CVE-2016-10723 in Linux
Summary
by MITRE
** DISPUTED ** An issue was discovered in the Linux kernel through 4.17.2. Since the page allocator does not yield CPU resources to the owner of the oom_lock mutex, a local unprivileged user can trivially lock up the system forever by wasting CPU resources from the page allocator (e.g., via concurrent page fault events) when the global OOM killer is invoked. NOTE: the software maintainer has not accepted certain proposed patches, in part because of a viewpoint that "the underlying problem is non-trivial to handle."
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Analysis
by VulDB Data Team • 08/06/2024
The vulnerability described in CVE-2016-10723 represents a critical design flaw in the Linux kernel's memory management subsystem that can lead to complete system lockup under specific conditions. This issue exists within the page allocator mechanism and specifically targets the handling of the oom_lock mutex during out-of-memory scenarios. The problem manifests when the kernel's global OOM killer is invoked, creating a scenario where CPU resources become permanently unavailable to the system.
The technical root cause lies in the page allocator's failure to properly yield CPU resources back to the owner of the oom_lock mutex during critical memory allocation operations. When concurrent page fault events occur and the global OOM killer is triggered, an unprivileged local user can exploit this weakness by consuming excessive CPU resources from the page allocator. This creates a deadlock condition where the system becomes permanently unresponsive as it cannot release the necessary resources to continue normal operations. The vulnerability is classified as a local privilege escalation issue that requires no special privileges but can result in complete system compromise.
This flaw directly relates to CWE-667, which addresses improper locking mechanisms, and demonstrates how inadequate resource management can lead to system-wide failures. The operational impact is severe as it allows any local user to potentially cause a denial of service condition that affects the entire system. The vulnerability exploits the kernel's inability to properly handle resource contention during memory pressure scenarios, particularly when the OOM killer is activated as a last resort mechanism for memory management.
The attack vector is straightforward and can be executed by a local unprivileged user who simply needs to trigger concurrent page fault events while the system is under memory pressure. This creates a scenario where the page allocator becomes starved of CPU resources, preventing the system from properly handling the OOM killer's operations. The system lockup occurs because the mutex holder cannot release the lock due to the CPU resource exhaustion, creating a permanent deadlock condition. This vulnerability underscores the importance of proper resource management and mutex handling in kernel space operations, particularly during critical system failure scenarios.
Mitigation strategies should focus on implementing proper CPU yield mechanisms during page allocation operations and ensuring that the OOM killer can function without being blocked by resource contention issues. The kernel maintainers have expressed concerns about the complexity of addressing this fundamental problem, as it requires significant changes to core memory management algorithms. Organizations should monitor for kernel updates that address this specific issue and consider implementing additional system monitoring to detect potential resource contention scenarios that could lead to similar lockup conditions. The vulnerability highlights the need for comprehensive testing of memory management subsystems under stress conditions and proper handling of edge cases in resource allocation algorithms.