While loading firmware blobs parallely in different threads, it is possible
to free sysfs node of glue_dirs in device_del() from a thread while another
thread is trying to add subdir from device_add() in glue_dirs sysfs node.
CPU1 CPU2
fw_load_sysfs_fallback()
device_add()
get_device_parent()
class_dir_create_and_add()
kobject_add_internal()
create_dir() // glue_dir
fw_load_sysfs_fallback()
device_add()
get_device_parent()
kobject_get() //glue_dir
device_del()
cleanup_glue_dir()
kobject_del()
kobject_add()
kobject_add_internal()
create_dir() // in glue_dir
kernfs_create_dir_ns()
sysfs_remove_dir() //glue_dir->sd=NULL
sysfs_put() // free glue_dir->sd
kernfs_new_node()
kernfs_get(glue_dir)
Fix this race by making sure that kernfs_node for glue_dir is released only
when refcount for glue_dir kobj is 1.
Signed-off-by: Prateek Sood <[email protected]>
---
drivers/base/core.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/drivers/base/core.c b/drivers/base/core.c
index 4aeaa0c..3955d07 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -1820,12 +1820,15 @@ static inline struct kobject *get_glue_dir(struct
device *dev)
*/
static void cleanup_glue_dir(struct device *dev, struct kobject *glue_dir)
{
+ unsigned int refcount;
+
/* see if we live in a "glue" directory */
if (!live_in_glue_dir(glue_dir, dev))
return;
mutex_lock(&gdp_mutex);
- if (!kobject_has_children(glue_dir))
+ refcount = kref_read(&glue_dir->kref);
+ if (!kobject_has_children(glue_dir) && !--refcount)
kobject_del(glue_dir);
kobject_put(glue_dir);
mutex_unlock(&gdp_mutex);
--
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is a member of Code Aurora Forum, a Linux Foundation Collaborative Project.
