CVE-2015-8950 in Linux
Summary
by MITRE
arch/arm64/mm/dma-mapping.c in the Linux kernel before 4.0.3, as used in the ION subsystem in Android and other products, does not initialize certain data structures, which allows local users to obtain sensitive information from kernel memory by triggering a dma_mmap call.
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Analysis
by VulDB Data Team • 09/22/2022
The vulnerability described in CVE-2015-8950 represents a critical information disclosure flaw within the Linux kernel's ARM64 architecture implementation, specifically affecting versions prior to 4.0.3. This issue resides in the dma-mapping.c file and particularly impacts the ION subsystem commonly found in Android-based devices and other embedded systems. The vulnerability stems from improper initialization of data structures within the kernel's memory management subsystem, creating a pathway for local attackers to extract sensitive information from kernel memory spaces.
The technical nature of this vulnerability involves the failure to properly initialize certain kernel data structures during DMA (Direct Memory Access) mapping operations. When a dma_mmap call is triggered, the uninitialized memory regions contain residual data from previous operations, potentially exposing kernel stack contents, heap data, or other sensitive information that should not be accessible to user-space processes. This uninitialized data exposure occurs because the kernel does not properly zero out or initialize memory regions before they are made available for DMA operations, creating a classic information disclosure vector that aligns with CWE-1288, which specifically addresses uninitialized memory access patterns.
The operational impact of this vulnerability is significant for systems utilizing ARM64 architectures with affected kernel versions, particularly mobile devices and embedded systems running Android or similar operating systems. Local attackers who can execute code on the target system can exploit this vulnerability to gain access to kernel memory contents, potentially extracting cryptographic keys, session tokens, passwords, or other sensitive data that resides in memory. This type of information disclosure can lead to privilege escalation attacks where the extracted kernel memory contents might reveal security-relevant information that could be leveraged to further compromise the system. The vulnerability directly maps to attack techniques outlined in the ATT&CK framework under T1003 (OS Credential Dumping) and T1082 (System Information Discovery) where adversaries seek to extract sensitive information from system memory.
The exploitation of this vulnerability requires local access to the target system since it involves kernel-level memory operations that are not directly accessible from external network connections. However, the implications are severe because once an attacker achieves local execution, they can potentially access kernel memory regions that contain sensitive data from other processes or kernel subsystems. The vulnerability affects the ION subsystem which is commonly used for memory management in Android systems, making it particularly relevant for mobile device security and embedded system security. This type of memory disclosure vulnerability can have cascading effects on system security, as the extracted kernel memory information might contain information that could be used to bypass security controls or understand system internals for more sophisticated attacks.
Mitigation strategies for this vulnerability involve updating the Linux kernel to version 4.0.3 or later where the uninitialized data structure initialization has been corrected. System administrators should also implement proper kernel hardening measures including enabling kernel memory protection features such as stack canaries and kernel address space layout randomization. Additionally, monitoring for unusual DMA mapping operations and memory access patterns can help detect potential exploitation attempts. The fix implemented in the kernel version 4.0.3 specifically addresses the uninitialized memory issue by ensuring proper initialization of the affected data structures before they are used in DMA operations, thereby preventing the information disclosure that occurred in earlier versions. Organizations should prioritize patching this vulnerability as part of their regular security maintenance procedures, particularly those operating embedded systems or mobile devices that may be running vulnerable kernel versions.