In the Linux kernel, the following vulnerability has been resolved:

configfs: fix a race in configfs_{,un}register_subsystem()

When configfs_register_subsystem() or configfs_unregister_subsystem()
is executing link_group() or unlink_group(),
it is possible that two processes add or delete list concurrently.
Some unfortunate interleavings of them can cause kernel panic.

One of cases is:
A --> B --> C --> D
A <-- B <-- C <-- D

     delete list_head *B        |      delete list_head *C
--------------------------------|-----------------------------------
configfs_unregister_subsystem   |   configfs_unregister_subsystem
  unlink_group                  |     unlink_group
    unlink_obj                  |       unlink_obj
      list_del_init             |         list_del_init
        __list_del_entry        |           __list_del_entry
          __list_del            |             __list_del
            // next == C        |
            next->prev = prev   |
                                |               next->prev = prev
            prev->next = next   |
                                |                 // prev == B
                                |                 prev->next = next

Fix this by adding mutex when calling link_group() or unlink_group(),
but parent configfs_subsystem is NULL when config_item is root.
So I create a mutex configfs_subsystem_mutex.

kernel.org https://git.kernel.org/stable/c/3aadfd46858b1f64d4d6a0654b863e21aabff975 [No types assigned]

kernel.org https://git.kernel.org/stable/c/40805099af11f68c5ca7dbcfacf455da8f99f622 [No types assigned]

kernel.org https://git.kernel.org/stable/c/84ec758fb2daa236026506868c8796b0500c047d [No types assigned]

kernel.org https://git.kernel.org/stable/c/a37024f7757c25550accdebf49e497ad6ae239fe [No types assigned]

kernel.org https://git.kernel.org/stable/c/a7ab53d3c27dfe83bb594456b9f38a37796ec39b [No types assigned]

kernel.org https://git.kernel.org/stable/c/b7e2b91fcb5c78c414e33dc8d50642e307ca0c5a [No types assigned]

kernel.org https://git.kernel.org/stable/c/d1654de19d42f513b6cfe955cc77e7f427e05a77 [No types assigned]

kernel.org https://git.kernel.org/stable/c/e7a66dd2687758718eddd79b542a95cf3aa488cc [No types assigned]