Re: [PATCH v3 1/1] coresight: prevent deactivate active config while enabling the config
Hi,
On Thu, 9 Jan 2025 at 17:20, Yeoreum Yun yeoreum.yun@arm.com 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. cfs_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.
Signed-off-by: Yeoreum Yun yeoreum.yun@arm.com
from v2 to v3: - add cscfg_config_desc_get()/put() (from Suzuki). - remove sys_enable_cnt.
from v1 to v2: - modify commit message.
.../hwtracing/coresight/coresight-config.h | 2 +- .../coresight/coresight-etm4x-core.c | 3 + .../hwtracing/coresight/coresight-syscfg.c | 55 ++++++++++++++----- 3 files changed, 44 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-etm4x-core.c b/drivers/hwtracing/coresight/coresight-etm4x-core.c index 86893115df17..6218ef40acbc 100644 --- a/drivers/hwtracing/coresight/coresight-etm4x-core.c +++ b/drivers/hwtracing/coresight/coresight-etm4x-core.c @@ -986,6 +986,9 @@ static void etm4_disable_sysfs(struct coresight_device *csdev) smp_call_function_single(drvdata->cpu, etm4_disable_hw, drvdata, 1);
raw_spin_unlock(&drvdata->spinlock);
cscfg_csdev_disable_active_config(csdev);cpus_read_unlock(); /*diff --git a/drivers/hwtracing/coresight/coresight-syscfg.c b/drivers/hwtracing/coresight/coresight-syscfg.c index a70c1454b410..8766f72db33e 100644 --- a/drivers/hwtracing/coresight/coresight-syscfg.c +++ b/drivers/hwtracing/coresight/coresight-syscfg.c @@ -391,14 +391,17 @@ static void cscfg_owner_put(struct cscfg_load_owner_info *owner_info) static void cscfg_remove_owned_csdev_configs(struct coresight_device *csdev, void *load_owner) { struct cscfg_config_csdev *config_csdev, *tmp;
unsigned long flags; if (list_empty(&csdev->config_csdev_list)) return;raw_spin_lock_irqsave(&csdev->cscfg_csdev_lock, flags); list_for_each_entry_safe(config_csdev, tmp, &csdev->config_csdev_list, node) { if (config_csdev->config_desc->load_owner == load_owner) list_del(&config_csdev->node); }raw_spin_unlock_irqrestore(&csdev->cscfg_csdev_lock, flags);}
static void cscfg_remove_owned_csdev_features(struct coresight_device *csdev, void *load_owner) @@ -867,6 +870,28 @@ 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, bool enable) +{
if (enable)return atomic_inc_not_zero(&config_desc->active_cnt);
Not sure why we have an "enable" parameter here - it completely changes the meaning of the function - with no comment at the start.
From where it is called it makes figuring out the logic confusing.
Just keep the "get" functionality and drop the parameter & the nz check.
/* when activate config *//* must ensure that config cannot be unloaded in use */if (cscfg_owner_get(config_desc->load_owner))return false;atomic_inc(&config_desc->active_cnt);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.
@@ -890,22 +915,17 @@ 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, false)) {
Drop the false parameter here.
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;@@ -920,9 +940,8 @@ 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; }@@ -1047,7 +1066,7 @@ 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;@@ -1062,8 +1081,8 @@ 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, true)) {
This obfuscates the logic of the comparisons without good reason. With the true parameter, the function does no "get" operation but just replicates the logic being replaced - checking the active_cnt is non-zero.
Restore this to the original logic to make it readable again
Regards
Mike
config_csdev_active = config_csdev_item; csdev->active_cscfg_ctxt = (void *)config_csdev_active; break;@@ -1097,7 +1116,11 @@ 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); @@ -1136,8 +1159,10 @@ 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}
-
Mike Leach