tty: serial: qcom_geni_serial: Allocate port->rx_fifo buffer in probe

To fix the RX cancel command failure, rx_fifo buffer needs to be
flushed in stop_rx() by calling handle_rx().In handle_rx() the data
in rx_fifo buffer is read and then dropped, not sent to upper layers.

If set_termios is called before startup, by this time memory is not
allocated to port->rx_fifo buffer, which leads to a NULL pointer
dereference.

To avoid this NULL pointer dereference allocate memory to port->rx_fifo
in probe itself.

Signed-off-by: satya priya <skakit@codeaurora.org>
Reported-by: Stephen Boyd <swboyd@chromium.org>
Link: https://lore.kernel.org/r/1583477228-32231-2-git-send-email-skakit@codeaurora.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/qcom_geni_serial.c

@@ -120,7 +120,7 @@ struct qcom_geni_serial_port {
 	unsigned int baud;
 	unsigned int tx_bytes_pw;
 	unsigned int rx_bytes_pw;
-	u32 *rx_fifo;
+	void *rx_fifo;
 	u32 loopback;
 	bool brk;
 
@@ -514,7 +514,6 @@ static int handle_rx_console(struct uart_port *uport, u32 bytes, bool drop)
 
 static int handle_rx_uart(struct uart_port *uport, u32 bytes, bool drop)
 {
-	unsigned char *buf;
 	struct tty_port *tport;
 	struct qcom_geni_serial_port *port = to_dev_port(uport, uport);
 	u32 num_bytes_pw = port->tx_fifo_width / BITS_PER_BYTE;
@@ -526,8 +525,7 @@ static int handle_rx_uart(struct uart_port *uport, u32 bytes, bool drop)
 	if (drop)
 		return 0;
 
-	buf = (unsigned char *)port->rx_fifo;
-	ret = tty_insert_flip_string(tport, buf, bytes);
+	ret = tty_insert_flip_string(tport, port->rx_fifo, bytes);
 	if (ret != bytes) {
 		dev_err(uport->dev, "%s:Unable to push data ret %d_bytes %d\n",
 				__func__, ret, bytes);
@@ -892,12 +890,6 @@ static int qcom_geni_serial_port_setup(struct uart_port *uport)
 						false, false, true);
 	geni_se_init(&port->se, UART_RX_WM, port->rx_fifo_depth - 2);
 	geni_se_select_mode(&port->se, GENI_SE_FIFO);
-	if (!uart_console(uport)) {
-		port->rx_fifo = devm_kcalloc(uport->dev,
-			port->rx_fifo_depth, sizeof(u32), GFP_KERNEL);
-		if (!port->rx_fifo)
-			return -ENOMEM;
-	}
 	port->setup = true;
 
 	return 0;
@@ -1308,6 +1300,13 @@ static int qcom_geni_serial_probe(struct platform_device *pdev)
 	port->rx_fifo_depth = DEF_FIFO_DEPTH_WORDS;
 	port->tx_fifo_width = DEF_FIFO_WIDTH_BITS;
 
+	if (!console) {
+		port->rx_fifo = devm_kcalloc(uport->dev,
+			port->rx_fifo_depth, sizeof(u32), GFP_KERNEL);
+		if (!port->rx_fifo)
+			return -ENOMEM;
+	}
+
 	port->name = devm_kasprintf(uport->dev, GFP_KERNEL,
 			"qcom_geni_serial_%s%d",
 			uart_console(uport) ? "console" : "uart", uport->line);