Commit c0253eec authored by Alan Cox's avatar Alan Cox Committed by Linus Torvalds
Browse files

tty: Fix race in the flush for some ldiscs 



If you issue an ioctl to flush a tty as the line discipline is changing or
otherwise unplugged you can get a crash. The bug is very old but the rest
of the BKL lock dropping and some very "good" luck on Ingo's part caught
an example.

Use the correct ldisc_ref form so that we wait for the ldisc change to
complete and then flush

Signed-off-by: default avatarAlan Cox <alan@redhat.com>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 5393f780

drivers/char/tty_ioctl.c

+1 −1
Original line number Diff line number Diff line
@@ -1057,7 +1057,7 @@ int tty_perform_flush(struct tty_struct *tty, unsigned long arg) 
	if (retval)

		return retval;



	ld = tty_ldisc_ref(tty);

	ld = tty_ldisc_ref_wait(tty);

	switch (arg) {

	case TCIFLUSH:

		if (ld && ld->ops->flush_buffer)