CVE-2015-8944 in Android
Summary
by MITRE
The ioresources_init function in kernel/resource.c in the Linux kernel through 4.7, as used in Android before 2016-08-05 on Nexus 6 and 7 (2013) devices, uses weak permissions for /proc/iomem, which allows local users to obtain sensitive information by reading this file, aka Android internal bug 28814213 and Qualcomm internal bug CR786116. NOTE: the permissions may be intentional in most non-Android contexts.
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Analysis
by VulDB Data Team • 09/12/2022
The vulnerability identified as CVE-2015-8944 represents a significant information disclosure issue within the Linux kernel's resource management subsystem. This flaw specifically affects the ioresources_init function located in kernel/resource.c, which is responsible for initializing the kernel's resource management structures. The vulnerability manifests in Linux kernel versions through 4.7 and was particularly prevalent in Android implementations prior to the 2016-08-05 security patch release for Nexus 6 and Nexus 7 (2013) devices. The core issue lies in the improper permission settings applied to the /proc/iomem virtual file system entry, which exposes critical hardware resource information to unauthorized local users.
The technical exploitation of this vulnerability stems from the weak permissions assigned to the /proc/iomem file, which typically should be restricted to prevent unauthorized access to kernel memory mappings and hardware resource allocations. Under normal circumstances, this file should only be accessible to privileged processes or root users, but the flawed implementation allowed any local user to read its contents. This exposure enables attackers to obtain detailed information about memory regions, I/O port mappings, and other sensitive kernel resource allocations that could reveal system architecture details and potentially aid in further exploitation attempts. The vulnerability aligns with CWE-200, which specifically addresses "Information Exposure Through Output Redirection," and demonstrates how improper access control can lead to information disclosure.
The operational impact of CVE-2015-8944 extends beyond simple information gathering, as the leaked information can serve as a foundation for more sophisticated attacks. Local users who can read /proc/iomem gain visibility into the kernel's memory layout, which can be instrumental in bypassing security mechanisms such as address space layout randomization and kernel address leaks. Attackers can leverage this information to perform kernel exploitation techniques, including kernel pointer dereferencing and memory corruption attacks that rely on knowing the actual addresses of kernel structures and functions. This vulnerability particularly affects mobile device security, where the Android implementation's kernel is used in widely deployed consumer devices, making the impact more severe given the large user base. The issue was referenced in Android internal bug 28814213 and Qualcomm internal bug CR786116, highlighting the severity and widespread nature of the problem across different device manufacturers.
The mitigation strategy for CVE-2015-8944 involves implementing proper permission controls on the /proc/iomem file and ensuring that kernel resource management functions properly enforce access restrictions. System administrators should apply the relevant security patches released by the Linux kernel community and Android security teams, particularly those addressing the specific kernel versions mentioned in the vulnerability description. The fix typically involves modifying the ioresources_init function to properly set permissions on the /proc/iomem file, ensuring that only appropriately privileged processes can access the sensitive resource information. Organizations should also consider implementing additional monitoring and logging for access attempts to sensitive kernel virtual files, as this can help detect potential exploitation attempts. The vulnerability demonstrates the importance of proper privilege separation in kernel space and aligns with ATT&CK technique T1068, which covers "Exploitation for Privilege Escalation," as attackers can use information disclosure to gain insights necessary for privilege escalation attacks. Furthermore, this vulnerability illustrates the broader category of privilege escalation through information disclosure, which is categorized under ATT&CK technique T1082, "System Information Discovery," where adversaries gather information about the system to plan further attacks. The fix for this vulnerability also reinforces the principle of least privilege enforcement, which is fundamental to secure system design and aligns with security frameworks such as the NIST Cybersecurity Framework and ISO 27001 standards for information security management.