4.14-stable review patch. If anyone has any objections, please let me know. ------------------ From: Johan Hovold <johan@xxxxxxxxxx> [ Upstream commit fd00cf81a9a84776ba58e56bd042c726dcf75cf3 ] The receive_buf callback is supposed to return the number of bytes processed and should specifically not return a negative errno. Due to missing sanity checks in the serdev tty-port controller, a driver not providing a receive_buf callback could cause the flush_to_ldisc() worker to spin in a tight loop when the tty buffer pointers are incremented with -EINVAL (-22). The missing sanity checks have now been added to the tty-port controller, but let's fix up the serdev-controller helper as well. Signed-off-by: Johan Hovold <johan@xxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- include/linux/serdev.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/include/linux/serdev.h +++ b/include/linux/serdev.h @@ -184,7 +184,7 @@ static inline int serdev_controller_rece struct serdev_device *serdev = ctrl->serdev; if (!serdev || !serdev->ops->receive_buf) - return -EINVAL; + return 0; return serdev->ops->receive_buf(serdev, data, count); }