CVE-2017-8063 in Linux
Summary
by MITRE
drivers/media/usb/dvb-usb/cxusb.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 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 identified as CVE-2017-8063 resides within the Linux kernel's digital video broadcasting over usb subsystem specifically in the cxusb driver component located at drivers/media/usb/dvb-usb/cxusb.c. This flaw affects kernel versions 4.9.x and 4.10.x prior to the 4.10.12 release and represents a critical issue that can be exploited by local attackers to compromise system stability. The vulnerability stems from improper handling of memory management when the CONFIG_VMAP_STACK configuration option is enabled, creating a dangerous interaction that can lead to system-wide failures.
The technical root cause involves the incorrect interaction between the cxusb driver and the virtual memory management system when CONFIG_VMAP_STACK is active. When this configuration option is enabled, the kernel uses virtual memory mapping for stack allocation across multiple pages. The cxusb driver fails to properly account for this virtual page structure when managing DMA scatterlists, which are data structures used to describe memory regions for direct memory access operations. This mismanagement occurs specifically when the driver attempts to handle multiple virtual pages within a single DMA operation, leading to memory corruption and system instability.
The operational impact of this vulnerability manifests as either a denial of service condition causing system crashes or potentially more severe consequences including arbitrary code execution. Local attackers can exploit this weakness by triggering the specific code path that involves DMA scatterlist operations with virtual memory pages, effectively causing the kernel to crash and potentially leading to a complete system halt. The vulnerability's severity is amplified by its location within the kernel's core media subsystem, which is frequently accessed by legitimate system processes and user-space applications, making exploitation relatively straightforward and impactful.
This vulnerability maps to CWE-121 in the Common Weakness Enumeration catalog, specifically addressing heap-based buffer overflow conditions that occur when memory management operations are improperly handled. The attack vector aligns with ATT&CK technique T1068 which covers "Exploitation for Privilege Escalation" and T1499 which covers "Network Denial of Service" as the primary exploitation methods can lead to system crashes and availability disruption. The flaw represents a classic case of improper memory management in kernel space, where virtual memory handling conflicts with hardware-specific driver operations, creating a dangerous condition that can be leveraged by any local user with minimal privileges.
Mitigation strategies for CVE-2017-8063 require immediate kernel version updates to 4.10.12 or later where the vulnerability has been patched. System administrators should also consider disabling the CONFIG_VMAP_STACK option if the system does not require the virtual memory mapping functionality for stack allocation, though this may impact system performance and memory utilization. Additionally, monitoring for unusual kernel crashes or system instability in the media subsystem should be implemented, as these could indicate exploitation attempts. Regular kernel updates and security assessments remain crucial for maintaining system integrity, particularly given the widespread use of Linux-based systems in both enterprise and consumer environments where such vulnerabilities can have cascading effects across multiple platforms and applications.