CVE-2022-1462: Linux Kernel Race Condition Vulnerability

CVE-2022-1462 Overview

An out-of-bounds read vulnerability exists in the Linux kernel's TeleTYpe (TTY) subsystem. The flaw occurs when a user triggers a race condition using specific ioctl commands including TIOCSPTLCK, TIOCGPTPEER, TIOCSTI, and TCXONC, resulting in memory leakage within the flush_to_ldisc function. This race condition vulnerability allows a local attacker to crash the system or read unauthorized random data from kernel memory.

Critical Impact

Local attackers can exploit this race condition to cause system crashes (denial of service) or leak sensitive kernel memory contents, potentially exposing credentials or other privileged data.

Affected Products

• Linux Kernel (all versions prior to patch)
• Red Hat Enterprise Linux 8.0
• Red Hat Enterprise Linux 9.0
• Debian Linux 10.0

Discovery Timeline

• June 2, 2022 - CVE-2022-1462 published to NVD
• November 21, 2024 - Last updated in NVD database

Technical Details for CVE-2022-1462

Vulnerability Analysis

This vulnerability stems from improper synchronization in the Linux kernel's TTY subsystem, specifically within the line discipline (ldisc) handling code. The race condition occurs during concurrent access to TTY data structures when certain ioctl operations are invoked in rapid succession. When the flush_to_ldisc function processes data without proper locking mechanisms, it can read beyond the bounds of allocated memory buffers.

The attack requires local access to the system and involves triggering specific sequences of ioctl calls on pseudo-terminal (PTY) devices. While the attack complexity is high due to the timing requirements inherent in race conditions, successful exploitation can result in significant confidentiality and availability impacts. An attacker with low-privilege local access can potentially extract sensitive information from kernel memory or cause kernel panic conditions.

Root Cause

The root cause is a race condition (CWE-362) in the TTY subsystem's line discipline code. The vulnerability exists because the flush_to_ldisc function does not properly synchronize access to shared data structures when multiple ioctl operations (TIOCSPTLCK, TIOCGPTPEER, TIOCSTI, and TCXONC) are executed concurrently. This lack of proper locking allows one thread to access memory that another thread is in the process of modifying or freeing, leading to out-of-bounds read conditions.

Attack Vector

The attack vector is local, requiring an attacker to have user-level access to the target system. Exploitation involves:

1. Opening a pseudo-terminal pair (master/slave)
2. Rapidly issuing multiple ioctl calls in parallel threads to trigger the race condition
3. Timing the operations to hit the vulnerable window in flush_to_ldisc
4. Reading the leaked memory contents or observing system crash behavior

The vulnerability exploits the Time-of-Check Time-of-Use (TOCTOU) pattern where the state of the TTY data structures changes between validation and use. For detailed technical analysis, refer to the OSS-Sec List Analysis.

Detection Methods for CVE-2022-1462

Indicators of Compromise

• Unexpected kernel panics or system crashes, particularly with oops messages referencing TTY or ldisc functions
• Anomalous patterns of ioctl system calls targeting /dev/pts/* or /dev/tty* devices
• Processes making rapid, repeated calls to TIOCSPTLCK, TIOCGPTPEER, TIOCSTI, or TCXONC ioctls
• Memory corruption or kernel warnings in system logs related to the flush_to_ldisc function

Detection Strategies

• Deploy kernel-level monitoring to detect unusual ioctl call patterns on TTY devices
• Implement audit rules using auditd to log ioctl system calls with suspect command codes
• Monitor system logs for kernel oops or warnings mentioning TTY subsystem components
• Use SentinelOne's kernel-level behavioral analysis to detect exploitation attempts targeting race conditions

Monitoring Recommendations

• Enable kernel tracing on TTY-related functions using ftrace or perf to identify anomalous behavior
• Configure centralized logging to aggregate kernel messages across all affected systems
• Implement real-time alerting for kernel crash events that reference the flush_to_ldisc function
• Review pseudo-terminal usage patterns for unexpected high-frequency ioctl operations

How to Mitigate CVE-2022-1462

Immediate Actions Required

• Apply the latest kernel security updates from your Linux distribution vendor
• Restrict local user access to systems where possible, limiting potential attackers
• Consider implementing mandatory access control (MAC) policies using SELinux or AppArmor to restrict PTY access
• Monitor for and investigate any suspicious TTY-related activity on critical systems

Patch Information

Security patches addressing this vulnerability are available from major Linux distributions. Administrators should consult their distribution's security advisories for specific patch versions:

• Red Hat: Refer to Red Hat Bug Report ID #2078466 for patch details and affected package versions
• Debian: Security updates are documented in the Debian LTS Announcement

Ensure systems are updated to kernel versions that include the fix for the race condition in the TTY line discipline code.

Workarounds

• Limit local user access to the affected systems until patches can be applied
• Use SELinux or AppArmor policies to restrict access to pseudo-terminal devices for non-essential users
• Implement resource limits using cgroups to reduce the ability to spawn many processes needed for race condition exploitation
• Monitor and alert on unusual patterns of ioctl calls targeting TTY devices as an interim detection measure

# Example: Audit rule to monitor suspicious ioctl calls on PTY devices
# Add to /etc/audit/rules.d/tty-monitor.rules
-a always,exit -F arch=b64 -S ioctl -F path=/dev/ptmx -k tty_exploit_monitor
-a always,exit -F arch=b64 -S ioctl -F dir=/dev/pts -k tty_exploit_monitor

# Reload audit rules
auditctl -R /etc/audit/rules.d/tty-monitor.rules