CVE-2023-53402 in Linux
Summary
by MITRE • 09/18/2025
In the Linux kernel, the following vulnerability has been resolved:
kernel/printk/index.c: fix memory leak with using debugfs_lookup()
When calling debugfs_lookup() the result must have dput() called on it, otherwise the memory will leak over time. To make things simpler, just call debugfs_lookup_and_remove() instead which handles all of the logic at once.
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Analysis
by VulDB Data Team • 12/13/2025
The vulnerability identified as CVE-2023-53402 represents a memory leak issue within the Linux kernel's printk subsystem, specifically affecting the debugfs_lookup() function implementation in kernel/printk/index.c. This flaw demonstrates a classic resource management oversight that can lead to gradual system degradation and potential denial of service conditions. The vulnerability resides in the kernel's debugging filesystem interface where improper handling of debugfs directory entries results in unreleased memory allocations that accumulate over time. The issue directly impacts the kernel's ability to efficiently manage memory resources, particularly within the printk subsystem that handles kernel message output and debugging functionality.
The technical root cause of this vulnerability stems from improper reference counting management when working with debugfs directory entries. When debugfs_lookup() is invoked to locate a directory entry within the debug filesystem, the function returns a reference to the dentry structure that must be explicitly released using dput() to prevent memory leaks. This pattern follows standard Linux kernel conventions where all acquired references to filesystem objects must be properly released to maintain memory integrity. The flaw occurs when developers fail to call dput() on the returned dentry reference, causing the underlying memory structures to remain allocated indefinitely. This memory leak becomes particularly problematic in systems that frequently access debugfs interfaces or in long-running kernel processes that repeatedly call debugfs_lookup() without proper cleanup.
The operational impact of this memory leak vulnerability extends beyond simple resource consumption, potentially leading to system instability and performance degradation over extended periods of operation. As the leaked memory accumulates, it can contribute to memory pressure that affects other kernel subsystems and may eventually cause system slowdowns or even kernel crashes in severe cases. The vulnerability is particularly concerning in embedded systems or server environments where kernel processes run continuously and memory management is critical for maintaining system reliability. Systems utilizing extensive debugging capabilities or those with high-frequency printk operations are at greater risk of experiencing noticeable performance impacts due to the gradual accumulation of leaked memory. The vulnerability affects all Linux kernel versions that implement the problematic debugfs_lookup() usage pattern and could potentially be exploited to create persistent resource exhaustion conditions.
The resolution for this vulnerability involves implementing a more robust approach by replacing direct calls to debugfs_lookup() with debugfs_lookup_and_remove() which automatically handles the complete lifecycle management of the debugfs entry. This solution addresses the underlying issue by ensuring proper cleanup operations occur automatically without requiring developers to remember specific reference management patterns. The fix aligns with established kernel development practices that emphasize using higher-level functions that encapsulate proper resource management logic. This approach reduces the likelihood of similar memory leak vulnerabilities in the future by eliminating the need for manual dentry reference management. The solution also provides better integration with kernel memory management subsystems and follows the principle of least privilege by ensuring that all resources are properly accounted for and released. This remediation strategy demonstrates the importance of using well-tested kernel APIs that handle resource management internally rather than relying on manual reference counting that is prone to developer error. The fix essentially eliminates the attack surface for this particular class of memory leak vulnerability while maintaining the intended functionality of the debugfs interface.
This vulnerability maps to CWE-404, which describes improper resource management, and specifically relates to improper cleanup of kernel memory resources. From an ATT&CK perspective, this represents a resource exhaustion technique that could be leveraged by adversaries to degrade system performance or create denial of service conditions. The vulnerability demonstrates how seemingly minor resource management oversights in kernel code can have significant operational impacts, highlighting the critical importance of proper reference counting and memory management practices in kernel development. The fix implementation also reflects best practices for kernel security by using established kernel APIs that provide automatic resource cleanup mechanisms.