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Commit aebf0453 authored by Peter Hurley's avatar Peter Hurley Committed by Greg Kroah-Hartman
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n_tty: Protect minimum_to_wake reset for concurrent readers 



With multiple, concurrent readers (each waiting to acquire the
atomic_read_lock mutex), a departing reader may mistakenly reset
minimum_to_wake after a new reader has already set a new value.

Protect the minimum_to_wake reset with the atomic_read_lock critical
section.

Signed-off-by: default avatarPeter Hurley <peter@hurleysoftware.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent d4855e1f

drivers/tty/n_tty.c

+2 −2
Original line number Diff line number Diff line
@@ -2249,12 +2249,12 @@ static ssize_t n_tty_read(struct tty_struct *tty, struct file *file, 
	n_tty_set_room(tty);

	up_read(&tty->termios_rwsem);



	mutex_unlock(&ldata->atomic_read_lock);

	remove_wait_queue(&tty->read_wait, &wait);



	if (!waitqueue_active(&tty->read_wait))

		ldata->minimum_to_wake = minimum;



	mutex_unlock(&ldata->atomic_read_lock);



	__set_current_state(TASK_RUNNING);

	if (b - buf)

		retval = b - buf;