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Message-Id: <20250514161951.3427590-4-yeoreum.yun@arm.com>
Date: Wed, 14 May 2025 17:19:51 +0100
From: Yeoreum Yun <yeoreum.yun@....com>
To: suzuki.poulose@....com,
mike.leach@...aro.org,
james.clark@...aro.org,
alexander.shishkin@...ux.intel.com,
leo.yan@....com
Cc: coresight@...ts.linaro.org,
linux-arm-kernel@...ts.infradead.org,
linux-kernel@...r.kernel.org,
Yeoreum Yun <yeoreum.yun@....com>
Subject: [PATCH v6 3/3] 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: f8cce2ff3c04 ("coresight: syscfg: Add API to activate and enable configurations")
Signed-off-by: Yeoreum Yun <yeoreum.yun@....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}
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