CVE-2017-6001 in Linux
Summary
by MITRE
Race condition in kernel/events/core.c in the Linux kernel before 4.9.7 allows local users to gain privileges via a crafted application that makes concurrent perf_event_open system calls for moving a software group into a hardware context. NOTE: this vulnerability exists because of an incomplete fix for CVE-2016-6786.
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Analysis
by VulDB Data Team • 02/19/2017
The vulnerability described in CVE-2017-6001 represents a critical race condition within the Linux kernel's performance monitoring subsystem, specifically in the kernel/events/core.c file. This flaw affects Linux kernel versions prior to 4.9.7 and enables local privilege escalation through a sophisticated attack vector involving concurrent perf_event_open system calls. The vulnerability stems from an incomplete remediation of CVE-2016-6786, creating a persistent security gap that adversaries can exploit to elevate their privileges from unprivileged user status to root access. The race condition occurs during the process of moving a software group into a hardware context, which is a fundamental operation within the kernel's performance monitoring framework.
The technical implementation of this vulnerability relies on the manipulation of concurrent system calls to exploit timing dependencies in the kernel's event handling logic. When a crafted application makes multiple perf_event_open system calls simultaneously, it can trigger a race condition that leads to improper synchronization between different kernel threads managing performance events. This race condition manifests when the kernel attempts to transition a software performance monitoring group into a hardware context, creating opportunities for memory corruption or improper privilege handling. The flaw operates at the kernel level where the security boundaries are not properly enforced during concurrent access to shared kernel resources, allowing an attacker to manipulate the kernel's internal state through carefully timed system calls.
The operational impact of CVE-2017-6001 is severe as it provides local attackers with a direct path to privilege escalation without requiring any network access or external attack vectors. Once exploited, this vulnerability allows an attacker to gain root privileges on the affected system, potentially leading to complete system compromise. The attack requires only local execution capabilities and can be performed by any user with the ability to run applications on the target system. This makes it particularly dangerous in multi-user environments where attackers might already have limited access to execute code. The vulnerability's exploitation is relatively straightforward once the attacker understands the timing requirements and system call patterns needed to trigger the race condition, making it a preferred target for privilege escalation attacks in various security contexts.
Mitigation strategies for CVE-2017-6001 focus primarily on upgrading to kernel versions 4.9.7 or later where the vulnerability has been properly addressed. System administrators should prioritize kernel updates across all affected systems, particularly those running older kernel versions that may be exposed to this vulnerability. Additional protective measures include implementing strict process monitoring to detect unusual patterns of perf_event_open system calls and applying kernel security modules that can help detect and prevent exploitation attempts. The fix for this vulnerability aligns with common security practices for race condition mitigation, including proper locking mechanisms and atomic operations to ensure thread safety during concurrent access to shared kernel resources. Organizations should also consider implementing kernel hardening techniques and monitoring solutions that can help detect potential exploitation attempts. This vulnerability demonstrates the importance of thorough vulnerability analysis and proper testing of security patches, as the incomplete fix for CVE-2016-6786 created the conditions for CVE-2017-6001 to persist. The attack pattern for this vulnerability falls under the ATT&CK technique of privilege escalation through kernel exploits, specifically targeting the kernel's performance monitoring subsystem as a vector for unauthorized access. From a CWE perspective, this vulnerability maps to CWE-362, which describes race conditions in kernel-level operations, highlighting the critical nature of proper synchronization mechanisms in operating system components.