CVE-2022-48931 in Linux
Summary
by MITRE • 08/22/2024
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.
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Analysis
by VulDB Data Team • 06/19/2025
The vulnerability described in CVE-2022-48931 resides within the Linux kernel's configfs implementation, specifically affecting the synchronization mechanisms during subsystem registration and unregistration operations. This flaw manifests as a race condition that can lead to kernel panic conditions when multiple processes attempt concurrent modifications to the same list structures. The issue impacts the configfs subsystem which provides a filesystem interface for configuring kernel objects, making it a critical component for system administration and device management operations. The vulnerability directly relates to CWE-362, which identifies race conditions in concurrent programming environments where multiple threads or processes access shared resources without proper synchronization.
The technical flaw occurs during the execution of configfs_register_subsystem() and configfs_unregister_subsystem() functions when they invoke link_group() or unlink_group() operations. These functions manipulate linked list structures containing configfs objects, and the lack of proper synchronization between concurrent processes creates scenarios where list integrity can be compromised. The race condition specifically emerges when one process attempts to delete a list entry while another process simultaneously modifies the same list structure, leading to memory corruption and potential system crashes. The problematic interleaving pattern shows how concurrent execution paths can result in dangling pointers and corrupted list links, where the next and prev pointers of list elements become inconsistent with the actual list structure. This represents a classic example of a data race condition that violates the fundamental principles of concurrent programming and system stability.
The operational impact of this vulnerability extends beyond simple system instability to potentially compromise entire system operations, especially in environments where configfs is actively used for device configuration and kernel object management. Attackers could exploit this race condition to cause denial of service conditions through kernel panics, effectively rendering systems unresponsive and requiring manual intervention for recovery. The vulnerability affects systems running Linux kernels that implement the configfs subsystem, particularly those managing device drivers, network configurations, or other kernel objects through this interface. The consequences include potential data loss, system downtime, and the possibility of exploitation for privilege escalation attacks, making this a significant security concern for enterprise and embedded systems that rely on kernel-level configuration mechanisms.
Mitigation strategies for CVE-2022-48931 involve implementing proper synchronization mechanisms around the affected list operations. The fix employs a dedicated mutex named configfs_subsystem_mutex to protect the critical sections during link_group() and unlink_group() operations, preventing concurrent access to shared list structures. This approach aligns with ATT&CK technique T1068 which involves privilege escalation through kernel-level vulnerabilities, and addresses the root cause by ensuring atomicity of list manipulation operations. Organizations should ensure their Linux systems are updated with patches that implement this mutex-based synchronization, particularly in environments where configfs is actively utilized. The mitigation also requires careful consideration of performance implications, as the added synchronization may introduce slight overhead to subsystem registration and unregistration operations, though this is deemed acceptable given the security benefits and the low probability of the race condition occurring in normal system operation.