// SPDX-License-Identifier: GPL-2.0-or-later /* * User-space I/O driver support for HID subsystem * Copyright (c) 2012 David Herrmann */ /* */ #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #define UHID_NAME "uhid" #define UHID_BUFSIZE 32 struct uhid_device { struct mutex devlock; /* This flag tracks whether the HID device is usable for commands from * userspace. The flag is already set before hid_add_device(), which * runs in workqueue context, to allow hid_add_device() to communicate * with userspace. * However, if hid_add_device() fails, the flag is cleared without * holding devlock. * We guarantee that if @running changes from true to false while you're * holding @devlock, it's still fine to access @hid. */ bool running; __u8 *rd_data; uint rd_size; /* When this is NULL, userspace may use UHID_CREATE/UHID_CREATE2. */ 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); /* We used to call hid_destroy_device() here, but that's really * messy to get right because we have to coordinate with * concurrent writes from userspace that might be in the middle * of using uhid->hid. * Just leave uhid->hid as-is for now, and clean it up when * userspace tries to close or reinitialize the uhid instance. * * However, we do have to clear the ->running flag and do a * wakeup to make sure userspace knows that the device is gone. */ WRITE_ONCE(uhid->running, false); wake_up_interruptible(&uhid->report_wait); } } 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 || !READ_ONCE(uhid->running), 5 * HZ); if (!ret || !READ_ONCE(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 (!READ_ONCE(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 (!READ_ONCE(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->hid) 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->hid) return -EINVAL; WRITE_ONCE(uhid->running, false); wake_up_interruptible(&uhid->report_wait); cancel_work_sync(&uhid->worker); hid_destroy_device(uhid->hid); uhid->hid = NULL; kfree(uhid->rd_data); return 0; } static int uhid_dev_input(struct uhid_device *uhid, struct uhid_event *ev) { if (!READ_ONCE(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 (!READ_ONCE(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 (!READ_ONCE(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 (!READ_ONCE(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()) { 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 "); MODULE_DESCRIPTION("User-space I/O driver support for HID subsystem"); MODULE_ALIAS_MISCDEV(UHID_MINOR); MODULE_ALIAS("devname:" UHID_NAME);