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.
