tty: serial: fsl_lpuart: fix the potential risk of division or modulo by zero

We should be very careful about the register values that will be used
for division or modulo operations, althrough the possibility that the
UARTBAUD register value is zero is very low, but we had better to deal
with the "bad data" of hardware in advance to avoid division or modulo
by zero leading to undefined kernel behavior.

Signed-off-by: Sherry Sun <sherry.sun@nxp.com>
Link: https://lore.kernel.org/r/20210427021226.27468-1-sherry.sun@nxp.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/serial/fsl_lpuart.c b/drivers/tty/serial/fsl_lpuart.c
index 794035041744f9572ddef61f7ff9dbbda1d33cbb..777d54b593f8836c521d923c731124e8d8a17491 100644 (file)
--- a/drivers/tty/serial/fsl_lpuart.c
+++ b/drivers/tty/serial/fsl_lpuart.c
@@ -2414,6 +2414,9 @@ lpuart32_console_get_options(struct lpuart_port *sport, int *baud,
 
        bd = lpuart32_read(&sport->port, UARTBAUD);
        bd &= UARTBAUD_SBR_MASK;
+       if (!bd)
+               return;
+
        sbr = bd;
        uartclk = lpuart_get_baud_clk_rate(sport);
        /*