From: Peter Hurley Date: Thu, 7 Nov 2013 19:01:57 +0000 (-0500) Subject: n_tty: Protect minimum_to_wake reset for concurrent readers X-Git-Tag: firefly_0821_release~176^2~4812^2~2 X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=aebf045382edb32bd763d8edea02a559e7dc41e9;p=firefly-linux-kernel-4.4.55.git 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: Peter Hurley Signed-off-by: Greg Kroah-Hartman --- diff --git a/drivers/tty/n_tty.c b/drivers/tty/n_tty.c index c222a561c5ac..0f74945af624 100644 --- a/drivers/tty/n_tty.c +++ b/drivers/tty/n_tty.c @@ -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;