serial: 8250_fintek: Fix potential NULL pointer dereference

Fix potential NULL pointer dereference on
'commit 4da22f1418cb ("serial: 8250_fintek: fix the mismatched IRQ mode")'

We try to fix IRQ mode mismatch issue and add the following code to detect IRQ Level or Edge mode.

struct irq_data *irq_data = irq_get_irq_data(uart->port.irq); bool level_mode = irqd_is_level_type(irq_data);

But *irq_data had not any check and pass to irqd_is_level_type(), it may lead to potential NULL pointer dereference.

Also modify detecting IRQ mode when fintek chip found.

Suggested-by Ricardo Ribalda Delgado <[email protected]>

Signed-off-by Ji-Ze Hong (Peter Hong) <[email protected]>

---
 drivers/tty/serial/8250/8250_fintek.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

drivers/tty/serial/8250/8250_fintek.c +11 -3

index 737b4b3..9119d0c 100644
@@ -212,8 +212,8 @@ int fintek_8250_probe(struct uart_8250_port *uart)
 {
        struct fintek_8250 *pdata;
        struct fintek_8250 probe_data;
-       struct irq_data *irq_data = irq_get_irq_data(uart->port.irq);
-       bool level_mode = irqd_is_level_type(irq_data);
+       struct irq_data *irq_data;
+       bool level_mode = false; /* Default to Edge/High */
 
        if (find_base_port(&probe_data, uart->port.iobase))
                return -ENODEV;

@@ -226,5 +226,14 @@ int fintek_8250_probe(struct uart_8250_port *uart)
        uart->port.rs485_config = fintek_8250_rs485_config;
        uart->port.private_data = pdata;
 
+       irq_data = irq_get_irq_data(uart->port.irq);
+       if (irq_data) {
+               level_mode = irqd_is_level_type(irq_data);
+       } else {
+               dev_warn(uart->port.dev,
+                        "%s: Can't get irq_data, set this port to Edge/High",
+                        __func__);
+       }
+
        return fintek_8250_set_irq_mode(pdata, level_mode);
 }
--

1.9.1