CVE-2017-8067 in Linux
Summary
by MITRE
drivers/char/virtio_console.c in the Linux kernel 4.9.x and 4.10.x before 4.10.12 interacts incorrectly with the CONFIG_VMAP_STACK option, which allows local users to cause a denial of service (system crash or memory corruption) or possibly have unspecified other impact by leveraging use of more than one virtual page for a DMA scatterlist.
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Analysis
by VulDB Data Team • 12/02/2022
The vulnerability described in CVE-2017-8067 resides within the Linux kernel's virtio console driver implementation in the file drivers/char/virtio_console.c. This issue affects kernel versions 4.9.x and 4.10.x prior to 4.10.12 and specifically manifests when the CONFIG_VMAP_STACK option is enabled. The vulnerability represents a critical flaw in kernel memory management and device driver interaction patterns that can be exploited by local attackers to compromise system stability and potentially achieve more severe outcomes.
The technical root cause of this vulnerability stems from improper handling of DMA scatterlists when multiple virtual pages are utilized in conjunction with the vmap stack feature. When CONFIG_VMAP_STACK is enabled, the kernel maps virtual memory areas differently than the standard approach, creating a scenario where the virtio console driver fails to correctly account for memory page boundaries in its DMA operations. This mismanagement occurs because the driver does not properly validate or handle the case where a single DMA scatterlist entry spans multiple virtual pages, leading to incorrect memory access patterns and potential memory corruption.
The operational impact of this vulnerability is significant as it provides local attackers with the ability to trigger either system crashes or memory corruption conditions that can result in complete system instability. The denial of service aspect means that legitimate system operations can be disrupted through carefully crafted DMA operations that exploit the flawed memory handling. Additionally, the unspecified other impacts suggest potential for more sophisticated exploitation scenarios that could extend beyond simple denial of service to include privilege escalation or information disclosure, making this vulnerability particularly dangerous in multi-user environments.
This vulnerability aligns with CWE-121, which addresses stack-based buffer overflow conditions, and CWE-122, which covers heap-based buffer overflow conditions, as the memory corruption occurs due to improper handling of virtual memory mappings. The attack pattern follows ATT&CK technique T1068, which involves local privilege escalation through exploitation of system vulnerabilities, and T1499, which encompasses network denial of service attacks that can be initiated from within the system. The exploitation requires local access to the system since the vulnerability is a kernel-level memory management issue that cannot be triggered remotely.
Mitigation strategies for this vulnerability include immediate patching of affected kernel versions to 4.10.12 or later, where the fix properly handles the interaction between virtio console operations and vmap stack functionality. System administrators should also consider disabling CONFIG_VMAP_STACK if the functionality is not required, as this would eliminate the attack surface entirely. Additionally, monitoring systems should be implemented to detect unusual memory access patterns that might indicate exploitation attempts. The patch addresses the core issue by ensuring that DMA scatterlist operations correctly handle multi-page virtual memory mappings, preventing the memory corruption scenarios that lead to system crashes or potential privilege escalation opportunities.