arm64/mpam: remove kernfs_get() calls() and add kernfs_put() calls to prevent refcount leak

hulk inclusion
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I61CPK


CVE: NA

--------------------------------

Refer to the two commits:

  commit fd8d9db3 ("x86/resctrl: Remove superfluous kernfs_get() calls
  to prevent refcount leak")

  commit 75899924 ("x86/resctrl: Add necessary kernfs_put() calls to
  prevent refcount leak")

there are some places where a kernfs_node reference is obtained
without a corresponding release. The excessive amount of reference
count on kernfs nodes will never be dropped to 0 and the kernfs nodes
will never be freed in the call paths of rmdir and umount.
It leads to reference count leak and kernfs_node_cache memory leak.

For example, reference count leak is observed in these two cases:

  (1) mount -t resctrl none /sys/fs/resctrl
      mkdir /sys/fs/resctrl/c1
      mkdir /sys/fs/resctrl/c1/mon_groups/m1
      umount /sys/fs/resctrl

  (2) mkdir /sys/fs/resctrl/c1
      mkdir /sys/fs/resctrl/c1/mon_groups/m1
      rmdir /sys/fs/resctrl/c1

Superfluous kernfs_get() calls are removed from two areas:

  (1) In call paths of mount and mkdir, when kernfs nodes for "info",
  "mon_groups" and "mon_data" directories and sub-directories are
  created, the reference count of newly created kernfs node is set to 1.
  But after kernfs_create_dir() returns, superfluous kernfs_get() are
  called to take an additional reference.

  (2) kernfs_get() calls in rmdir call paths.

Necessary kernfs_put() calls are added by following changes:

  (1) Introduce rdtgroup removal helper rdtgroup_remove() to wrap up
  kernfs_put() and kfree().

  (2) Call rdtgroup_remove() in rdtgroup removal path where the rdtgroup
  structure is about to be freed by kfree().

  (3) Call rdtgroup_remove() or kernfs_put() as appropriate in the error
  exit paths of mkdir where an extra reference is taken by kernfs_get().

Signed-off-by: Wang ShaoBo <bobo.shaobowang@huawei.com>
Signed-off-by: Jialin Zhang <zhangjialin11@huawei.com>
Reviewed-by: Xie XiuQi <xiexiuqi@huawei.com>
Reviewed-by: Xie XiuQi <xiexiuqi@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>