Thread (24 messages) 24 messages, 3 authors, 2014-08-22

Re: [PATCH 1/3] tty: omap-serial: prevent division by zero

From: Frans Klaver <hidden>
Date: 2014-07-29 15:00:21
Also in: linux-devicetree, lkml

Sorry, missed some CC's in git send-email.

On Tue, Jul 29, 2014 at 04:52:55PM +0200, Frans Klaver wrote:
quoted hunk ↗ jump to hunk
If the chosen baud rate is large enough (e.g. 3.5 megabaud), the
calculated n13 and n16 values in serial_omap_baud_is_mode16 may become
0. This causes a division by zero when calculating the difference
between calculated and desired baud rates. To prevent this, cap n13 and
n16 on 1.

Signed-off-by: Frans Klaver <redacted>
---
 drivers/tty/serial/omap-serial.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)
diff --git a/drivers/tty/serial/omap-serial.c b/drivers/tty/serial/omap-serial.c
index d017cec..e454b7c 100644
--- a/drivers/tty/serial/omap-serial.c
+++ b/drivers/tty/serial/omap-serial.c
@@ -254,8 +254,16 @@ serial_omap_baud_is_mode16(struct uart_port *port, unsigned int baud)
 {
 	unsigned int n13 = port->uartclk / (13 * baud);
 	unsigned int n16 = port->uartclk / (16 * baud);
-	int baudAbsDiff13 = baud - (port->uartclk / (13 * n13));
-	int baudAbsDiff16 = baud - (port->uartclk / (16 * n16));
+	int baudAbsDiff13;
+	int baudAbsDiff16;
+
+	if (n13 == 0)
+		n13 = 1;
+	if (n16 == 0)
+		n16 = 1;
+
+	baudAbsDiff13 = baud - (port->uartclk / (13 * n13));
+	baudAbsDiff16 = baud - (port->uartclk / (16 * n16));
 	if (baudAbsDiff13 < 0)
 		baudAbsDiff13 = -baudAbsDiff13;
 	if (baudAbsDiff16 < 0)
-- 
1.9.3
--
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