nvmet: Fix use-after-free bug when a port is removed

When a port is removed through configfs, any connected controllers
are still active and can still send commands. This causes a
use-after-free bug which is detected by KASAN for any admin command
that dereferences req->port (like in nvmet_execute_identify_ctrl).

To fix this, disconnect all active controllers when a subsystem is
removed from a port. This ensures there are no active controllers
when the port is eventually removed.

Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Reviewed-by: Max Gurtovoy <maxg@mellanox.com>
Reviewed-by : Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
Signed-off-by: Sagi Grimberg <sagi@grimberg.me>

drivers/nvme/target/configfs.c

@@ -675,6 +675,7 @@ static void nvmet_port_subsys_drop_link(struct config_item *parent,
 
 found:
 	list_del(&p->entry);
+	nvmet_port_del_ctrls(port, subsys);
 	nvmet_port_disc_changed(port, subsys);
 
 	if (list_empty(&port->subsystems))

drivers/nvme/target/core.c

@@ -280,6 +280,18 @@ void nvmet_unregister_transport(const struct nvmet_fabrics_ops *ops)
 }
 EXPORT_SYMBOL_GPL(nvmet_unregister_transport);
 
+void nvmet_port_del_ctrls(struct nvmet_port *port, struct nvmet_subsys *subsys)
+{
+	struct nvmet_ctrl *ctrl;
+
+	mutex_lock(&subsys->lock);
+	list_for_each_entry(ctrl, &subsys->ctrls, subsys_entry) {
+		if (ctrl->port == port)
+			ctrl->ops->delete_ctrl(ctrl);
+	}
+	mutex_unlock(&subsys->lock);
+}
+
 int nvmet_enable_port(struct nvmet_port *port)
 {
 	const struct nvmet_fabrics_ops *ops;

drivers/nvme/target/nvmet.h

@@ -418,6 +418,9 @@ void nvmet_port_send_ana_event(struct nvmet_port *port);
 int nvmet_register_transport(const struct nvmet_fabrics_ops *ops);
 void nvmet_unregister_transport(const struct nvmet_fabrics_ops *ops);
 
+void nvmet_port_del_ctrls(struct nvmet_port *port,
+			  struct nvmet_subsys *subsys);
+
 int nvmet_enable_port(struct nvmet_port *port);
 void nvmet_disable_port(struct nvmet_port *port);