CVE-2016-9084 in Linux
Summary
by MITRE
drivers/vfio/pci/vfio_pci_intrs.c in the Linux kernel through 4.8.11 misuses the kzalloc function, which allows local users to cause a denial of service (integer overflow) or have unspecified other impact by leveraging access to a vfio PCI device file.
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Analysis
by VulDB Data Team • 10/04/2022
The vulnerability described in CVE-2016-9084 resides within the Linux kernel's vfio pci driver component, specifically in the vfio_pci_intrs.c file. This issue affects kernel versions through 4.8.11 and represents a critical flaw that can be exploited by local attackers with access to vfio PCI device files. The vulnerability stems from improper handling of memory allocation functions, creating a scenario where malicious input can lead to system instability or arbitrary code execution. The vfio (Virtual Function I/O) subsystem provides a framework for device assignment and virtualization, making it a crucial component for containerization and virtual machine environments where direct hardware access is required.
The technical flaw manifests through the misuse of the kzalloc function, which is a kernel memory allocation routine that allocates and zeros memory. In this specific case, the kernel fails to properly validate input parameters before passing them to kzalloc, leading to potential integer overflow conditions. When an attacker manipulates the input values through a vfio PCI device file, the system's memory management routines can be coerced into allocating incorrect memory sizes. This integer overflow can result in memory corruption, which may manifest as system crashes, denial of service conditions, or potentially more severe impacts depending on the execution context. The vulnerability is particularly dangerous because it operates at the kernel level, bypassing user-space protections and directly affecting system stability.
The operational impact of this vulnerability extends beyond simple denial of service, as it can potentially enable privilege escalation or arbitrary code execution within the kernel space. Local attackers who have access to a vfio PCI device file can leverage this flaw to disrupt system operations or gain elevated privileges. The vulnerability affects systems that utilize vfio for device assignment, including virtualization platforms, container environments, and systems running containerized applications that require direct hardware access. This makes the impact significant for cloud providers, enterprise environments, and any infrastructure relying on virtualization technologies where the vfio subsystem is actively used. The integer overflow condition can cause unpredictable behavior in memory management, potentially leading to memory corruption that could be exploited for more sophisticated attacks.
Mitigation strategies for CVE-2016-9084 require immediate kernel updates to versions that contain the patched vfio_pci_intrs.c implementation. Organizations should prioritize patching systems running kernel versions 4.8.11 or earlier, particularly those utilizing vfio PCI device functionality. System administrators should also implement monitoring for unauthorized access to vfio device files and consider restricting access to these files through proper file system permissions and access controls. The vulnerability aligns with CWE-190, which describes integer overflow and underflow conditions, and may map to ATT&CK techniques involving privilege escalation and system resource exhaustion. Additional defensive measures include implementing proper input validation at kernel boundaries, conducting regular security assessments of kernel modules, and maintaining up-to-date security patches across all system components that interface with hardware virtualization frameworks.