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

Summary

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.

Timeline

1. Aug 22, 2024, 3:31 AM UTCCVE published
2. Sep 10, 2024, 3:32 PM UTCCISA SSVC assessment

   Exploitation: none · Automatable: no · Technical impact: partial

3. May 11, 2026, 6:49 PM UTCRecord last updated

Affected versions

• Linux Linux

  Version range not reported

• Linux Linux

  2.6.16

References 8