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USB: serial: f81534: fix division by zero on line-speed change

PATCH In review Johan Hovold 2 participants 2 messages Nov 29, 2022 – Nov 30, 2022

Subsystems (3)
Stable branch USB USB serial
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Johan Hovold

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#0 lore raw

PATCH 1/1 USB: serial: f81534: fix division by zero on line-speed change

The driver leaves the line speed unchanged in case a requested speed is not supported. Make sure to handle the case where the current speed is B0 (hangup) without dividing by zero when determining the clock source.

Fixes 3aacac02f385 ("USB: serial: f81534: add high baud rate support")
Cc [email protected] # 4.16
Cc Ji-Ze Hong (Peter Hong) <[email protected]>
Signed-off-by Johan Hovold <[email protected]>
---
 drivers/usb/serial/f81534.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)
drivers/usb/serial/f81534.c +7 -5
index ddfcd72eb0ae..4083ae961be4 100644
@@ -536,9 +536,6 @@ static int f81534_submit_writer(struct usb_serial_port *port, gfp_t mem_flags)
 
 static u32 f81534_calc_baud_divisor(u32 baudrate, u32 clockrate)
 {
-	if (!baudrate)
-		return 0;
-
 	/* Round to nearest divisor */
 	return DIV_ROUND_CLOSEST(clockrate, baudrate);
 }

@@ -568,9 +565,14 @@ static int f81534_set_port_config(struct usb_serial_port *port,
 	u32 baud_list[] = {baudrate, old_baudrate, F81534_DEFAULT_BAUD_RATE};
 
 	for (i = 0; i < ARRAY_SIZE(baud_list); ++i) {
-		idx = f81534_find_clk(baud_list[i]);
+		baudrate = baud_list[i];
+		if (baudrate == 0) {
+			tty_encode_baud_rate(tty, 0, 0);
+			return 0;
+		}
+
+		idx = f81534_find_clk(baudrate);
 		if (idx >= 0) {
-			baudrate = baud_list[i];
 			tty_encode_baud_rate(tty, baudrate, baudrate);
 			break;
 		}
Signature · 1 line
2.37.4
maintainer Reviewed-by on v1 1/1
#1 lore raw
Quoted 8 lines · Johan Hovold

The driver leaves the line speed unchanged in case a requested speed is not supported. Make sure to handle the case where the current speed is B0 (hangup) without dividing by zero when determining the clock source.

Fixes 3aacac02f385 ("USB: serial: f81534: add high baud rate support")
Cc [email protected] # 4.16
Cc Ji-Ze Hong (Peter Hong) <[email protected]>
Signed-off-by Johan Hovold <[email protected]>
Reviewed-by Greg Kroah-Hartman <[email protected]>