Revert "ANDROID: input: keychord: Fix races in keychord_write."

This reverts commit 8253552b9900cf4497e1c7d15a83ddc5995abcd8.

Remove keychord driver, replaced in user space by
https://android-review.googlesource.com/c/677629.

Signed-off-by: Mark Salyzyn <salyzyn@google.com>
Bug: 64114943
Bug: 64133562
Bug: 63974334
Bug: 129556081
Change-Id: Ie94621b0adf8b1f8c0d249f74385cc2914b1aec0

diff --git a/drivers/input/misc/keychord.c b/drivers/input/misc/keychord.c
index d679360ded560548b0f3f84f5b60f79a08b08e02..4e0f7daeada63f0859793a1a0dd3bc3ec45feaab 100644 (file)
--- a/drivers/input/misc/keychord.c
+++ b/drivers/input/misc/keychord.c
@@ -60,10 +60,6 @@ struct keychord_device {
        unsigned char           head;
        unsigned char           tail;
        __u16                   buff[BUFFER_SIZE];
-       /* Bit to serialize writes to this device */
-#define KEYCHORD_BUSY                  0x01
-       unsigned long           flags;
-       wait_queue_head_t       write_waitq;
 };
 
 static int check_keychord(struct keychord_device *kdev,
@@ -176,6 +172,7 @@ static int keychord_connect(struct input_handler *handler,
                goto err_input_open_device;
 
        pr_info("keychord: using input dev %s for fevent\n", dev->name);
+
        return 0;
 
 err_input_open_device:
@@ -227,41 +224,6 @@ static ssize_t keychord_read(struct file *file, char __user *buffer,
        return count;
 }
 
-/*
- * serializes writes on a device. can use mutex_lock_interruptible()
- * for this particular use case as well - a matter of preference.
- */
-static int
-keychord_write_lock(struct keychord_device *kdev)
-{
-       int ret;
-       unsigned long flags;
-
-       spin_lock_irqsave(&kdev->lock, flags);
-       while (kdev->flags & KEYCHORD_BUSY) {
-               spin_unlock_irqrestore(&kdev->lock, flags);
-               ret = wait_event_interruptible(kdev->write_waitq,
-                              ((kdev->flags & KEYCHORD_BUSY) == 0));
-               if (ret)
-                       return ret;
-               spin_lock_irqsave(&kdev->lock, flags);
-       }
-       kdev->flags |= KEYCHORD_BUSY;
-       spin_unlock_irqrestore(&kdev->lock, flags);
-       return 0;
-}
-
-static void
-keychord_write_unlock(struct keychord_device *kdev)
-{
-       unsigned long flags;
-
-       spin_lock_irqsave(&kdev->lock, flags);
-       kdev->flags &= ~KEYCHORD_BUSY;
-       spin_unlock_irqrestore(&kdev->lock, flags);
-       wake_up_interruptible(&kdev->write_waitq);
-}
-
 /*
  * keychord_write is used to configure the driver
  */
@@ -288,22 +250,6 @@ static ssize_t keychord_write(struct file *file, const char __user *buffer,
                return -EFAULT;
        }
 
-       /*
-        * Serialize writes to this device to prevent various races.
-        * 1) writers racing here could do duplicate input_unregister_handler()
-        *    calls, resulting in attempting to unlink a node from a list that
-        *    does not exist.
-        * 2) writers racing here could do duplicate input_register_handler() calls
-        *    below, resulting in a duplicate insertion of a node into the list.
-        * 3) a double kfree of keychords can occur (in the event that
-        *    input_register_handler() fails below.
-        */
-       ret = keychord_write_lock(kdev);
-       if (ret) {
-               kfree(keychords);
-               return ret;
-       }
-
        /* unregister handler before changing configuration */
        if (kdev->registered) {
                input_unregister_handler(&kdev->input_handler);
@@ -372,19 +318,15 @@ static ssize_t keychord_write(struct file *file, const char __user *buffer,
        if (ret) {
                kfree(keychords);
                kdev->keychords = 0;
-               keychord_write_unlock(kdev);
                return ret;
        }
        kdev->registered = 1;
 
-       keychord_write_unlock(kdev);
-
        return count;
 
 err_unlock_return:
        spin_unlock_irqrestore(&kdev->lock, flags);
        kfree(keychords);
-       keychord_write_unlock(kdev);
        return -EINVAL;
 }
 
@@ -410,7 +352,6 @@ static int keychord_open(struct inode *inode, struct file *file)
 
        spin_lock_init(&kdev->lock);
        init_waitqueue_head(&kdev->waitq);
-       init_waitqueue_head(&kdev->write_waitq);
 
        kdev->input_handler.event = keychord_event;
        kdev->input_handler.connect = keychord_connect;