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

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
...@@ -1057,7 +1057,7 @@ int tty_perform_flush(struct tty_struct *tty, unsigned long arg) ...@@ -1057,7 +1057,7 @@ int tty_perform_flush(struct tty_struct *tty, unsigned long arg)
if (retval) if (retval)
return retval; return retval;
ld = tty_ldisc_ref(tty); ld = tty_ldisc_ref_wait(tty);
switch (arg) { switch (arg) {
case TCIFLUSH: case TCIFLUSH:
if (ld && ld->ops->flush_buffer) if (ld && ld->ops->flush_buffer)
......
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