From: Johan Hovold johan@kernel.org
commit 0c5aae59270fb1f827acce182786094c9ccf598e upstream.
The serdev tty-port controller driver should reset the tty-port client operations also on deregistration to avoid a NULL-pointer dereference in case the port is later re-registered as a normal tty device.
Note that this can only happen with tty drivers such as 8250 which have statically allocated port structures that can end up being reused and where a later registration would not register a serdev controller (e.g. due to registration errors or if the devicetree has been changed in between).
Specifically, this can be an issue for any statically defined ports that would be registered by 8250 core when an 8250 driver is being unbound.
Fixes: bed35c6dfa6a ("serdev: add a tty port controller driver") Cc: stable stable@vger.kernel.org # 4.11 Reported-by: Loic Poulain loic.poulain@linaro.org Signed-off-by: Johan Hovold johan@kernel.org Link: https://lore.kernel.org/r/20200210145730.22762-1-johan@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- drivers/tty/serdev/serdev-ttyport.c | 6 ++---- drivers/tty/tty_port.c | 5 +++-- include/linux/tty.h | 2 ++ 3 files changed, 7 insertions(+), 6 deletions(-)
--- a/drivers/tty/serdev/serdev-ttyport.c +++ b/drivers/tty/serdev/serdev-ttyport.c @@ -238,7 +238,6 @@ struct device *serdev_tty_port_register( struct device *parent, struct tty_driver *drv, int idx) { - const struct tty_port_client_operations *old_ops; struct serdev_controller *ctrl; struct serport *serport; int ret; @@ -257,7 +256,6 @@ struct device *serdev_tty_port_register(
ctrl->ops = &ctrl_ops;
- old_ops = port->client_ops; port->client_ops = &client_ops; port->client_data = ctrl;
@@ -270,7 +268,7 @@ struct device *serdev_tty_port_register(
err_reset_data: port->client_data = NULL; - port->client_ops = old_ops; + port->client_ops = &tty_port_default_client_ops; serdev_controller_put(ctrl);
return ERR_PTR(ret); @@ -285,8 +283,8 @@ int serdev_tty_port_unregister(struct tt return -ENODEV;
serdev_controller_remove(ctrl); - port->client_ops = NULL; port->client_data = NULL; + port->client_ops = &tty_port_default_client_ops; serdev_controller_put(ctrl);
return 0; --- a/drivers/tty/tty_port.c +++ b/drivers/tty/tty_port.c @@ -51,10 +51,11 @@ static void tty_port_default_wakeup(stru } }
-static const struct tty_port_client_operations default_client_ops = { +const struct tty_port_client_operations tty_port_default_client_ops = { .receive_buf = tty_port_default_receive_buf, .write_wakeup = tty_port_default_wakeup, }; +EXPORT_SYMBOL_GPL(tty_port_default_client_ops);
void tty_port_init(struct tty_port *port) { @@ -67,7 +68,7 @@ void tty_port_init(struct tty_port *port spin_lock_init(&port->lock); port->close_delay = (50 * HZ) / 100; port->closing_wait = (3000 * HZ) / 100; - port->client_ops = &default_client_ops; + port->client_ops = &tty_port_default_client_ops; kref_init(&port->kref); } EXPORT_SYMBOL(tty_port_init); --- a/include/linux/tty.h +++ b/include/linux/tty.h @@ -224,6 +224,8 @@ struct tty_port_client_operations { void (*write_wakeup)(struct tty_port *port); };
+extern const struct tty_port_client_operations tty_port_default_client_ops; + struct tty_port { struct tty_bufhead buf; /* Locked internally */ struct tty_struct *tty; /* Back pointer */