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Commit 2872a9b5 authored by Dmitry Torokhov's avatar Dmitry Torokhov
Browse files

Input: evdev - properly handle read/write with count 0 



According to the standard count 0 is special - no IO should happen but we
can check error conditions (device gone away, etc), and return 0 if there
are no errors. We used to return -EINVAL instead and we also could return 0
if an event was "stolen" by another thread.

Signed-off-by: default avatarDmitry Torokhov <dtor@mail.ru>
parent dba42580

drivers/input/evdev.c

+38 −23
Original line number Diff line number Diff line
@@ -345,7 +345,7 @@ static ssize_t evdev_write(struct file *file, const char __user *buffer, 
	struct input_event event;

	int retval = 0;



	if (count < input_event_size())

	if (count != 0 && count < input_event_size())

		return -EINVAL;



	retval = mutex_lock_interruptible(&evdev->mutex);
@@ -357,7 +357,8 @@ static ssize_t evdev_write(struct file *file, const char __user *buffer, 
		goto out;

	}



	do {

	while (retval + input_event_size() <= count) {



		if (input_event_from_user(buffer + retval, &event)) {

			retval = -EFAULT;

			goto out;
@@ -366,7 +367,7 @@ static ssize_t evdev_write(struct file *file, const char __user *buffer, 


		input_inject_event(&evdev->handle,

				   event.type, event.code, event.value);

	} while (retval + input_event_size() <= count);

	}



 out:

	mutex_unlock(&evdev->mutex);
@@ -397,35 +398,49 @@ static ssize_t evdev_read(struct file *file, char __user *buffer, 
	struct evdev_client *client = file->private_data;

	struct evdev *evdev = client->evdev;

	struct input_event event;

	int retval = 0;

	size_t read = 0;

	int error;



	if (count < input_event_size())

	if (count != 0 && count < input_event_size())

		return -EINVAL;



	if (!(file->f_flags & O_NONBLOCK)) {

		retval = wait_event_interruptible(evdev->wait,

				client->packet_head != client->tail ||

				!evdev->exist);

		if (retval)

			return retval;

	}



	for (;;) {

		if (!evdev->exist)

			return -ENODEV;



	while (retval + input_event_size() <= count &&

		if (client->packet_head == client->tail &&

		    (file->f_flags & O_NONBLOCK))

			return -EAGAIN;



		/*

		 * count == 0 is special - no IO is done but we check

		 * for error conditions (see above).

		 */

		if (count == 0)

			break;



		while (read + input_event_size() <= count &&

		       evdev_fetch_next_event(client, &event)) {



		if (input_event_to_user(buffer + retval, &event))

			if (input_event_to_user(buffer + read, &event))

				return -EFAULT;



		retval += input_event_size();

			read += input_event_size();

		}



	if (retval == 0 && (file->f_flags & O_NONBLOCK))

		return -EAGAIN;

		if (read)

			break;



	return retval;

		if (!(file->f_flags & O_NONBLOCK)) {

			error = wait_event_interruptible(evdev->wait,

					client->packet_head != client->tail ||

					!evdev->exist);

			if (error)

				return error;

		}

	}



	return read;

}



/* No kernel lock - fine */