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Commit eb281683 authored by Johan Hovold's avatar Johan Hovold Committed by Greg Kroah-Hartman
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serdev: ttyport: add missing receive_buf sanity checks 



The receive_buf tty-port callback should return the number of bytes
accepted and must specifically never return a negative errno (or a value
larger than the buffer size) to the tty layer.

A serdev driver not providing a receive_buf callback would currently
cause the flush_to_ldisc() worker to spin in a tight loop when the tty
buffer pointers are incremented with -EINVAL (-22) after data has been
received.

A serdev driver occasionally returning a negative errno (or a too large
byte count) could cause information leaks or crashes when accessing
memory outside the tty buffers in consecutive callbacks.

Fixes: cd6484e1 ("serdev: Introduce new bus for serial attached devices")
Cc: stable <stable@vger.kernel.org>	# 4.11
Signed-off-by: default avatarJohan Hovold <johan@kernel.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 0ff3ab70

drivers/tty/serdev/serdev-ttyport.c

+12 −1
Original line number Diff line number Diff line
@@ -27,11 +27,22 @@ static int ttyport_receive_buf(struct tty_port *port, const unsigned char *cp, 
{

	struct serdev_controller *ctrl = port->client_data;

	struct serport *serport = serdev_controller_get_drvdata(ctrl);

	int ret;



	if (!test_bit(SERPORT_ACTIVE, &serport->flags))

		return 0;



	return serdev_controller_receive_buf(ctrl, cp, count);

	ret = serdev_controller_receive_buf(ctrl, cp, count);



	dev_WARN_ONCE(&ctrl->dev, ret < 0 || ret > count,

				"receive_buf returns %d (count = %zu)\n",

				ret, count);

	if (ret < 0)

		return 0;

	else if (ret > count)

		return count;



	return ret;

}



static void ttyport_write_wakeup(struct tty_port *port)