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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org,
        Srinivas Kandagatla <srinivas.kandagatla@st.com>,
        =?UTF-8?q?Ilpo=20J=C3=A4rvinen?= <ilpo.jarvinen@linux.intel.com>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 4.19 210/287] serial: st-asc: Sanitize CSIZE and correct PARENB for CS7
Date:   Mon, 13 Jun 2022 12:10:34 +0200
Message-Id: <20220613094930.230209297@linuxfoundation.org>
In-Reply-To: <20220613094923.832156175@linuxfoundation.org>
References: <20220613094923.832156175@linuxfoundation.org>
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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 7971997cdead..ce35e3a131b1 100644
--- a/drivers/tty/serial/st-asc.c
+++ b/drivers/tty/serial/st-asc.c
@@ -540,10 +540,14 @@ 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