serial: sifive: Sanitize CSIZE and c_iflag

[ Upstream commit c069d27 ]

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.

Fixes: 45c054d (tty: serial: add driver for the SiFive UART)
Cc: Paul Walmsley <paul.walmsley@sifive.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Link: https://lore.kernel.org/r/20220519081808.3776-7-ilpo.jarvinen@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

drivers/tty/serial/sifive.c

@@ -667,12 +667,16 @@ 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;