[PATCH V2] tty: serial: fsl_lpuart: fix the potential risk of division or modulo by zero

[Sherry Sun]

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@xxxxxxx>
---
V2: Amend commit message according to the review suggestions for better
understand the change. 
---
 drivers/tty/serial/fsl_lpuart.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/tty/serial/fsl_lpuart.c b/drivers/tty/serial/fsl_lpuart.c
index 794035041744..777d54b593f8 100644
--- 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);
 	/*
-- 
2.17.1