In the Linux kernel, the following vulnerability has been resolved:
btrfs: fix double free in create_space_info_sub_group() error path
When kobject_init_and_add() fails, the call chain is:
create_space_info_sub_group() -> btrfs_sysfs_add_space_info_type() -> kobject_init_and_add() -> failure -> kobject_put(&sub_group->kobj) -> space_info_release() -> kfree(sub_group)
Then control returns to create_space_info_sub_group(), where:
btrfs_sysfs_add_space_info_type() returns error -> kfree(sub_group)
Thus, sub_group is freed twice.
Keep parent->sub_group[index] = NULL for the failure path, but after btrfs_sysfs_add_space_info_type() has called kobject_put(), let the kobject release callback handle the cleanup.