On Tue, Apr 16, 2024 at 11:00:25AM +0800, sicong wrote:

greybus/interface.c: use-after-free bug in gb_interface_release due to race condition.

In gb_interface_create, &intf->mode_switch_completion is bound with gb_interface_mode_switch_work. Then it will be started by gb_interface_request_mode_switch. Here is the code. if (!queue_work(system_long_wq, &intf->mode_switch_work)) { ... }

If we call gb_interface_release to make cleanup, there may be an unfinished work. This function will call kfree to free the object "intf". However, if gb_interface_mode_switch_work is scheduled to run after kfree, it may cause use-after-free error as gb_interface_mode_switch_work will use the object "intf". The possible execution flow that may lead to the issue is as follows:

CPU0 CPU1

                        |   gb_interface_create
                        |   gb_interface_request_mode_switch

gb_interface_release | kfree(intf) (free) | | gb_interface_mode_switch_work | mutex_lock(&intf->mutex) (use)

This bug may be fixed by adding the following code before kfree. cancel_work_sync(&intf->mode_switch_work);

Wonderful, please submit a patch with this information and we will be glad to review it.

thanks,

greg k-h