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