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Subject[PATCH v2 13/19] tty: Handle NULL tty->ldisc
Date
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>
---
drivers/tty/tty_ldisc.c | 16 ++++++++++++----
1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/drivers/tty/tty_ldisc.c b/drivers/tty/tty_ldisc.c
index 1c9ce25..5115230 100644
--- a/drivers/tty/tty_ldisc.c
+++ b/drivers/tty/tty_ldisc.c
@@ -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);
@@ -462,7 +463,7 @@ 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;
@@ -483,7 +484,7 @@ 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);
}

/**
@@ -546,6 +547,11 @@ 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;
@@ -661,7 +667,7 @@ 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) {
@@ -745,6 +751,8 @@ 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
*/
--
2.7.0
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