CVE-2021-47147 in Linux
Summary
by MITRE • 03/25/2024
In the Linux kernel, the following vulnerability has been resolved:
ptp: ocp: Fix a resource leak in an error handling path
If an error occurs after a successful 'pci_ioremap_bar()' call, it must be undone by a corresponding 'pci_iounmap()' call, as already done in the remove function.
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Analysis
by VulDB Data Team • 09/16/2025
The vulnerability identified as CVE-2021-47147 represents a resource leak in the Linux kernel's Precision Time Protocol (PTP) implementation specifically within the Open Compute Project (OCP) driver. This issue manifests in the error handling path of the PTP subsystem where proper resource cleanup mechanisms are not consistently applied. The flaw occurs when the kernel attempts to map PCI memory regions for hardware communication but encounters an error subsequent to a successful pci_ioremap_bar() operation. The root cause lies in the asymmetric handling of resource management between normal execution paths and error conditions, creating a scenario where mapped memory regions remain allocated even when the driver fails to initialize properly.
The technical implementation of this vulnerability involves the PTP subsystem's interaction with PCI hardware through the OCP driver framework. When the driver attempts to establish communication with PTP hardware devices, it performs a pci_ioremap_bar() call to map the device's memory-mapped I/O regions into the kernel's virtual address space. However, if an error condition occurs during subsequent initialization steps, the corresponding cleanup function pci_iounmap() is not invoked to release the previously mapped resources. This resource leak directly violates fundamental kernel memory management principles and creates a persistent allocation that consumes system resources without proper deallocation. The vulnerability is categorized under CWE-404, which specifically addresses improper resource release or unbalanced resource management, making it a classic example of resource management failure in kernel space.
The operational impact of CVE-2021-47147 extends beyond simple memory consumption to potentially compromise system stability and availability. While individual resource leaks may appear minor, in kernel contexts where such operations can occur repeatedly during device initialization, the cumulative effect leads to progressive memory exhaustion. This condition can manifest as system performance degradation, increased memory pressure, and in severe cases, system instability or crashes. The vulnerability particularly affects systems running Linux kernels with PTP support and OCP hardware configurations, making it relevant to data center environments, network infrastructure, and industrial control systems that rely on precise timing protocols. The issue demonstrates how seemingly small inconsistencies in error handling can create significant operational risks in kernel-level code, as highlighted by ATT&CK technique T1547.001 which addresses kernel modules and drivers as entry points for system compromise.
Mitigation strategies for this vulnerability require careful attention to proper resource management practices within kernel drivers. System administrators should prioritize updating to kernel versions that contain the patched implementation, which ensures that all error paths properly invoke pci_iounmap() following successful pci_ioremap_bar() calls. The fix implements consistent resource management by ensuring that any memory mapping operations performed during driver initialization are properly cleaned up regardless of whether the initialization succeeds or fails. Additionally, comprehensive testing of driver initialization sequences and error handling paths should be conducted to prevent similar resource management issues. Organizations should also implement monitoring for memory usage patterns that might indicate resource exhaustion symptoms, particularly in systems with high PTP activity. The vulnerability underscores the importance of following established kernel development practices and conducting thorough testing of error conditions to prevent resource leaks that could compromise system integrity and availability.