CVE-2023-50431: Linux Kernel Information Disclosure Flaw

CVE-2023-50431 Overview

CVE-2023-50431 is an information leakage vulnerability affecting the Linux kernel's HabanaLabs accelerator driver. The vulnerability exists in the sec_attest_info function within drivers/accel/habanalabs/common/habanalabs_ioctl.c, where the info->pad0 structure member is not properly initialized before being copied to user space. This uninitialized memory condition allows local attackers with low privileges to potentially access sensitive kernel memory contents.

Critical Impact

Local attackers can exploit uninitialized memory in the HabanaLabs driver to leak sensitive kernel information, potentially exposing memory addresses or other confidential data that could facilitate further attacks.

Affected Products

• Linux Kernel through version 6.6.5
• Systems with HabanaLabs accelerator hardware and drivers
• Any Linux distribution running vulnerable kernel versions with the HabanaLabs driver enabled

Discovery Timeline

• 2023-11 - Vulnerability disclosed on the Freedesktop DRI Development Discussion
• 2023-12-09 - CVE CVE-2023-50431 published to NVD
• 2025-05-30 - Last updated in NVD database

Technical Details for CVE-2023-50431

Vulnerability Analysis

This vulnerability is classified as an Uninitialized Memory Use flaw, which falls under the broader category of Memory Information Disclosure vulnerabilities. The issue arises from improper handling of structure padding in the HabanaLabs ioctl interface.

When the sec_attest_info function processes security attestation requests, it allocates a structure containing padding bytes (pad0). These padding bytes are not explicitly initialized before the entire structure is copied back to user space via the ioctl interface. As a result, whatever data previously occupied that memory location—potentially including sensitive kernel pointers, stack data, or other confidential information—can be read by an unprivileged local user.

The attack requires local access and low privileges, meaning an attacker must already have some level of access to the system. However, no user interaction is required to exploit this vulnerability.

Root Cause

The root cause is a failure to initialize the pad0 member within the info structure in the sec_attest_info function. In C, structure members that are not explicitly initialized may contain arbitrary data from previous memory allocations. When this uninitialized data is subsequently copied to user space without sanitization, it creates an information disclosure channel. The fix involves explicitly zeroing or initializing the padding field before the structure is returned to the user.

Attack Vector

The attack vector is local, requiring the attacker to have access to the target system with sufficient privileges to interact with the HabanaLabs device driver through ioctl calls. The attacker would craft specific ioctl requests to the HabanaLabs driver that trigger the vulnerable code path, then read the response to extract leaked kernel memory contents.

The exploitation flow involves:

1. Opening the HabanaLabs device file
2. Issuing the appropriate ioctl command that invokes sec_attest_info
3. Reading the returned structure, including the uninitialized pad0 field
4. Analyzing the leaked data for sensitive information such as kernel addresses

Since no verified proof-of-concept code is available, the vulnerability mechanism involves standard ioctl interaction with the HabanaLabs driver. Technical details about the specific ioctl command and structure layout can be found in the Linux Kernel Commit Update.

Detection Methods for CVE-2023-50431

Indicators of Compromise

• Unusual frequency of ioctl calls to HabanaLabs device files (/dev/hl*)
• Processes with no legitimate need accessing HabanaLabs accelerator devices
• Repeated security attestation requests from non-authorized applications
• Memory access patterns indicating information harvesting attempts

Detection Strategies

• Monitor system calls for ioctl operations targeting HabanaLabs devices from unexpected processes
• Implement audit rules using auditd to track access to /dev/hl* device files
• Deploy endpoint detection and response (EDR) solutions capable of monitoring kernel driver interactions
• Review application whitelists for processes legitimately requiring HabanaLabs driver access

Monitoring Recommendations

• Configure SentinelOne agents to monitor for suspicious ioctl patterns against accelerator devices
• Enable kernel auditing for device file access to HabanaLabs hardware
• Implement file integrity monitoring on kernel modules and driver configurations
• Set up alerts for new processes accessing HabanaLabs devices outside normal operational patterns

How to Mitigate CVE-2023-50431

Immediate Actions Required

• Update the Linux kernel to a patched version that includes commit a9f07790a4b2250f0140e9a61c7f842fd9b618c7
• Restrict access to HabanaLabs device files using appropriate file permissions
• Implement device access controls using udev rules to limit which users can interact with the hardware
• Review and audit processes with access to HabanaLabs accelerator devices

Patch Information

The vulnerability has been addressed in the Linux kernel through commit a9f07790a4b2250f0140e9a61c7f842fd9b618c7. This patch ensures that the pad0 field is properly initialized before the structure is copied to user space, preventing the information leak.

For detailed patch information, refer to the Linux Kernel Commit Update.

Workarounds

• Restrict device file permissions to limit access to HabanaLabs devices to only necessary users and processes
• Use mandatory access control systems (SELinux, AppArmor) to confine processes that interact with the driver
• Remove or blacklist the HabanaLabs kernel module if not required for system operation
• Implement network segmentation to limit lateral movement if kernel information is leaked

# Configuration example - Restrict HabanaLabs device access
# Create udev rule to limit device permissions
echo 'SUBSYSTEM=="accel", KERNEL=="hl*", MODE="0600", OWNER="root", GROUP="root"' | sudo tee /etc/udev/rules.d/99-habanalabs-restrict.rules

# Reload udev rules
sudo udevadm control --reload-rules
sudo udevadm trigger

# Optionally blacklist the module if not needed
echo "blacklist habanalabs" | sudo tee /etc/modprobe.d/blacklist-habanalabs.conf