CVE-2024-26977 in Linux
Summary
by MITRE • 05/01/2024
In the Linux kernel, the following vulnerability has been resolved:
pci_iounmap(): Fix MMIO mapping leak
The #ifdef ARCH_HAS_GENERIC_IOPORT_MAP accidentally also guards iounmap(), which means MMIO mappings are leaked.
Move the guard so we call iounmap() for MMIO mappings.
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Analysis
by VulDB Data Team • 02/06/2026
The vulnerability CVE-2024-26977 addresses a critical memory management issue within the Linux kernel's PCI subsystem that results in memory mapping leaks during device I/O operations. This flaw specifically impacts how the kernel handles memory-mapped I/O (MMIO) mappings for PCI devices, creating a persistent resource leak that can degrade system performance and potentially lead to system instability over time. The issue manifests in the pci_iounmap() function where improper conditional compilation guards prevent correct cleanup of MMIO mappings, causing memory resources to remain allocated even after device drivers have completed their operations.
The technical root cause stems from an incorrect implementation of the ARCH_HAS_GENERIC_IOPORT_MAP compile-time conditional directive that inadvertently controls the execution path for the iounmap() function. This conditional logic was originally intended to provide generic I/O port mapping capabilities but was mistakenly applied to the MMIO unmapping process, creating a scenario where MMIO mappings are not properly released back to the system. The flaw exists in the kernel's device driver framework where the mapping and unmapping functions are not correctly synchronized, leading to resource accumulation that can eventually exhaust available memory resources. This type of memory leak represents a classic case of improper resource management that violates fundamental system reliability principles.
The operational impact of this vulnerability extends beyond simple memory consumption issues as it can cause progressive system degradation, particularly in environments with high PCI device activity or long-running systems. When MMIO mappings accumulate without proper cleanup, the system's virtual memory management becomes strained, potentially leading to allocation failures, reduced system responsiveness, and in severe cases, system crashes or hangs. The vulnerability affects any system running a Linux kernel version containing the flawed code, with the risk being proportional to the number of PCI devices and the frequency of device driver operations. This issue particularly impacts server environments, virtualization platforms, and embedded systems where PCI devices are heavily utilized and system stability is paramount.
Mitigation strategies for CVE-2024-26977 involve applying the official kernel patch that corrects the conditional compilation logic by moving the ARCH_HAS_GENERIC_IOPORT_MAP guard to the appropriate location where iounmap() is called for MMIO mappings. System administrators should prioritize updating their kernel versions to include this fix, particularly in production environments where PCI device utilization is high. The patch implementation aligns with industry best practices for memory management and resource cleanup as outlined in the Common Weakness Enumeration framework under CWE-404, which addresses improper resource cleanup. Additionally, organizations should implement monitoring solutions to detect memory usage patterns that may indicate resource leaks, and consider implementing regular system maintenance routines that include kernel updates and memory diagnostics to prevent escalation of this vulnerability into more serious system stability issues.