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serial_core: Fix race in uart_handle_dcd_change 

If a serial driver is called post hangup with a second DCD event then we
will attempt to get the ldisc of NULL. Check we have a tty before trying to
do anything with it.

This is still only safe within the uart layer if the caller holds the
relevant uart locks. We could do with a version where the tty is passed for
more general use.

Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
hifive-unleashed-5.1
Alan Cox 2012-09-19 15:35:46 +01:00 committed by Greg Kroah-Hartman
parent 84c3b84860
commit 43eca0aef7
1 changed files with 7 additions and 4 deletions
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11
drivers/tty/serial/serial_core.c
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@ -2501,9 +2501,12 @@ void uart_handle_dcd_change(struct uart_port *uport, unsigned int status)
{
struct uart_state *state = uport->state;
struct tty_port *port = &state->port;
struct tty_ldisc *ld = tty_ldisc_ref(port->tty);
struct tty_ldisc *ld = NULL;
struct pps_event_time ts;
struct tty_struct *tty = port->tty;
if (tty)
ld = tty_ldisc_ref(tty);
if (ld && ld->ops->dcd_change)
pps_get_ts(&ts);
@ -2516,12 +2519,12 @@ void uart_handle_dcd_change(struct uart_port *uport, unsigned int status)
if (port->flags & ASYNC_CHECK_CD) {
if (status)
wake_up_interruptible(&port->open_wait);
else if (port->tty)
tty_hangup(port->tty);
else if (tty)
tty_hangup(tty);
}
if (ld && ld->ops->dcd_change)
ld->ops->dcd_change(port->tty, status, &ts);
ld->ops->dcd_change(tty, status, &ts);
if (ld)
tty_ldisc_deref(ld);
}