From: Andy Shevchenko andriy.shevchenko@linux.intel.com
[ Upstream commit f743061a85f5e9989df22ccbf07c80c98fc90e08 ]
The comment near to uart_port_spin_lock_init() says:
Ensure that the serial console lock is initialised early. If this port is a console, then the spinlock is already initialised.
and there is nothing about enabled or disabled consoles. The commit a3cb39d258ef ("serial: core: Allow detach and attach serial device for console") made a change, which follows the comment, and also to prevent reinitialisation of the lock in use, when user detaches and attaches back the same console device. But this change discovers another issue, that uart_add_one_port() tries to access a spin lock that now may be uninitialised. This happens when a driver expects the serial core to register a console on its behalf. In this case we must initialise a spin lock before use.
Fixes: a3cb39d258ef ("serial: core: Allow detach and attach serial device for console") Reported-by: Marc Zyngier maz@kernel.org Reported-by: Lad Prabhakar prabhakar.mahadev-lad.rj@bp.renesas.com Reported-by: Guenter Roeck linux@roeck-us.net Reported-by: Anatoly Pugachev matorola@gmail.com Acked-by: Marc Zyngier maz@kernel.org Tested-by: Tony Lindgren tony@atomide.com Cc: Geert Uytterhoeven geert@linux-m68k.org Signed-off-by: Andy Shevchenko andriy.shevchenko@linux.intel.com Tested-by: Lad Prabhakar prabhakar.mahadev-lad.rj@bp.renesas.com Link: https://lore.kernel.org/r/20200706214903.56148-1-andriy.shevchenko@linux.int... Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/tty/serial/serial_core.c | 16 ++++++++++++++-- 1 file changed, 14 insertions(+), 2 deletions(-)
diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c index 66a5e2faf57ea..ca5e6212bf1ce 100644 --- a/drivers/tty/serial/serial_core.c +++ b/drivers/tty/serial/serial_core.c @@ -1916,6 +1916,12 @@ static inline bool uart_console_enabled(struct uart_port *port) return uart_console(port) && (port->cons->flags & CON_ENABLED); }
+static void __uart_port_spin_lock_init(struct uart_port *port) +{ + spin_lock_init(&port->lock); + lockdep_set_class(&port->lock, &port_lock_key); +} + /* * Ensure that the serial console lock is initialised early. * If this port is a console, then the spinlock is already initialised. @@ -1925,8 +1931,7 @@ static inline void uart_port_spin_lock_init(struct uart_port *port) if (uart_console(port)) return;
- spin_lock_init(&port->lock); - lockdep_set_class(&port->lock, &port_lock_key); + __uart_port_spin_lock_init(port); }
#if defined(CONFIG_SERIAL_CORE_CONSOLE) || defined(CONFIG_CONSOLE_POLL) @@ -2372,6 +2377,13 @@ uart_configure_port(struct uart_driver *drv, struct uart_state *state, /* Power up port for set_mctrl() */ uart_change_pm(state, UART_PM_STATE_ON);
+ /* + * If this driver supports console, and it hasn't been + * successfully registered yet, initialise spin lock for it. + */ + if (port->cons && !(port->cons->flags & CON_ENABLED)) + __uart_port_spin_lock_init(port); + /* * Ensure that the modem control lines are de-activated. * keep the DTR setting that is set in uart_set_options()