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HID: debug: fix the ring buffer implementation
Ring buffer implementation in hid_debug_event() and hid_debug_events_read() is strange allowing lost or corrupted data. After commit717adfdaf1("HID: debug: check length before copy_to_user()") it is possible to enter an infinite loop in hid_debug_events_read() by providing 0 as count, this locks up a system. Fix this by rewriting the ring buffer implementation with kfifo and simplify the code. This fixes CVE-2019-3819. v2: fix an execution logic and add a comment v3: use __set_current_state() instead of set_current_state() Link: https://bugzilla.redhat.com/show_bug.cgi?id=1669187 Cc: stable@vger.kernel.org # v4.18+ Fixes:cd667ce247("HID: use debugfs for events/reports dumping") Fixes:717adfdaf1("HID: debug: check length before copy_to_user()") Signed-off-by: Vladis Dronov <vdronov@redhat.com> Reviewed-by: Oleg Nesterov <oleg@redhat.com> Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
This commit is contained in:
Vladis Dronov
Benjamin Tissoires
parent
1950f46291
commit
13054abbaa
@ -30,6 +30,7 @@
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#include <linux/debugfs.h>
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#include <linux/seq_file.h>
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#include <linux/kfifo.h>
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#include <linux/sched/signal.h>
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#include <linux/export.h>
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#include <linux/slab.h>
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@ -661,17 +662,12 @@ EXPORT_SYMBOL_GPL(hid_dump_device);
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/* enqueue string to 'events' ring buffer */
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void hid_debug_event(struct hid_device *hdev, char *buf)
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{
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unsigned i;
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struct hid_debug_list *list;
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unsigned long flags;
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spin_lock_irqsave(&hdev->debug_list_lock, flags);
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list_for_each_entry(list, &hdev->debug_list, node) {
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for (i = 0; buf[i]; i++)
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list->hid_debug_buf[(list->tail + i) % HID_DEBUG_BUFSIZE] =
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buf[i];
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list->tail = (list->tail + i) % HID_DEBUG_BUFSIZE;
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}
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list_for_each_entry(list, &hdev->debug_list, node)
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kfifo_in(&list->hid_debug_fifo, buf, strlen(buf));
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spin_unlock_irqrestore(&hdev->debug_list_lock, flags);
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wake_up_interruptible(&hdev->debug_wait);
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@ -722,8 +718,7 @@ void hid_dump_input(struct hid_device *hdev, struct hid_usage *usage, __s32 valu
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hid_debug_event(hdev, buf);
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kfree(buf);
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wake_up_interruptible(&hdev->debug_wait);
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wake_up_interruptible(&hdev->debug_wait);
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}
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EXPORT_SYMBOL_GPL(hid_dump_input);
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@ -1083,8 +1078,8 @@ static int hid_debug_events_open(struct inode *inode, struct file *file)
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goto out;
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}
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if (!(list->hid_debug_buf = kzalloc(HID_DEBUG_BUFSIZE, GFP_KERNEL))) {
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err = -ENOMEM;
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err = kfifo_alloc(&list->hid_debug_fifo, HID_DEBUG_FIFOSIZE, GFP_KERNEL);
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if (err) {
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kfree(list);
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goto out;
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}
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@ -1104,77 +1099,57 @@ static ssize_t hid_debug_events_read(struct file *file, char __user *buffer,
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size_t count, loff_t *ppos)
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{
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struct hid_debug_list *list = file->private_data;
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int ret = 0, len;
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int ret = 0, copied;
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DECLARE_WAITQUEUE(wait, current);
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mutex_lock(&list->read_mutex);
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while (ret == 0) {
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if (list->head == list->tail) {
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add_wait_queue(&list->hdev->debug_wait, &wait);
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set_current_state(TASK_INTERRUPTIBLE);
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if (kfifo_is_empty(&list->hid_debug_fifo)) {
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add_wait_queue(&list->hdev->debug_wait, &wait);
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set_current_state(TASK_INTERRUPTIBLE);
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while (list->head == list->tail) {
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if (file->f_flags & O_NONBLOCK) {
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ret = -EAGAIN;
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break;
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}
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if (signal_pending(current)) {
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ret = -ERESTARTSYS;
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break;
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}
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if (!list->hdev || !list->hdev->debug) {
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ret = -EIO;
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set_current_state(TASK_RUNNING);
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goto out;
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}
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/* allow O_NONBLOCK from other threads */
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mutex_unlock(&list->read_mutex);
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schedule();
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mutex_lock(&list->read_mutex);
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set_current_state(TASK_INTERRUPTIBLE);
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while (kfifo_is_empty(&list->hid_debug_fifo)) {
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if (file->f_flags & O_NONBLOCK) {
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ret = -EAGAIN;
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break;
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}
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set_current_state(TASK_RUNNING);
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remove_wait_queue(&list->hdev->debug_wait, &wait);
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if (signal_pending(current)) {
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ret = -ERESTARTSYS;
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break;
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}
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/* if list->hdev is NULL we cannot remove_wait_queue().
