Commit 408c97c4 authored by Yeoreum Yun's avatar Yeoreum Yun Committed by Suzuki K Poulose
Browse files

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.

Fixes: f8cce2ff ("coresight: syscfg: Add API to activate and enable configurations")
Suggested-by: default avatarSuzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: default avatarYeoreum Yun <yeoreum.yun@arm.com>
Reviewed-by: default avatarLeo Yan <leo.yan@arm.com>
Signed-off-by: default avatarSuzuki K Poulose <suzuki.poulose@arm.com>
Link: https://lore.kernel.org/r/20250514161951.3427590-4-yeoreum.yun@arm.com
parent 53b9e265

drivers/hwtracing/coresight/coresight-config.h

+1 −1
Original line number Diff line number Diff line
@@ -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;

drivers/hwtracing/coresight/coresight-syscfg.c

+34 −15
Original line number Diff line number Diff line
@@ -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);