linux-kernel - [PATCH 6/9] serial: sifive: Sanitize CSIZE and c

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Date:   Tue, 17 May 2022 14:07:34 +0300
From:   Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
To:     linux-serial@...r.kernel.org, Greg KH <gregkh@...uxfoundation.org>,
        Jiri Slaby <jirislaby@...nel.org>,
        Palmer Dabbelt <palmer@...belt.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org
Cc:     Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
Subject: [PATCH 6/9] serial: sifive: Sanitize CSIZE and c_iflag

Only CS8 is supported but CSIZE was not sanitized to CS8.

Set CSIZE correctly so that userspace knows the effective value.
Incorrect CSIZE also results in miscalculation of the frame bits in
tty_get_char_size() or in its predecessor where the roughly the same
code is directly within uart_update_timeout().

Similarly, INPCK, PARMRK, and BRKINT are reported textually unsupported
but were not cleared in termios c_iflag which is the machine-readable
format.

Cc: Paul Walmsley <paul.walmsley@...ive.com>
Fixes: 45c054d0815b (tty: serial: add driver for the SiFive UART)
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
---
 drivers/tty/serial/sifive.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/tty/serial/sifive.c b/drivers/tty/serial/sifive.c
index f5ac14c384c4..c1c0fb9c1822 100644
--- a/drivers/tty/serial/sifive.c
+++ b/drivers/tty/serial/sifive.c
@@ -666,12 +666,16 @@ static void sifive_serial_set_termios(struct uart_port *port,
 	int rate;
 	char nstop;
 
-	if ((termios->c_cflag & CSIZE) != CS8)
+	if ((termios->c_cflag & CSIZE) != CS8) {
 		dev_err_once(ssp->port.dev, "only 8-bit words supported\n");
+		termios->c_cflag &= ~CSIZE;
+		termios->c_cflag |= CS8;
+	}
 	if (termios->c_iflag & (INPCK | PARMRK))
 		dev_err_once(ssp->port.dev, "parity checking not supported\n");
 	if (termios->c_iflag & BRKINT)
 		dev_err_once(ssp->port.dev, "BREAK detection not supported\n");
+	termios->c_iflag &= ~(INPCK|PARMRK|BRKINT);
 
 	/* Set number of stop bits */
 	nstop = (termios->c_cflag & CSTOPB) ? 2 : 1;
-- 
2.30.2