[PATCH 1/7] USB: serial: ftdi_sio: Fix divisor overflow

["Marek Behún" <kabel@kernel.org>]

From: Pali Rohár <pali@kernel.org>

Divisor in the register is a 17-bit wide number.
Therefore we need to clamp it on overflow.

Signed-off-by: Pali Rohár <pali@kernel.org>
Tested-by: Marek Behún <kabel@kernel.org>
---
 drivers/usb/serial/ftdi_sio.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/usb/serial/ftdi_sio.c b/drivers/usb/serial/ftdi_sio.c
index b440d338a895..ea40f367e70c 100644
--- a/drivers/usb/serial/ftdi_sio.c
+++ b/drivers/usb/serial/ftdi_sio.c
@@ -1157,6 +1157,8 @@ static unsigned short int ftdi_232am_baud_base_to_divisor(int baud, int base)
 	int divisor3 = DIV_ROUND_CLOSEST(base, 2 * baud);
 	if ((divisor3 & 0x7) == 7)
 		divisor3++; /* round x.7/8 up to x+1 */
+	if (divisor3 > GENMASK(16, 0))
+		divisor3 = GENMASK(16, 0);
 	divisor = divisor3 >> 3;
 	divisor3 &= 0x7;
 	if (divisor3 == 1)
@@ -1181,6 +1183,8 @@ static u32 ftdi_232bm_baud_base_to_divisor(int baud, int base)
 	u32 divisor;
 	/* divisor shifted 3 bits to the left */
 	int divisor3 = DIV_ROUND_CLOSEST(base, 2 * baud);
+	if (divisor3 > GENMASK(16, 0))
+		divisor3 = GENMASK(16, 0);
 	divisor = divisor3 >> 3;
 	divisor |= (u32)divfrac[divisor3 & 0x7] << 14;
 	/* Deal with special cases for highest baud rates. */
@@ -1204,6 +1208,8 @@ static u32 ftdi_2232h_baud_base_to_divisor(int baud, int base)
 
 	/* hi-speed baud rate is 10-bit sampling instead of 16-bit */
 	divisor3 = DIV_ROUND_CLOSEST(8 * base, 10 * baud);
+	if (divisor3 > GENMASK(16, 0))
+		divisor3 = GENMASK(16, 0);
 
 	divisor = divisor3 >> 3;
 	divisor |= (u32)divfrac[divisor3 & 0x7] << 14;
-- 
2.35.1