CVE-2017-7346 in Linux
Summary
by MITRE
The vmw_gb_surface_define_ioctl function in drivers/gpu/drm/vmwgfx/vmwgfx_surface.c in the Linux kernel through 4.10.7 does not validate certain levels data, which allows local users to cause a denial of service (system hang) via a crafted ioctl call for a /dev/dri/renderD* device.
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Analysis
by VulDB Data Team • 08/24/2020
The vulnerability identified as CVE-2017-7346 resides within the VMware graphics driver implementation in the Linux kernel version 4.10.7 and earlier. This issue specifically affects the vmw_gb_surface_define_ioctl function located in the drivers/gpu/drm/vmwgfx/vmwgfx_surface.c file. The flaw represents a critical validation gap that enables local attackers to manipulate the graphics subsystem through improper input handling. The vulnerability impacts systems utilizing VMware graphics hardware through the Direct Rendering Infrastructure (DRI) interface, particularly affecting devices represented by /dev/dri/renderD* character devices.
The technical root cause of this vulnerability stems from insufficient validation of levels data within the vmw_gb_surface_define_ioctl function. When a local user submits a crafted ioctl call to the graphics device, the function fails to properly validate the level parameters that define surface properties in the graphics memory. This lack of input sanitization creates an exploitable condition where malformed data can be processed without proper bounds checking or parameter validation. The vulnerability manifests as a system hang or complete denial of service, effectively rendering the graphics subsystem inoperable until the system is rebooted. The flaw operates at the kernel level, making it particularly dangerous as it can be exploited by any local user with access to the graphics device.
The operational impact of this vulnerability extends beyond simple system unavailability, as it can lead to complete system instability and service disruption. Local users who can access the /dev/dri/renderD* devices can trigger the vulnerability through carefully constructed ioctl commands that manipulate the surface level parameters. The resulting system hang represents a denial of service condition that can persist until manual intervention occurs, potentially affecting system availability for legitimate users. This vulnerability particularly impacts systems running Linux kernel versions up to and including 4.10.7, making them susceptible to local privilege escalation attacks that can cause widespread disruption in multi-user environments. The issue aligns with CWE-129, which describes improper validation of input boundaries, and represents a classic example of insufficient input validation in kernel space code.
Mitigation strategies for this vulnerability require immediate kernel updates to versions 4.10.8 and later where the validation issue has been addressed through proper parameter checking. System administrators should prioritize patching affected systems, particularly those running kernel versions 4.10.7 or earlier. Additional protective measures include restricting access to the /dev/dri/renderD* devices through proper file system permissions and access controls, limiting local user privileges where possible, and implementing monitoring for suspicious ioctl activity. The vulnerability demonstrates the importance of kernel-level input validation and highlights the need for comprehensive testing of device drivers. Organizations should also consider implementing runtime protection mechanisms and regularly audit their graphics subsystem configurations. This vulnerability serves as a reminder of the critical importance of proper parameter validation in kernel space code, as identified in the ATT&CK framework under the technique of privilege escalation through kernel exploits.