[PATCH 4.14 155/218] serial: st-asc: Sanitize CSIZE and correct PARENB for CS7

Greg Kroah-Hartman
2022-06-13T11:02:58Z

From: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>

[ Upstream commit 52bb1cb7118564166b04d52387bd8403632f5190 ]

Only CS7 and CS8 seem supported but CSIZE is not sanitized from CS5 or
CS6 to CS8. In addition, ASC_CTL_MODE_7BIT_PAR suggests that CS7 has
to have parity, thus add PARENB.

Incorrect CSIZE 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().

Fixes: c4b058560762 (serial:st-asc: Add ST ASC driver.)
Cc: Srinivas Kandagatla <srinivas.kandagatla@st.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Link: https://lore.kernel.org/r/20220519081808.3776-8-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/st-asc.c | 4 ++++
1 file changed, 4 insertions(+)

diff --git a/drivers/tty/serial/st-asc.c b/drivers/tty/serial/st-asc.c
index b313a792b149..44d52c087c56 100644
--- a/drivers/tty/serial/st-asc.c
+++ b/drivers/tty/serial/st-asc.c
@@ -545,10 +545,14 @@ static void asc_set_termios(struct uart_port *port, struct ktermios *termios,
/* set character length */
if ((cflag & CSIZE) == CS7) {
ctrl_val |= ASC_CTL_MODE_7BIT_PAR;
+ cflag |= PARENB;
} else {
ctrl_val |= (cflag & PARENB) ? ASC_CTL_MODE_8BIT_PAR :
ASC_CTL_MODE_8BIT;
+ cflag &= ~CSIZE;
+ cflag |= CS8;
}
+ termios->c_cflag = cflag;

/* set stop bit */
ctrl_val |= (cflag & CSTOPB) ? ASC_CTL_STOP_2BIT : ASC_CTL_STOP_1BIT;
--
2.35.1