From f743061a85f5e9989df22ccbf07c80c98fc90e08 Mon Sep 17 00:00:00 2001 From: Andy Shevchenko Date: Tue, 7 Jul 2020 00:49:03 +0300 Subject: [PATCH] serial: core: Initialise spin lock before use in uart_configure_port() 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 Reported-by: Lad Prabhakar Reported-by: Guenter Roeck Reported-by: Anatoly Pugachev Acked-by: Marc Zyngier Tested-by: Tony Lindgren Cc: Geert Uytterhoeven Signed-off-by: Andy Shevchenko Tested-by: Lad Prabhakar Link: https://lore.kernel.org/r/20200706214903.56148-1-andriy.shevchenko@linux.intel.com Signed-off-by: Greg Kroah-Hartman --- 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 abb102e..5f3daab 100644 --- a/drivers/tty/serial/serial_core.c +++ b/drivers/tty/serial/serial_core.c @@ -1914,6 +1914,12 @@ 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. @@ -1923,8 +1929,7 @@ 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) @@ -2371,6 +2376,13 @@ uart_configure_port(struct uart_driver *drv, struct uart_state *state, 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() * We probably don't need a spinlock around this, but -- 2.7.4