CVE-2022-0494: Linux Kernel Information Disclosure Flaw

CVE-2022-0494 Overview

A kernel information leak vulnerability was discovered in the scsi_ioctl function located in drivers/scsi/scsi_ioctl.c within the Linux kernel. This flaw enables a local attacker who possesses special user privileges (specifically CAP_SYS_ADMIN or CAP_SYS_RAWIO capabilities) to extract sensitive kernel memory information, creating potential confidentiality issues.

Critical Impact

Privileged local attackers can leverage this information disclosure vulnerability to leak sensitive kernel memory contents, potentially exposing kernel addresses or other security-sensitive data that could aid in further exploitation attempts.

Affected Products

• Linux Kernel versions prior to 5.17 (including release candidates 5.17-rc1 through 5.17-rc4)
• Debian Linux 9.0 (Stretch)
• Debian Linux 10.0 (Buster)
• Debian Linux 11.0 (Bullseye)

Discovery Timeline

• 2022-03-25 - CVE-2022-0494 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2022-0494

Vulnerability Analysis

This vulnerability represents an information disclosure flaw within the Linux kernel's SCSI subsystem. The issue stems from improper handling of memory in the scsi_ioctl function, which processes SCSI generic ioctl commands. When a privileged user invokes specific SCSI ioctl operations, the kernel may inadvertently expose uninitialized memory contents back to userspace.

The vulnerability is classified under CWE-200 (Exposure of Sensitive Information to an Unauthorized Actor) and CWE-908 (Use of Uninitialized Resource), indicating that the root cause involves uninitialized memory being returned to the caller without proper sanitization.

While the attack requires local access and elevated privileges (CAP_SYS_ADMIN or CAP_SYS_RAWIO), successful exploitation can compromise the confidentiality of kernel memory. This type of information leak is particularly concerning as it may reveal kernel address space layout information (KASLR bypass), cryptographic keys, or other sensitive data resident in kernel memory.

Root Cause

The vulnerability originates from improper initialization of memory buffers within the scsi_ioctl function in drivers/scsi/scsi_ioctl.c. When handling certain SCSI ioctl requests, the function fails to properly zero or initialize memory structures before copying them back to userspace. This results in stale or uninitialized kernel memory contents being exposed to the calling process.

The use of uninitialized resources (CWE-908) combined with the subsequent information exposure (CWE-200) creates a scenario where privileged attackers can systematically extract kernel memory information through repeated ioctl calls.

Attack Vector

The attack requires local access to the system and specific Linux capabilities (CAP_SYS_ADMIN or CAP_SYS_RAWIO). An attacker with these privileges can:

1. Open a SCSI device file (typically /dev/sg* or similar)
2. Issue specially crafted ioctl calls to the device
3. Read the response buffers which may contain uninitialized kernel memory
4. Analyze the leaked data for sensitive information such as kernel pointers or memory layout details

The vulnerability is exploited through standard SCSI generic ioctl interfaces. While the privilege requirements limit the attack surface, compromised services running with SCSI device access or containerized environments with raw device access could be targeted. The leaked information could facilitate additional attacks such as KASLR bypasses or privilege escalation exploits.

Detection Methods for CVE-2022-0494

Indicators of Compromise

• Unusual or excessive ioctl system calls to SCSI device files (/dev/sg*, /dev/sd*)
• Processes with CAP_SYS_ADMIN or CAP_SYS_RAWIO capabilities making repeated SCSI generic device operations
• Suspicious access patterns to SCSI generic device nodes from non-standard processes

Detection Strategies

• Monitor system call activity for ioctl operations targeting SCSI device files, particularly from unexpected processes
• Implement audit rules using auditd to track access to /dev/sg* devices and SG_IO ioctl requests
• Deploy kernel-level monitoring to detect patterns consistent with information leak exploitation attempts
• Use SentinelOne Singularity platform to identify anomalous kernel-level activity and suspicious process behaviors

Monitoring Recommendations

• Configure audit logging for all SCSI device access using Linux Audit Framework (auditctl)
• Monitor for processes acquiring CAP_SYS_ADMIN or CAP_SYS_RAWIO capabilities unexpectedly
• Review kernel logs for SCSI subsystem errors or anomalies that may indicate exploitation attempts
• Implement file integrity monitoring on SCSI device nodes to detect unauthorized access patterns

How to Mitigate CVE-2022-0494

Immediate Actions Required

• Update affected Linux kernel installations to patched versions (5.17 or later with the fix applied)
• Apply vendor-specific security updates from Debian or your Linux distribution
• Review and restrict CAP_SYS_ADMIN and CAP_SYS_RAWIO capabilities to only essential processes
• Audit systems to identify processes with unnecessary SCSI device access permissions

Patch Information

The vulnerability has been addressed in the Linux kernel. Security advisories and patches are available from multiple sources:

• Red Hat Bug Report #2039448 - Red Hat tracking and analysis
• Kernel Mailing List Discussion - Original patch discussion
• Debian Security Advisory DSA-5161 - Debian stable security update
• Debian Security Advisory DSA-5173 - Additional Debian security update
• Debian LTS Announcement July 2022 - Debian LTS security update

Organizations should apply the appropriate kernel updates from their distribution vendor to remediate this vulnerability.

Workarounds

• Restrict access to SCSI device nodes using file permissions or ACLs to minimize the attack surface
• Remove CAP_SYS_ADMIN and CAP_SYS_RAWIO capabilities from non-essential processes using capability bounding sets
• Use container security policies to prevent raw device access where SCSI operations are not required
• Implement mandatory access control (SELinux/AppArmor) policies to limit SCSI device access to trusted applications

# Restrict SCSI generic device access
chmod 600 /dev/sg*

# Audit SCSI device access
auditctl -w /dev/sg0 -p rw -k scsi_device_access

# Drop capabilities for a process using setcap (if applicable)
setcap -r /path/to/binary