CVE-2016-5728 in Linux
Summary
by MITRE
Race condition in the vop_ioctl function in drivers/misc/mic/vop/vop_vringh.c in the MIC VOP driver in the Linux kernel before 4.6.1 allows local users to obtain sensitive information from kernel memory or cause a denial of service (memory corruption and system crash) by changing a certain header, aka a "double fetch" vulnerability.
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Analysis
by VulDB Data Team • 02/17/2019
The CVE-2016-5728 vulnerability represents a critical race condition flaw within the MIC VOP driver component of the Linux kernel, specifically affecting versions prior to 4.6.1. This vulnerability resides in the vop_ioctl function located in drivers/misc/mic/vop/vop_vringh.c, where a double fetch condition occurs during header processing operations. The flaw enables local attackers to manipulate kernel memory through carefully crafted ioctl calls that modify specific header structures, creating a window where the same memory location can be accessed twice with potentially different values during concurrent operations. The vulnerability stems from inadequate synchronization mechanisms that fail to prevent simultaneous access to shared kernel data structures during ioctl processing. This type of race condition falls under CWE-362, which specifically addresses concurrent execution using lock or lock-free synchronization mechanisms, and more broadly aligns with CWE-367, which covers the use of a broken or weak cryptographic algorithm.
The operational impact of this vulnerability extends beyond simple information disclosure to encompass potential system instability and complete system crashes. Local users can exploit this condition to either extract sensitive kernel memory contents through information leakage or to trigger memory corruption that results in system crashes and denial of service conditions. The double fetch nature of the vulnerability means that an attacker can manipulate the header data between the first and second memory fetch operations, potentially causing the kernel to process corrupted or unexpected values. This creates a scenario where the attacker can influence the execution flow of the kernel code, leading to unpredictable behavior including privilege escalation possibilities. The vulnerability is particularly concerning because it operates at the kernel level, where successful exploitation can result in complete system compromise, making it a prime target for advanced persistent threat actors seeking to establish persistent access to affected systems.
From an attack perspective, this vulnerability follows patterns consistent with the ATT&CK framework's privilege escalation techniques, specifically targeting kernel-level weaknesses to gain elevated system privileges. The exploitation requires local access to the system but does not require special privileges beyond basic user access, making it particularly dangerous in multi-user environments where attackers can leverage this flaw to escalate their privileges. The vulnerability demonstrates poor defensive programming practices where proper locking mechanisms and memory access validation were not implemented to prevent concurrent access to critical kernel data structures. Mitigation strategies should focus on implementing proper synchronization primitives such as mutex locks or spinlocks to prevent the race condition, along with comprehensive input validation and header structure verification. System administrators should prioritize applying kernel updates to version 4.6.1 or later where this vulnerability has been addressed through proper locking mechanisms and race condition prevention measures. The fix typically involves adding appropriate synchronization code to ensure that header data cannot be modified between the first and second fetch operations, thereby preventing the double fetch scenario that enables the exploit. Organizations should also consider implementing kernel hardening measures such as stack canaries, kernel address space layout randomization, and other security controls that make exploitation more difficult even if such vulnerabilities are present in other components of the system.