CVE-2017-8062 in Linux
Summary
by MITRE
drivers/media/usb/dvb-usb/dw2102.c in the Linux kernel 4.9.x and 4.10.x before 4.10.4 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 identified as CVE-2017-8062 resides within the Linux kernel's digital video broadcasting over usb subsystem, specifically in the dw2102.c driver file that manages certain usb dvb devices. This flaw manifests in kernel versions 4.9.x and 4.10.x prior to 4.10.4, where the driver fails to properly handle memory management when the CONFIG_VMAP_STACK configuration option is enabled. The issue occurs during the processing of dma scatterlists which are used to describe non-contiguous memory regions for usb data transfers. When the kernel employs virtual memory mapping for stack allocation through vmap stack functionality, the driver's interaction with these memory structures becomes problematic.
The technical root cause of this vulnerability stems from improper handling of memory descriptors when multiple virtual pages are required for a single dma scatterlist entry. The dw2102 driver does not correctly account for the virtual memory layout when the kernel uses vmap stack, leading to potential memory corruption or system crashes. This occurs because the driver assumes a flat memory model where physical and virtual addresses map directly, but vmap stack creates a more complex virtual memory arrangement that breaks this assumption. The vulnerability specifically affects the way the driver processes scatterlist entries that span multiple virtual pages, causing memory management inconsistencies that can result in kernel panics or data corruption.
The operational impact of this vulnerability presents significant risks to systems running affected kernel versions, particularly those utilizing usb dvb devices such as digital television receivers or satellite tuners. Local attackers with access to the system can exploit this weakness to either cause a denial of service through system crashes or potentially achieve more severe memory corruption that could lead to privilege escalation or arbitrary code execution. The vulnerability is particularly concerning because it operates at the kernel level where memory corruption can have cascading effects throughout the operating system. The use of CONFIG_VMAP_STACK, which is designed to improve memory management efficiency, actually creates the conditions for this vulnerability to manifest, making it a particularly insidious issue that can affect systems without explicit awareness of the configuration.
Mitigation strategies for CVE-2017-8062 primarily involve updating to kernel versions 4.10.4 or later where the vulnerability has been addressed through proper handling of virtual memory mappings in the dw2102 driver. System administrators should also consider disabling the CONFIG_VMAP_STACK option if dvb-usb functionality is critical and immediate kernel updates are not feasible, though this may impact overall system performance. Additionally, monitoring for unusual system crashes or memory corruption patterns can help detect exploitation attempts. The vulnerability aligns with CWE-121, which covers stack-based buffer overflow conditions, and relates to ATT&CK technique T1068, which involves exploiting local privileges to gain system access. Organizations should prioritize patching this vulnerability as part of their regular security maintenance procedures to prevent potential exploitation by malicious actors who might leverage it for persistent access or system disruption.