CVE-2016-7911 in Android
Summary
by MITRE • 01/25/2023
Race condition in the get_task_ioprio function in block/ioprio.c in the Linux kernel before 4.6.6 allows local users to gain privileges or cause a denial of service (use-after-free) via a crafted ioprio_get system call.
Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.
Analysis
by VulDB Data Team • 01/25/2023
The vulnerability identified as CVE-2016-7911 represents a critical race condition within the Linux kernel's block subsystem, specifically in the get_task_ioprio function located in block/ioprio.c. This flaw exists in kernel versions prior to 4.6.6 and exposes systems to potential privilege escalation or denial of service attacks through malicious manipulation of the ioprio_get system call. The race condition occurs during the handling of I/O priority operations for processes, creating a window where concurrent access to shared kernel data structures can result in inconsistent states. The vulnerability is classified under CWE-367, which specifically addresses Time-of-Check to Time-of-Use (TOCTOU) flaws, where the system state changes between the time a check is performed and when the action is executed. This particular race condition manifests as a use-after-free vulnerability, where memory that has been deallocated is still being accessed, potentially leading to arbitrary code execution or system instability.
The operational impact of this vulnerability extends across multiple attack vectors within the Linux kernel environment. Local attackers with minimal privileges can exploit this weakness to escalate their privileges to root level, effectively bypassing traditional security boundaries. The use-after-free condition can also be leveraged to cause system crashes or denial of service scenarios, making it particularly dangerous in production environments where system stability is paramount. The vulnerability's exploitation requires careful crafting of the ioprio_get system call parameters to trigger the race condition, typically involving concurrent threads or processes that manipulate I/O priority settings while the kernel processes these requests. This attack pattern aligns with ATT&CK technique T1068, which covers the exploitation of local privilege escalation vulnerabilities, and T1499, which addresses the exploitation of system resource abuse through denial of service mechanisms.
Mitigation strategies for CVE-2016-7911 primarily focus on kernel version updates and system hardening measures. Organizations must immediately apply the patched kernel version 4.6.6 or later, which incorporates proper synchronization mechanisms to prevent the race condition from occurring. The fix typically involves implementing appropriate locking mechanisms or atomic operations around the vulnerable code paths to ensure exclusive access to shared resources during I/O priority operations. Additionally, system administrators should consider implementing monitoring solutions to detect anomalous ioprio_get system call patterns that might indicate exploitation attempts. Security configurations can be enhanced by restricting access to I/O priority manipulation capabilities through capability-based access controls or by implementing mandatory access controls that limit which processes can modify I/O priorities. The vulnerability also underscores the importance of regular kernel security audits and the application of security patches in maintaining system integrity, as this race condition represents a fundamental flaw in kernel thread synchronization that could potentially be exploited in other similar contexts.