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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: Alan Cox <alan@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Alan Cox 2009-01-15 13:30:25 +00:00 committed by Linus Torvalds
parent 5393f78027
commit c0253eec2a
1 changed files with 1 additions and 1 deletions
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2
drivers/char/tty_ioctl.c
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@ -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)