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

On Wed, May 14, 2025 at 05:19:51PM +0100, Yeoreum Yun wrote:

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.

Fixes: f8cce2ff3c04 ("coresight: syscfg: Add API to activate and enable configurations") Signed-off-by: Yeoreum Yun yeoreum.yun@arm.com

Reviewed-by: Leo Yan leo.yan@arm.com

---

.../hwtracing/coresight/coresight-config.h | 2 +- .../hwtracing/coresight/coresight-syscfg.c | 49 +++++++++++++------ 2 files changed, 35 insertions(+), 16 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-config.h b/drivers/hwtracing/coresight/coresight-config.h index b9ebc9fcfb7f..90fd937d3bd8 100644 --- a/drivers/hwtracing/coresight/coresight-config.h +++ b/drivers/hwtracing/coresight/coresight-config.h @@ -228,7 +228,7 @@ struct cscfg_feature_csdev {

• @feats_csdev:references to the device features to enable.

*/ struct cscfg_config_csdev {

• const struct cscfg_config_desc *config_desc;

• struct cscfg_config_desc *config_desc; struct coresight_device *csdev; bool enabled; struct list_head node;

diff --git a/drivers/hwtracing/coresight/coresight-syscfg.c b/drivers/hwtracing/coresight/coresight-syscfg.c index 23017612f2ea..83dad24e0116 100644 --- a/drivers/hwtracing/coresight/coresight-syscfg.c +++ b/drivers/hwtracing/coresight/coresight-syscfg.c @@ -869,6 +869,25 @@ void cscfg_csdev_reset_feats(struct coresight_device *csdev) } EXPORT_SYMBOL_GPL(cscfg_csdev_reset_feats); +static bool cscfg_config_desc_get(struct cscfg_config_desc *config_desc) +{

• if (!atomic_fetch_inc(&config_desc->active_cnt)) {

• /* must ensure that config cannot be unloaded in use */
  

• if (unlikely(cscfg_owner_get(config_desc->load_owner))) {
  

• 	atomic_dec(&config_desc->active_cnt);
  

• 	return false;
  

• }
  

• }
• return true;

+}

+static void cscfg_config_desc_put(struct cscfg_config_desc *config_desc) +{

• if (!atomic_dec_return(&config_desc->active_cnt))

• cscfg_owner_put(config_desc->load_owner);
  

+}

/*

• This activate configuration for either perf or sysfs. Perf can have multiple
• active configs, selected per event, sysfs is limited to one.

@@ -892,22 +911,17 @@ static int _cscfg_activate_config(unsigned long cfg_hash) if (config_desc->available == false) return -EBUSY;

• 	/* must ensure that config cannot be unloaded in use */
  

• 	err = cscfg_owner_get(config_desc->load_owner);
  

• 	if (err)
  

• 	if (!cscfg_config_desc_get(config_desc)) {
  

• 		err = -EINVAL;
  	break;
  

• 	}
  

• /*
   * increment the global active count - control changes to
   * active configurations
   */
  atomic_inc(&cscfg_mgr->sys_active_cnt);
  

• 	/*
  

• 	 * mark the descriptor as active so enable config on a
  

• 	 * device instance will use it
  

• 	 */
  

• 	atomic_inc(&config_desc->active_cnt);
  

• err = 0;
  dev_dbg(cscfg_device(), "Activate config %s.\n", config_desc->name);
  break;
  

@@ -922,9 +936,8 @@ static void _cscfg_deactivate_config(unsigned long cfg_hash) list_for_each_entry(config_desc, &cscfg_mgr->config_desc_list, item) { if ((unsigned long)config_desc->event_ea->var == cfg_hash) {

• 	atomic_dec(&config_desc->active_cnt);
  atomic_dec(&cscfg_mgr->sys_active_cnt);
  

• 	cscfg_owner_put(config_desc->load_owner);
  

• 	cscfg_config_desc_put(config_desc);
  dev_dbg(cscfg_device(), "Deactivate config %s.\n", config_desc->name);
  break;
  

  }

@@ -1049,7 +1062,7 @@ int cscfg_csdev_enable_active_config(struct coresight_device *csdev, unsigned long cfg_hash, int preset) { struct cscfg_config_csdev *config_csdev_active = NULL, *config_csdev_item;

• const struct cscfg_config_desc *config_desc;

• struct cscfg_config_desc *config_desc; unsigned long flags; int err = 0;

@@ -1064,8 +1077,8 @@ int cscfg_csdev_enable_active_config(struct coresight_device *csdev, raw_spin_lock_irqsave(&csdev->cscfg_csdev_lock, flags); list_for_each_entry(config_csdev_item, &csdev->config_csdev_list, node) { config_desc = config_csdev_item->config_desc;

• if ((atomic_read(&config_desc->active_cnt)) &&
  

•     ((unsigned long)config_desc->event_ea->var == cfg_hash)) {
  

• if (((unsigned long)config_desc->event_ea->var == cfg_hash) &&
  

• 		cscfg_config_desc_get(config_desc)) {
  config_csdev_active = config_csdev_item;
  csdev->active_cscfg_ctxt = (void *)config_csdev_active;
  break;
  

@@ -1099,7 +1112,11 @@ int cscfg_csdev_enable_active_config(struct coresight_device *csdev, err = -EBUSY; raw_spin_unlock_irqrestore(&csdev->cscfg_csdev_lock, flags); }

• if (err)
  

• 	cscfg_config_desc_put(config_desc);
  

  }
• return err;

} EXPORT_SYMBOL_GPL(cscfg_csdev_enable_active_config); @@ -1138,8 +1155,10 @@ void cscfg_csdev_disable_active_config(struct coresight_device *csdev) raw_spin_unlock_irqrestore(&csdev->cscfg_csdev_lock, flags); /* true if there was an enabled active config */

• if (config_csdev)

• if (config_csdev) { cscfg_csdev_disable_config(config_csdev);

• cscfg_config_desc_put(config_csdev->config_desc);
  

• }

} EXPORT_SYMBOL_GPL(cscfg_csdev_disable_active_config); -- LEVI:{C3F47F37-75D8-414A-A8BA-3980EC8A46D7}