Re: [PATCH V2 1/2] tty: serial: qcom_geni_serial: Allocate port->rx_fifo buffer in probe

[Stephen Boyd <swboyd@xxxxxxxxxxxx>]

Quoting satya priya (2020-02-25 05:54:21)
> To fix the RX cancel command failure, rx_fifo buffer needs to be
> flushed in stop_rx() by calling handle_rx().
> 
> 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@xxxxxxxxxxxxxx>

Please give me reported-by credit.

Reported-by: Stephen Boyd <swboyd@xxxxxxxxxxxx>

> ---
>  drivers/tty/serial/qcom_geni_serial.c | 13 +++++++------
>  1 file changed, 7 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/tty/serial/qcom_geni_serial.c b/drivers/tty/serial/qcom_geni_serial.c
> index 191abb1..d2a909c 100644
> --- a/drivers/tty/serial/qcom_geni_serial.c
> +++ b/drivers/tty/serial/qcom_geni_serial.c
> @@ -858,12 +858,6 @@ 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;
> @@ -1274,6 +1268,13 @@ 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;
> +       }

Is there any reason the rx_fifo pointer is a u32 instead of a u8 or void
pointer? ioread32_rep() doesn't care what the pointer is and then we
have to cast it, so it seems like we should do something like below too.

-----8<-----

diff --git a/drivers/tty/serial/qcom_geni_serial.c b/drivers/tty/serial/qcom_geni_serial.c
index 191abb18fc2a..b4875dfef6aa 100644
--- a/drivers/tty/serial/qcom_geni_serial.c
+++ b/drivers/tty/serial/qcom_geni_serial.c
@@ -113,7 +113,7 @@ struct qcom_geni_serial_port {
 	unsigned int baud;
 	unsigned int tx_bytes_pw;
 	unsigned int rx_bytes_pw;
-	u32 *rx_fifo;
+	u8 *rx_fifo;
 	u32 loopback;
 	bool brk;
 
@@ -504,7 +504,6 @@ 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;
@@ -516,8 +515,7 @@ 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);