From 2ea2e019c190ee3973ef7bcaf829d8762e56e635 Mon Sep 17 00:00:00 2001

From: Geert Uytterhoeven <geert+renesas@glider.be>

Date: Mon, 10 May 2021 14:07:55 +0200

Subject: [PATCH] serial: sh-sci: Fix off-by-one error in FIFO threshold register setting

Git-commit: 2ea2e019c190ee3973ef7bcaf829d8762e56e635

Patch-mainline: v5.13-rc4

References: git-fixes

The Receive FIFO Data Count Trigger field (RTRG[6:0]) in the Receive

FIFO Data Count Trigger Register (HSRTRGR) of HSCIF can only hold values

ranging from 0-127.  As the FIFO size is equal to 128 on HSCIF, the user

can write an out-of-range value, touching reserved bits.

Fix this by limiting the trigger value to the FIFO size minus one.

Reverse the order of the checks, to avoid rx_trig becoming zero if the

FIFO size is one.

Note that this change has no impact on other SCIF variants, as their

maximum supported trigger value is lower than the FIFO size anyway, and

the code below takes care of enforcing these limits.

Fixes: a380ed461f66d1b8 ("serial: sh-sci: implement FIFO threshold register setting")

Reported-by: Linh Phung <linh.phung.jy@renesas.com>

Reviewed-by: Wolfram Sang <wsa+renesas@sang-engineering.com>

Reviewed-by: Ulrich Hecht <uli+renesas@fpond.eu>

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>

Cc: stable <stable@vger.kernel.org>

Link: https://lore.kernel.org/r/5eff320aef92ffb33d00e57979fd3603bbb4a70f.1620648218.git.geert+renesas@glider.be

Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Acked-by: Takashi Iwai <tiwai@suse.de>

---

 drivers/tty/serial/sh-sci.c | 4 ++--

 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/tty/serial/sh-sci.c b/drivers/tty/serial/sh-sci.c

index ef37fdf37612..4baf1316ea72 100644

--- a/drivers/tty/serial/sh-sci.c

+++ b/drivers/tty/serial/sh-sci.c

@@ -1023,10 +1023,10 @@ static int scif_set_rtrg(struct uart_port *port, int rx_trig)

 {

 	unsigned int bits;

+	if (rx_trig >= port->fifosize)

+		rx_trig = port->fifosize - 1;

 	if (rx_trig < 1)

 		rx_trig = 1;

-	if (rx_trig >= port->fifosize)

-		rx_trig = port->fifosize;

 	/* HSCIF can be set to an arbitrary level. */

 	if (sci_getreg(port, HSRTRGR)->size) {

-- 

2.26.2