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serial: core: Prevent unsafe uart port access, part 3 

For tty operations which may expect uart port to have been removed
but still have other necessary work to accomplish, check for NULL
uart port; specifically uart_close(), uart_hangup() and sub-functions
(uart_shutdown() and uart_port_shutdown()).

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Peter Hurley 2016-04-09 18:56:35 -07:00 committed by Greg Kroah-Hartman
parent 9ed19428a5
commit af224ca2df
1 changed files with 20 additions and 10 deletions
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30
drivers/tty/serial/serial_core.c
View File

@ -257,6 +257,8 @@ static int uart_startup(struct tty_struct *tty, struct uart_state *state,
* This routine will shutdown a serial port; interrupts are disabled, and
* DTR is dropped if the hangup on close termio flag is on. Calls to
* uart_shutdown are serialised by the per-port semaphore.
*
* uport == NULL if uart_port has already been removed
*/
static void uart_shutdown(struct tty_struct *tty, struct uart_state *state)
{
@ -275,7 +277,7 @@ static void uart_shutdown(struct tty_struct *tty, struct uart_state *state)
/*
* Turn off DTR and RTS early.
*/
if (uart_console(uport) && tty)
if (uport && uart_console(uport) && tty)
uport->cons->cflag = tty->termios.c_cflag;
if (!tty || C_HUPCL(tty))
@ -1460,7 +1462,6 @@ out:
* Calls to uart_close() are serialised via the tty_lock in
* drivers/tty/tty_io.c:tty_release()
* drivers/tty/tty_io.c:do_tty_hangup()
* This runs from a workqueue and can sleep for a _short_ time only.
*/
static void uart_close(struct tty_struct *tty, struct file *filp)
{
@ -1479,18 +1480,21 @@ static void uart_close(struct tty_struct *tty, struct file *filp)
return;
}
uport = state->uart_port;
port = &state->port;
pr_debug("uart_close(%d) called\n", tty->index);
if (!port->count || tty_port_close_start(port, tty, filp) == 0)
if (tty_port_close_start(port, tty, filp) == 0)
return;
mutex_lock(&port->mutex);
uport = uart_port_check(state);
/*
* At this point, we stop accepting input. To do this, we
* disable the receive line status interrupts.
*/
if (tty_port_initialized(port)) {
if (tty_port_initialized(port) &&
!WARN(!uport, "detached port still initialized!\n")) {
spin_lock_irq(&uport->lock);
uport->ops->stop_rx(uport);
spin_unlock_irq(&uport->lock);
@ -1502,7 +1506,6 @@ static void uart_close(struct tty_struct *tty, struct file *filp)
uart_wait_until_sent(tty, uport->timeout);
}
mutex_lock(&port->mutex);
uart_shutdown(tty, state);
tty_port_tty_set(port, NULL);
@ -1513,7 +1516,7 @@ static void uart_close(struct tty_struct *tty, struct file *filp)
if (port->close_delay)
msleep_interruptible(jiffies_to_msecs(port->close_delay));
spin_lock_irq(&port->lock);
} else if (!uart_console(uport)) {
} else if (uport && !uart_console(uport)) {
spin_unlock_irq(&port->lock);
uart_change_pm(state, UART_PM_STATE_OFF);
spin_lock_irq(&port->lock);
@ -1600,11 +1603,15 @@ static void uart_hangup(struct tty_struct *tty)
{
struct uart_state *state = tty->driver_data;
struct tty_port *port = &state->port;
struct uart_port *uport;
unsigned long flags;
pr_debug("uart_hangup(%d)\n", tty->index);
mutex_lock(&port->mutex);
uport = uart_port_check(state);
WARN(!uport, "hangup of detached port!\n");
if (tty_port_active(port)) {
uart_flush_buffer(tty);
uart_shutdown(tty, state);
@ -1613,7 +1620,7 @@ static void uart_hangup(struct tty_struct *tty)
spin_unlock_irqrestore(&port->lock, flags);
tty_port_set_active(port, 0);
tty_port_tty_set(port, NULL);
if (!uart_console(state->uart_port))
if (uport && !uart_console(uport))
uart_change_pm(state, UART_PM_STATE_OFF);
wake_up_interruptible(&port->open_wait);
wake_up_interruptible(&port->delta_msr_wait);
@ -1621,6 +1628,7 @@ static void uart_hangup(struct tty_struct *tty)
mutex_unlock(&port->mutex);
}
/* uport == NULL if uart_port has already been removed */
static void uart_port_shutdown(struct tty_port *port)
{
struct uart_state *state = container_of(port, struct uart_state, port);
@ -1638,12 +1646,14 @@ static void uart_port_shutdown(struct tty_port *port)
/*
* Free the IRQ and disable the port.
*/
uport->ops->shutdown(uport);
if (uport)
uport->ops->shutdown(uport);
/*
* Ensure that the IRQ handler isn't running on another CPU.
*/
synchronize_irq(uport->irq);
if (uport)
synchronize_irq(uport->irq);
}
static int uart_carrier_raised(struct tty_port *port)