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Commit 486c8aba authored by Dmitry Torokhov's avatar Dmitry Torokhov
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Input: serio_raw - ensure we don't block in non-blocking read 



Avoid calling wait_event_interruptible() if client requested non-blocking
read, since it is not guaranteed that another thread will not consume
event after we checked if serio_raw->head != serio_raw->tail.

Also ensure we do not return 0 but keep waiting instead in blocking case,
when another thread steals "our" byte.

Reviewed-by: default avatarDavid Herrmann <dh.herrmann@googlemail.com>
Reviewed-by: default avatarChe-Liang Chiou <clchiou@chromium.org>
Signed-off-by: default avatarDmitry Torokhov <dtor@mail.ru>
parent 71f3d070

drivers/input/serio/serio_raw.c

+25 −18
Original line number Diff line number Diff line
@@ -165,31 +165,38 @@ static ssize_t serio_raw_read(struct file *file, char __user *buffer, 
	struct serio_raw *serio_raw = client->serio_raw;

	char uninitialized_var(c);

	ssize_t read = 0;

	int retval;

	int error = 0;



	do {

		if (serio_raw->dead)

			return -ENODEV;



	if (serio_raw->head == serio_raw->tail && (file->f_flags & O_NONBLOCK))

		if (serio_raw->head == serio_raw->tail &&

		    (file->f_flags & O_NONBLOCK))

			return -EAGAIN;



	retval = wait_event_interruptible(serio_raw->wait,

			serio_raw->head != serio_raw->tail || serio_raw->dead);

	if (retval)

		return retval;



	if (serio_raw->dead)

		return -ENODEV;

		if (count == 0)

			break;



		while (read < count && serio_raw_fetch_byte(serio_raw, &c)) {

			if (put_user(c, buffer++)) {

			retval = -EFAULT;

			break;

				error = -EFAULT;

				goto out;

			}

			read++;

		}



	return read ?: retval;

		if (read)

			break;



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

			error = wait_event_interruptible(serio_raw->wait,

					serio_raw->head != serio_raw->tail ||

					serio_raw->dead);

	} while (!error);



out:

	return read ?: error;

}



static ssize_t serio_raw_write(struct file *file, const char __user *buffer,