CVE-2022-48931configfs: fix a race in configfs_{,un}register_subsystem()

Official description

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.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/40805099af11f68c5ca7dbcfacf455da8f99f622
• https://git.kernel.org/stable/c/d1654de19d42f513b6cfe955cc77e7f427e05a77
• https://git.kernel.org/stable/c/a37024f7757c25550accdebf49e497ad6ae239fe
• https://git.kernel.org/stable/c/b7e2b91fcb5c78c414e33dc8d50642e307ca0c5a
• https://git.kernel.org/stable/c/a7ab53d3c27dfe83bb594456b9f38a37796ec39b
• https://git.kernel.org/stable/c/e7a66dd2687758718eddd79b542a95cf3aa488cc
• https://git.kernel.org/stable/c/3aadfd46858b1f64d4d6a0654b863e21aabff975
• https://git.kernel.org/stable/c/84ec758fb2daa236026506868c8796b0500c047d