From c0253eec2a8e1140dd9672a1efe095cdcf5811d0 Mon Sep 17 00:00:00 2001
From: Alan Cox <alan@redhat.com>
Date: Thu, 15 Jan 2009 13:30:25 +0000
Subject: [PATCH] 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>
---
drivers/char/tty_ioctl.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/char/tty_ioctl.c b/drivers/char/tty_ioctl.c
index a408c8e487ec..6f4c7d0a53bf 100644
--- a/drivers/char/tty_ioctl.c
+++ b/drivers/char/tty_ioctl.c
@@ -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)
--
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