4.14-stable review patch. If anyone has any objections, please let me know.
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From: Johan Hovold johan@kernel.org
commit eb281683621b71ab9710d9dccbbef0c2e1769c97 upstream.
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: cd6484e1830b ("serdev: Introduce new bus for serial attached devices") Signed-off-by: Johan Hovold johan@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- drivers/tty/serdev/serdev-ttyport.c | 13 ++++++++++++- 1 file changed, 12 insertions(+), 1 deletion(-)
--- a/drivers/tty/serdev/serdev-ttyport.c +++ b/drivers/tty/serdev/serdev-ttyport.c @@ -35,11 +35,22 @@ static int ttyport_receive_buf(struct tt { 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)