suse.cz: reword subject] Signed-off-by: Roderick Colenbrander <roderick.colenbrander@sony.com> Cc: stable@vger.kernel.org Signed-off-by: Jiri Kosina <jkosina@suse.cz>
2016-05-18 22:11:09 +02:00
/* 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);
HID: uhid: fix timeout when probe races with IO Many devices use userspace bluetooth stacks like BlueZ or Bluedroid in combination with uhid. If any of these stacks is used with a HID device for which the driver performs a HID request as part .probe (or technically another HID operation), this results in a deadlock situation. The deadlock results in a 5 second timeout for I/O operations in HID drivers, so isn't fatal, but none of the I/O operations have a chance of succeeding. The root cause for the problem is that uhid only allows for one request to be processed at a time per uhid instance and locks out other operations. This means that if a user space is creating a new HID device through 'UHID_CREATE', which ultimately triggers '.probe' through the HID layer. Then any HID request e.g. a read for calibration data would trigger a HID operation on uhid again, but it won't go out to userspace, because it is still stuck in UHID_CREATE. In addition bluetooth stacks are typically single threaded, so they wouldn't be able to handle any requests while waiting on uhid. Lucikly the UHID spec is somewhat flexible and allows for fixing the issue, without breaking user space. The idea which the patch implements as discussed with David Herrmann is to decouple adding of a hid device (which triggers .probe) from UHID_CREATE. The work will kick off roughly once UHID_CREATE completed (or else will wait a tiny bit of time in .probe for a lock). A HID driver has to call HID to call 'hid_hw_start()' as part of .probe once it is ready for I/O, which triggers UHID_START to user space. Any HID operations should function now within .probe and won't deadlock because userspace is stuck on UHID_CREATE. We verified this patch on Bluedroid with Android 6.0 and on desktop Linux with BlueZ stacks. Prior to the patch they had the deadlock issue. [jkosina@suse.cz: reword subject] Signed-off-by: Roderick Colenbrander <roderick.colenbrander@sony.com> Cc: stable@vger.kernel.org Signed-off-by: Jiri Kosina <jkosina@suse.cz>
2016-05-18 22:11:09 +02:00
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;
HID: uhid: fix timeout when probe races with IO Many devices use userspace bluetooth stacks like BlueZ or Bluedroid in combination with uhid. If any of these stacks is used with a HID device for which the driver performs a HID request as part .probe (or technically another HID operation), this results in a deadlock situation. The deadlock results in a 5 second timeout for I/O operations in HID drivers, so isn't fatal, but none of the I/O operations have a chance of succeeding. The root cause for the problem is that uhid only allows for one request to be processed at a time per uhid instance and locks out other operations. This means that if a user space is creating a new HID device through 'UHID_CREATE', which ultimately triggers '.probe' through the HID layer. Then any HID request e.g. a read for calibration data would trigger a HID operation on uhid again, but it won't go out to userspace, because it is still stuck in UHID_CREATE. In addition bluetooth stacks are typically single threaded, so they wouldn't be able to handle any requests while waiting on uhid. Lucikly the UHID spec is somewhat flexible and allows for fixing the issue, without breaking user space. The idea which the patch implements as discussed with David Herrmann is to decouple adding of a hid device (which triggers .probe) from UHID_CREATE. The work will kick off roughly once UHID_CREATE completed (or else will wait a tiny bit of time in .probe for a lock). A HID driver has to call HID to call 'hid_hw_start()' as part of .probe once it is ready for I/O, which triggers UHID_START to user space. Any HID operations should function now within .probe and won't deadlock because userspace is stuck on UHID_CREATE. We verified this patch on Bluedroid with Android 6.0 and on desktop Linux with BlueZ stacks. Prior to the patch they had the deadlock issue. [jkosina@suse.cz: reword subject] Signed-off-by: Roderick Colenbrander <roderick.colenbrander@sony.com> Cc: stable@vger.kernel.org Signed-off-by: Jiri Kosina <jkosina@suse.cz>
2016-05-18 22:11:09 +02:00
INIT_WORK(&uhid->worker, uhid_device_add_worker);
file->private_data = uhid;
nonseekable_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:
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 unsigned int uhid_char_poll(struct file *file, poll_table *wait)
{
struct uhid_device *uhid = file->private_data;
poll_wait(file, &uhid->waitq, wait);
if (uhid->head != uhid->tail)
return POLLIN | POLLRDNORM;
return 0;
}
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,
};
static int __init uhid_init(void)
{
return misc_register(&uhid_misc);
}
static void __exit uhid_exit(void)
{
misc_deregister(&uhid_misc);
}
module_init(uhid_init);
module_exit(uhid_exit);
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);