[PATCH tty v1 7/8] serial: 8250: lock port for UART_IER access in omap8250_irq()

John Ogness
2023-05-25T09:35:22Z

omap8250_irq() accesses UART_IER. This register is modified twice
by each console write (serial8250_console_write()) under the port
lock. omap8250_irq() must also take the port lock to guanentee
synchronized access to UART_IER.

Since the port lock is already being taken for the stop_rx() callback
and since it is safe to call cancel_delayed_work() while holding the
port lock, simply extend the port lock region to include UART_IER
access.

Fixes: 1fe0e1fa3209 ("serial: 8250_omap: Handle optional overrun-throttle-ms property")
Signed-off-by: John Ogness <john.ogness@linutronix.de>
---
drivers/tty/serial/8250/8250_omap.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/tty/serial/8250/8250_omap.c b/drivers/tty/serial/8250/8250_omap.c
index 34939462fd69..3225c95fde1d 100644
--- a/drivers/tty/serial/8250/8250_omap.c
+++ b/drivers/tty/serial/8250/8250_omap.c
@@ -659,17 +659,18 @@ static irqreturn_t omap8250_irq(int irq, void *dev_id)
if ((lsr & UART_LSR_OE) && up->overrun_backoff_time_ms > 0) {
unsigned long delay;

+ /* Synchronize UART_IER access against the console. */
+ spin_lock(&port->lock);
up->ier = port->serial_in(port, UART_IER);
if (up->ier & (UART_IER_RLSI | UART_IER_RDI)) {
- spin_lock(&port->lock);
port->ops->stop_rx(port);
- spin_unlock(&port->lock);
} else {
/* Keep restarting the timer until
* the input overrun subsides.
*/
cancel_delayed_work(&up->overrun_backoff);
}
+ spin_unlock(&port->lock);

delay = msecs_to_jiffies(up->overrun_backoff_time_ms);
schedule_delayed_work(&up->overrun_backoff, delay);
--
2.30.2