[PATCH 3/4] tty/serial: at91: prevent null dereference in tasklet function

[Nicolas Ferre]

From: Marek Roszko <mark.roszko at gmail.com>

Something asks a tasklet to be scheduled when the uart port is closed.
Need to supress the kernel panic for now by checking if the port is NULL or
not.

Signed-off-by: Marek Roszko <mark.roszko at gmail.com>
Acked-by: Leilei Zhao <leilei.zhao at atmel.com>
Cc: <stable at vger.kernel.org> # v3.12
Signed-off-by: Nicolas Ferre <nicolas.ferre at atmel.com>
---
 drivers/tty/serial/atmel_serial.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/tty/serial/atmel_serial.c b/drivers/tty/serial/atmel_serial.c
index c421d11b3d4c..6e68486c83cb 100644
--- a/drivers/tty/serial/atmel_serial.c
+++ b/drivers/tty/serial/atmel_serial.c
@@ -1360,6 +1360,10 @@ static void atmel_tasklet_func(unsigned long data)
 	unsigned int status;
 	unsigned int status_change;
 
+	if(!port->state || !port->state->port.tty)
+		/* uart has been closed */
+		return;
+
 	/* The interrupt handler does not take the lock */
 	spin_lock(&port->lock);
 
-- 
1.8.2.2