[PATCH v6 0/3] coresight: prevent deactivate active config while enabling the config

[Yeoreum Yun]

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.
cfs_csdev_enable_config

To address this,
  Patch #1 fix missing disable config when etm4 device is disabled via sysfs
  Patch #2 holding cscfg_csdev_lock while removing config from cscfg_csdsev_list
  Patch #3 add wrapper to prevent deactivation of config whlie enabling it

Patch History
==============
>From v5 to v6:
  - add fixes tag.
  - using guard for locking.
  - https://lore.kernel.org/all/20250513170622.3071637-1-yeoreum.yun@arm.com/

>From v4 to v5
  - separate patch set (from Leo Yan)
  - https://lore.kernel.org/all/20250324191740.64964-1-yeoreum.yun@arm.com/


Yeoreum Yun (3):
  coresight/etm4: fix missing disable active config
  coresight: holding cscfg_csdev_lock while removing cscfg from csdev
  coresight: prevent deactivate active config while enabling the config

 .../hwtracing/coresight/coresight-config.h    |  2 +-
 .../coresight/coresight-etm4x-core.c          |  3 ++
 .../hwtracing/coresight/coresight-syscfg.c    | 51 +++++++++++++------
 3 files changed, 40 insertions(+), 16 deletions(-)

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