CVE-2022-48699 in Linux
Summary
by MITRE • 05/03/2024
In the Linux kernel, the following vulnerability has been resolved:
sched/debug: fix dentry leak in update_sched_domain_debugfs
Kuyo reports that the pattern of using debugfs_remove(debugfs_lookup()) leaks a dentry and with a hotplug stress test, the machine eventually runs out of memory.
Fix this up by using the newly created debugfs_lookup_and_remove() call instead which properly handles the dentry reference counting logic.
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Analysis
by VulDB Data Team • 09/29/2025
The vulnerability identified as CVE-2022-48699 represents a critical memory management flaw within the Linux kernel's scheduling subsystem, specifically affecting the debugfs interface used for scheduler domain debugging. This issue manifests as a dentry leak that occurs during the execution of the update_sched_domain_debugfs function, which is part of the kernel's scheduler debugging infrastructure. The vulnerability was discovered through extensive stress testing involving hotplug operations, where the cumulative effect of improper reference counting led to systematic memory exhaustion across the system.
The technical root cause stems from improper handling of debugfs dentry references within the scheduler domain debugging interface. When debugfs_remove() is called with the result of debugfs_lookup(), the function fails to properly decrement the reference count of the dentry structure, leading to a memory leak that accumulates over time. This flaw directly violates proper resource management principles and represents a classic case of improper reference counting that can be categorized under CWE-404, which addresses improper resource management. The vulnerability specifically impacts the kernel's ability to properly clean up debugging interface resources, causing a gradual degradation of system memory availability.
The operational impact of this vulnerability extends beyond simple memory consumption, as it can lead to complete system instability and potential denial of service conditions. During hotplug stress testing scenarios, the memory leak compounds rapidly, eventually exhausting available memory resources and forcing the system to either crash or become unresponsive. This type of vulnerability aligns with ATT&CK technique T1499.001, which covers resource exhaustion attacks, and specifically targets the system's memory management capabilities. The vulnerability affects systems running Linux kernel versions that include the affected scheduler debugging code, particularly those utilizing hotplug functionality or extensive debugging operations.
The fix implemented for CVE-2022-48699 addresses the root cause by replacing the problematic debugfs_remove(debugfs_lookup()) pattern with the newly introduced debugfs_lookup_and_remove() function. This replacement properly handles the dentry reference counting logic by ensuring that when a dentry is looked up and subsequently removed, the reference count is appropriately managed and decremented. This solution directly addresses the improper resource management issue and aligns with best practices for kernel development. The fix demonstrates proper adherence to kernel memory management protocols and prevents the accumulation of unreferenced dentry structures that would otherwise persist in memory indefinitely. The mitigation approach follows established kernel development patterns for handling debugfs interfaces and ensures that all debugging resources are properly cleaned up when no longer needed, thereby preventing the memory exhaustion scenario that could lead to system instability and denial of service conditions.