[PATCH 2/6] nilfs2: fix NULL pointer in nilfs_##name##_attr_release

[Ryusuke Konishi]

From: Nanyong Sun <sunnanyong@xxxxxxxxxx>

In nilfs_##name##_attr_release, kobj->parent should not be
referenced because it is a NULL pointer. The release() method of
kobject is always called in kobject_put(kobj), in the implementation
of kobject_put(), the kobj->parent will be assigned as NULL before
call the release() method. So just use kobj to get the subgroups,
which is more efficient and can fix a NULL pointer reference problem.

Link: https://lkml.kernel.org/r/20210629022556.3985106-3-sunnanyong@xxxxxxxxxx
Signed-off-by: Nanyong Sun <sunnanyong@xxxxxxxxxx>
Signed-off-by: Ryusuke Konishi <konishi.ryusuke@xxxxxxxxx>
---
 fs/nilfs2/sysfs.c | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/fs/nilfs2/sysfs.c b/fs/nilfs2/sysfs.c
index b6a48492fed2..43f660beb9b4 100644
--- a/fs/nilfs2/sysfs.c
+++ b/fs/nilfs2/sysfs.c
@@ -64,11 +64,9 @@
 #define NILFS_DEV_INT_GROUP_TYPE(name, parent_name) \
 static void nilfs_##name##_attr_release(struct kobject *kobj) \
 { \
-	struct nilfs_sysfs_##parent_name##_subgroups *subgroups; \
-	struct the_nilfs *nilfs = container_of(kobj->parent, \
-						struct the_nilfs, \
-						ns_##parent_name##_kobj); \
-	subgroups = nilfs->ns_##parent_name##_subgroups; \
+	struct nilfs_sysfs_##parent_name##_subgroups *subgroups = container_of(kobj, \
+						struct nilfs_sysfs_##parent_name##_subgroups, \
+						sg_##name##_kobj); \
 	complete(&subgroups->sg_##name##_kobj_unregister); \
 } \
 static struct kobj_type nilfs_##name##_ktype = { \
-- 
1.8.3.1