CVE-2022-2380: Linux Kernel DOS Vulnerability

CVE-2022-2380 Overview

CVE-2022-2380 is an out-of-bounds memory access vulnerability discovered in the Linux kernel's framebuffer device driver for Silicon Motion SM712 graphics chips. The vulnerability exists in the smtcfb_read() function within the drivers/video/fbdev/sm712fb.c file. This memory safety issue allows local attackers to trigger an out-of-bounds read or write operation, potentially resulting in a kernel crash and denial of service condition on affected systems.

Critical Impact

Local attackers with low privileges can exploit this vulnerability to crash the Linux kernel, causing system-wide denial of service on systems using the SM712 framebuffer driver.

Affected Products

• Linux Kernel (all vulnerable versions using the sm712fb driver)
• Systems with Silicon Motion SM712 graphics hardware utilizing the affected framebuffer driver
• Linux distributions shipping vulnerable kernel versions

Discovery Timeline

• 2022-07-13 - CVE CVE-2022-2380 published to NVD
• 2025-04-23 - Last updated in NVD database

Technical Details for CVE-2022-2380

Vulnerability Analysis

This vulnerability is classified under CWE-125 (Out-of-Bounds Read) and CWE-787 (Out-of-Bounds Write), indicating that the smtcfb_read() function fails to properly validate memory boundaries when processing framebuffer data. The SM712 framebuffer driver (sm712fb) is a legacy driver used for Silicon Motion graphics chips, commonly found in older embedded systems and thin clients.

The vulnerability requires local access to exploit, meaning an attacker must have some level of system access to trigger the condition. While exploitation does not require user interaction and can be performed with low privileges, the impact is limited to availability—causing a kernel panic or system crash without direct data confidentiality or integrity compromise.

Root Cause

The root cause of CVE-2022-2380 lies in improper bounds checking within the smtcfb_read() function. When reading framebuffer memory, the function does not adequately validate that the requested memory region falls within the allocated buffer boundaries. This allows a malicious local user to craft requests that access memory outside the intended framebuffer region, triggering an out-of-bounds memory access condition that can destabilize the kernel.

Attack Vector

The attack vector for this vulnerability is local, requiring the attacker to have authenticated access to the target system. The exploitation path involves:

1. The attacker gains local access to a Linux system running the vulnerable sm712fb driver
2. The attacker interacts with the framebuffer device (typically /dev/fb0 or similar)
3. By sending specially crafted read requests to the framebuffer device, the attacker triggers the out-of-bounds memory access in smtcfb_read()
4. The kernel encounters an invalid memory access, resulting in a crash or panic

The vulnerability exists in the data processing path of the framebuffer read operation. For technical details on the specific code changes, refer to the Linux Kernel Commit that addresses this issue.

Detection Methods for CVE-2022-2380

Indicators of Compromise

• Kernel panic messages or crash logs referencing the smtcfb_read function or sm712fb.c driver
• Unexpected system reboots or hangs on systems using SM712 graphics hardware
• Entries in kernel logs (dmesg) showing memory access violations in the framebuffer subsystem
• Failed integrity checks on the sm712fb kernel module

Detection Strategies

• Monitor kernel logs for BUG or OOPS messages associated with the sm712fb driver
• Implement system auditing to track access to framebuffer devices (/dev/fb*)
• Use kernel debugging tools such as KASAN (Kernel Address SANitizer) to detect out-of-bounds memory accesses in development environments
• Deploy endpoint detection and response (EDR) solutions capable of monitoring kernel-level anomalies

Monitoring Recommendations

• Configure centralized logging to capture kernel panic and crash events across the infrastructure
• Establish baseline behavior for framebuffer device access and alert on anomalous patterns
• Implement file integrity monitoring on kernel modules, particularly the sm712fb driver
• Use SentinelOne Singularity platform to monitor for kernel-level exploits and system stability issues

How to Mitigate CVE-2022-2380

Immediate Actions Required

• Update the Linux kernel to a patched version that includes the fix (commit bd771cf5c4254511cc4abb88f3dab3bd58bdf8e8)
• If patching is not immediately possible, consider blacklisting the sm712fb module if the SM712 hardware is not required
• Restrict access to framebuffer devices by configuring appropriate file permissions
• Limit local access to affected systems to trusted users only

Patch Information

The vulnerability has been addressed in the Linux kernel through commit bd771cf5c4254511cc4abb88f3dab3bd58bdf8e8 in the linux-fbdev git repository. The patch adds proper boundary validation to the smtcfb_read() function, ensuring that memory accesses remain within the allocated framebuffer region. System administrators should update to kernel versions that include this fix or apply the patch manually if using custom kernel builds.

Refer to the Linux Kernel Commit for the complete patch details.

Workarounds

• Blacklist the sm712fb kernel module if SM712 graphics hardware is not in use by adding blacklist sm712fb to /etc/modprobe.d/blacklist.conf
• Restrict framebuffer device permissions to prevent unprivileged users from accessing /dev/fb* devices
• Implement mandatory access control (SELinux/AppArmor) policies to limit which processes can interact with framebuffer devices
• Consider migrating affected systems to alternative display drivers if available

# Blacklist the vulnerable sm712fb module if not required
echo "blacklist sm712fb" | sudo tee /etc/modprobe.d/blacklist-sm712fb.conf
sudo update-initramfs -u

# Restrict framebuffer device permissions
sudo chmod 600 /dev/fb*