On Thu, Mar 17, 2022 at 4:06 AM Jiri Slaby <jirislaby@xxxxxxxxxx> wrote: > > On 16. 03. 22, 15:36, Wander Lairson Costa wrote: > > The serial driver set the value of uart_8250_port.fcr in the function > > serial8250_config_port, but only writes the value to the controller > > register later in the initalization code. > > > > That opens a small window in which is not safe to use the fifo for > > console write. > > > > Make sure the port is initialized correctly before reading the FCR > > cached value. > > > > Unfortunately, I lost track of who originally reported the issue. If > > s/he is reading this, please speak up so I can give you the due credit. > > > > Signed-off-by: Wander Lairson Costa <wander@xxxxxxxxxx> > > --- > > drivers/tty/serial/8250/8250_port.c | 1 + > > 1 file changed, 1 insertion(+) > > > > diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c > > index 4acf620be241..7e2227161555 100644 > > --- a/drivers/tty/serial/8250/8250_port.c > > +++ b/drivers/tty/serial/8250/8250_port.c > > @@ -3416,6 +3416,7 @@ void serial8250_console_write(struct uart_8250_port *up, const char *s, > > !(up->capabilities & UART_CAP_MINI) && > > up->tx_loadsz > 1 && > > (up->fcr & UART_FCR_ENABLE_FIFO) && > > + test_bit(TTY_PORT_INITIALIZED, &port->state->port.iflags) && > > Cannot be port->state be NULL sometimes here? > IIUC, state is assigned at early port registration in uart_add_one_port(), so this function wouldn't be called when state is NULL. But I think it causes no harm to add an extra check. Thanks! > > /* > > * After we put a data in the FIFO, the controller will send > > * it regardless of the CTS state. Therefore, only use fifo > > > -- > js > suse labs >
