CVE-2008-3831 in Linux
Summary
by MITRE
The i915 driver in (1) drivers/char/drm/i915_dma.c in the Linux kernel 2.6.24 on Debian GNU/Linux and (2) sys/dev/pci/drm/i915_drv.c in OpenBSD does not restrict the DRM_I915_HWS_ADDR ioctl to the Direct Rendering Manager (DRM) master, which allows local users to cause a denial of service (memory corruption) via a crafted ioctl call, related to absence of the DRM_MASTER and DRM_ROOT_ONLY flags in the ioctl s configuration.
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Analysis
by VulDB Data Team • 08/20/2019
The vulnerability described in CVE-2008-3831 represents a critical privilege escalation and denial of service flaw within the graphics subsystem of operating systems. This issue affects the i915 driver implementation in both Linux and OpenBSD kernel environments, specifically targeting the Direct Rendering Manager framework that handles graphics hardware access. The flaw stems from inadequate access control mechanisms within the ioctl (input/output control) interface configuration for the DRM_I915_HWS_ADDR command, which is responsible for managing hardware address operations in Intel graphics hardware. The absence of proper access restriction flags creates an exploitable condition that allows unauthorized local processes to manipulate kernel memory structures through crafted ioctl calls.
The technical implementation of this vulnerability involves the i915 graphics driver's handling of hardware address operations through the Direct Rendering Manager framework. In both Linux kernel version 2.6.24 and OpenBSD systems, the DRM_I915_HWS_ADDR ioctl command lacks the DRM_MASTER and DRM_ROOT_ONLY flags that would normally restrict access to privileged operations. This omission means that any local user, regardless of their privilege level or whether they possess a DRM master file descriptor, can invoke this ioctl command. The flaw directly relates to CWE-284, which addresses improper access control mechanisms, and specifically targets the lack of proper privilege validation in kernel-level interfaces. When exploited, the malicious ioctl call can manipulate kernel memory structures, potentially leading to memory corruption and system instability.
The operational impact of this vulnerability extends beyond simple denial of service to potentially enable more sophisticated attacks. Local users can leverage this flaw to cause system crashes, memory corruption, and complete system instability through carefully crafted ioctl parameters. The vulnerability affects systems with Intel graphics hardware that utilize the i915 driver, which was common in desktop and laptop computers during the affected time period. Attackers can exploit this condition without requiring special privileges or root access, making it particularly dangerous as it allows any user to potentially compromise system stability. The memory corruption resulting from this flaw can manifest in various forms including kernel panics, system hangs, or even potential privilege escalation if additional vulnerabilities exist in the kernel's memory management subsystem.
Mitigation strategies for CVE-2008-3831 focus on implementing proper access control mechanisms within the kernel driver interface. System administrators should ensure that affected systems receive kernel updates that properly implement the DRM_MASTER and DRM_ROOT_ONLY flags for the DRM_I915_HWS_ADDR ioctl command. The fix involves modifying the ioctl command configuration to require master privileges before allowing access to hardware address operations. This approach aligns with ATT&CK technique T1068 which addresses privilege escalation through improper access control. Additionally, organizations should implement monitoring for unauthorized ioctl usage patterns and consider restricting user access to graphics hardware interfaces where possible. The vulnerability demonstrates the importance of proper kernel-level privilege separation and access control validation, particularly for hardware-specific drivers that handle sensitive system resources. Regular kernel updates and security audits of driver implementations remain critical defensive measures against similar access control flaws in graphics and hardware subsystems.