tty: fix termios input-speed encoding

[ Upstream commit fada18c4 ]

Make sure to clear the CIBAUD bits before OR-ing the new mask when
encoding the termios input baud rate.

This could otherwise lead to an incorrect input rate being reported back
and incidentally set on subsequent termios updates.

Fixes: edc6afc5 ("[PATCH] tty: switch to ktermios and new framework")
Signed-off-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/tty_baudrate.c

@@ -172,6 +172,9 @@ void tty_termios_encode_baud_rate(struct ktermios *termios,
 		iclose = 0;
 #endif
 	termios->c_cflag &= ~CBAUD;
+#ifdef IBSHIFT
+	termios->c_cflag &= ~(CBAUD << IBSHIFT);
+#endif
 
 	/*
 	 *	Our goal is to find a close match to the standard baud rate