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* if list->hdev->debug is 0 then hid_debug_unregister()
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* was already called and list->hdev is being destroyed.
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* if we add remove_wait_queue() here we can hit a race.
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*/
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if (!list->hdev || !list->hdev->debug) {
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ret = -EIO;
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set_current_state(TASK_RUNNING);
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goto out;
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}
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/* allow O_NONBLOCK from other threads */
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mutex_unlock(&list->read_mutex);
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schedule();
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mutex_lock(&list->read_mutex);
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set_current_state(TASK_INTERRUPTIBLE);
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}
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__set_current_state(TASK_RUNNING);
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remove_wait_queue(&list->hdev->debug_wait, &wait);
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if (ret)
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goto out;
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/* pass the ringbuffer contents to userspace */
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copy_rest:
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if (list->tail == list->head)
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goto out;
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if (list->tail > list->head) {
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len = list->tail - list->head;
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if (len > count)
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len = count;
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if (copy_to_user(buffer + ret, &list->hid_debug_buf[list->head], len)) {
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ret = -EFAULT;
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goto out;
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}
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ret += len;
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list->head += len;
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} else {
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len = HID_DEBUG_BUFSIZE - list->head;
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if (len > count)
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len = count;
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if (copy_to_user(buffer, &list->hid_debug_buf[list->head], len)) {
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ret = -EFAULT;
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goto out;
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}
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list->head = 0;
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ret += len;
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count -= len;
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if (count > 0)
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goto copy_rest;
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}
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}
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/* pass the fifo content to userspace, locking is not needed with only
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* one concurrent reader and one concurrent writer
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*/
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ret = kfifo_to_user(&list->hid_debug_fifo, buffer, count, &copied);
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if (ret)
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goto out;
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ret = copied;
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out:
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mutex_unlock(&list->read_mutex);
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return ret;
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@ -1185,7 +1160,7 @@ static __poll_t hid_debug_events_poll(struct file *file, poll_table *wait)
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struct hid_debug_list *list = file->private_data;
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poll_wait(file, &list->hdev->debug_wait, wait);
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if (list->head != list->tail)
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if (!kfifo_is_empty(&list->hid_debug_fifo))
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return EPOLLIN | EPOLLRDNORM;
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if (!list->hdev->debug)
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return EPOLLERR | EPOLLHUP;
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@ -1200,7 +1175,7 @@ static int hid_debug_events_release(struct inode *inode, struct file *file)
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spin_lock_irqsave(&list->hdev->debug_list_lock, flags);
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list_del(&list->node);
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spin_unlock_irqrestore(&list->hdev->debug_list_lock, flags);
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kfree(list->hid_debug_buf);
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kfifo_free(&list->hid_debug_fifo);
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kfree(list);
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return 0;
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@ -1246,4 +1221,3 @@ void hid_debug_exit(void)
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{
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debugfs_remove_recursive(hid_debug_root);
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}
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@ -24,7 +24,10 @@
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#ifdef CONFIG_DEBUG_FS
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#include <linux/kfifo.h>
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#define HID_DEBUG_BUFSIZE 512
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#define HID_DEBUG_FIFOSIZE 512
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void hid_dump_input(struct hid_device *, struct hid_usage *, __s32);
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void hid_dump_report(struct hid_device *, int , u8 *, int);
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@ -37,11 +40,8 @@ void hid_debug_init(void);
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void hid_debug_exit(void);
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void hid_debug_event(struct hid_device *, char *);
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struct hid_debug_list {
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char *hid_debug_buf;
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int head;
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int tail;
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DECLARE_KFIFO_PTR(hid_debug_fifo, char);
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struct fasync_struct *fasync;
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struct hid_device *hdev;
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struct list_head node;
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@ -64,4 +64,3 @@ struct hid_debug_list {
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#endif
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#endif
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