coresight: prevent deactivate active config while enabling the config

In the Linux kernel, the following vulnerability has been resolved:

coresight: prevent deactivate active config while enabling the config

While enable active config via cscfg_csdev_enable_active_config(),

active config could be deactivated via configfs' sysfs interface.

This could make UAF issue in below scenario:

CPU0 CPU1

(sysfs enable) load module

cscfg_load_config_sets()

activate config. // sysfs

(sys_active_cnt == 1)

...

cscfg_csdev_enable_active_config()

lock(csdev->cscfg_csdev_lock)

// here load config activate by CPU1

unlock(csdev->cscfg_csdev_lock)

deactivate config // sysfs

(sys_activec_cnt == 0)

cscfg_unload_config_sets()

unload module

// access to config_desc which freed

// while unloading module.

cscfg_csdev_enable_config

To address this, use cscfg_config_desc's active_cnt as a reference count

which will be holded when

- activate the config.

- enable the activated config.

and put the module reference when config_active_cnt == 0.