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tty: Handle NULL tty->ldisc

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In preparation of destroying line discipline on hangup, fix
ldisc core operations to properly handle when the tty's ldisc is
NULL.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Peter Hurley 2016-01-10 22:41:02 -08:00 committed by Greg Kroah-Hartman
parent e55afd11a4
commit a570a49abd
1 changed files with 12 additions and 4 deletions
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16
drivers/tty/tty_ldisc.c
View file

@ -269,7 +269,8 @@ const struct file_operations tty_ldiscs_proc_fops = {
struct tty_ldisc *tty_ldisc_ref_wait(struct tty_struct *tty)
{
ldsem_down_read(&tty->ldisc_sem, MAX_SCHEDULE_TIMEOUT);
WARN_ON(!tty->ldisc);
if (!tty->ldisc)
ldsem_up_read(&tty->ldisc_sem);
return tty->ldisc;
}
EXPORT_SYMBOL_GPL(tty_ldisc_ref_wait);
@ -460,7 +461,7 @@ static int tty_ldisc_open(struct tty_struct *tty, struct tty_ldisc *ld)
if (ret)
clear_bit(TTY_LDISC_OPEN, &tty->flags);
tty_ldisc_debug(tty, "%p: opened\n", tty->ldisc);
tty_ldisc_debug(tty, "%p: opened\n", ld);
return ret;
}
return 0;
@ -481,7 +482,7 @@ static void tty_ldisc_close(struct tty_struct *tty, struct tty_ldisc *ld)
clear_bit(TTY_LDISC_OPEN, &tty->flags);
if (ld->ops->close)
ld->ops->close(tty);
tty_ldisc_debug(tty, "%p: closed\n", tty->ldisc);
tty_ldisc_debug(tty, "%p: closed\n", ld);
}
/**
@ -544,6 +545,11 @@ int tty_set_ldisc(struct tty_struct *tty, int ldisc)
if (retval)
goto err;
if (!tty->ldisc) {
retval = -EIO;
goto out;
}
/* Check the no-op case */
if (tty->ldisc->ops->num == ldisc)
goto out;
@ -659,7 +665,7 @@ void tty_ldisc_hangup(struct tty_struct *tty)
int reset = tty->driver->flags & TTY_DRIVER_RESET_TERMIOS;
int err = 0;
tty_ldisc_debug(tty, "%p: closing\n", tty->ldisc);
tty_ldisc_debug(tty, "%p: hangup\n", tty->ldisc);
ld = tty_ldisc_ref(tty);
if (ld != NULL) {
@ -743,6 +749,8 @@ int tty_ldisc_setup(struct tty_struct *tty, struct tty_struct *o_tty)
static void tty_ldisc_kill(struct tty_struct *tty)
{
if (!tty->ldisc)
return;
/*
* Now kill off the ldisc
*/