CVE-2017-7616 in Linux
Summary
by MITRE
Incorrect error handling in the set_mempolicy and mbind compat syscalls in mm/mempolicy.c in the Linux kernel through 4.10.9 allows local users to obtain sensitive information from uninitialized stack data by triggering failure of a certain bitmap operation.
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Analysis
by VulDB Data Team • 11/28/2022
The vulnerability identified as CVE-2017-7616 represents a critical information disclosure flaw within the Linux kernel's memory management subsystem. This issue resides in the mm/mempolicy.c file and affects kernel versions through 4.10.9, making it a widespread concern across numerous Linux distributions that rely on these kernel versions. The vulnerability specifically targets the set_mempolicy and mbind compat syscalls which are responsible for memory policy management in Linux systems. These syscalls handle memory allocation policies for processes and are essential components of the kernel's memory management framework that govern how memory is allocated and managed across different NUMA nodes.
The technical flaw manifests through improper error handling mechanisms within the bitmap operation processing within these syscalls. When certain bitmap operations fail during memory policy configuration, the kernel fails to properly initialize stack variables before returning sensitive information to user-space applications. This occurs because the error handling code path does not adequately clear or initialize memory locations that contain uninitialized stack data from previous operations. The vulnerability is particularly insidious because it allows local attackers who have access to the system to extract potentially sensitive information from kernel stack memory, which may include previously stored data from other processes, kernel memory structures, or even cryptographic keys that were temporarily held in memory.
The operational impact of this vulnerability extends beyond simple information disclosure, as it creates potential attack vectors for privilege escalation and data leakage attacks. Local users can exploit this flaw to gain access to uninitialized memory contents that may contain sensitive data from other processes or kernel operations, potentially exposing credentials, cryptographic keys, or other confidential information. The vulnerability is classified under CWE-248 as an "Uncaught Exception" and aligns with ATT&CK technique T1059.001 for executing malicious code through system calls. This flaw particularly affects systems where multiple processes are running with different memory policies, as the uninitialized stack data from one process may be accessible to another through this vulnerability.
Mitigation strategies for CVE-2017-7616 involve applying the official kernel patches released by the Linux kernel security team, which properly initialize stack variables before returning from error handling paths in the affected syscalls. System administrators should prioritize updating their kernel versions to 4.10.10 or later, where the vulnerability has been addressed through proper memory initialization in the error handling code paths. Additionally, monitoring systems should be implemented to detect unusual memory access patterns that might indicate exploitation attempts. Organizations should also consider implementing kernel lockdown mechanisms and restricting local user access where possible. The vulnerability demonstrates the critical importance of proper error handling in kernel code and highlights the potential consequences of uninitialized memory access patterns in system-level programming, particularly when dealing with memory management operations that are fundamental to system stability and security.