CVE-2022-1247: Linux Kernel Race Condition Vulnerability

CVE-2022-1247 Overview

A race condition vulnerability exists in the Linux kernel's ROSE (Radio Operators Standard Environment) amateur radio protocol driver. The vulnerability is found in the rose_connect() function where improper synchronization leads to a race condition. The ROSE driver uses rose_neigh->use to represent how many objects are using the rose_neigh structure. When a user attempts to delete a rose_route via rose_ioctl(), the driver calls rose_del_node() and removes neighbours only if their "count" and "use" values are zero. This creates a Time-of-Check Time-of-Use (TOCTOU) race condition that can be exploited by a local attacker.

Critical Impact

A local attacker with low privileges can exploit this race condition to potentially gain elevated privileges, corrupt memory, or cause system instability leading to complete system compromise.

Affected Products

• Linux Linux Kernel (all versions with ROSE protocol support)
• Red Hat Enterprise Linux 9.0
• Fedora 36

Discovery Timeline

• 2022-08-31 - CVE CVE-2022-1247 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2022-1247

Vulnerability Analysis

This vulnerability is classified as CWE-362 (Concurrent Execution using Shared Resource with Improper Synchronization), commonly known as a race condition. The flaw exists in the ROSE amateur radio network protocol implementation within the Linux kernel.

The core issue lies in how the ROSE driver manages reference counting for neighbor structures. The rose_neigh->use counter tracks active users of neighbor objects, but the check-and-delete operation is not atomic. When rose_ioctl() processes a delete request, it verifies the reference counts before removal, but another thread can increment the counter between the check and the actual deletion, leading to a use-after-free condition.

Since this requires local access and specific timing conditions to trigger, successful exploitation demands precise race window manipulation. However, if successfully exploited, an attacker could achieve arbitrary code execution with kernel privileges, potentially compromising system confidentiality, integrity, and availability.

Root Cause

The root cause is the lack of proper synchronization primitives (such as spinlocks or mutex locks) protecting the critical section where the rose_neigh reference count is checked and the neighbor structure is subsequently deleted. The rose_del_node() function checks if both "count" and "use" are zero before freeing the neighbor structure, but without holding an appropriate lock during this operation, another concurrent execution path in rose_connect() can modify these values, creating a TOCTOU vulnerability.

Attack Vector

The attack requires local access to the system with low privileges. An attacker needs the ability to interact with the ROSE network protocol subsystem, which is typically available to users with appropriate permissions or CAP_NET_ADMIN capabilities.

The exploitation technique involves:

1. Creating a legitimate ROSE connection to increment the neighbor reference count
2. Simultaneously issuing a delete command via rose_ioctl()
3. Timing the operations so the deletion check passes while the reference is still in use
4. After deletion, the first operation continues to use the freed memory structure

Successful exploitation results in a use-after-free condition, which can be leveraged for privilege escalation or denial of service. The technique requires precise timing but is achievable with repeated attempts on multi-processor systems. Technical details are available in the Red Hat Bug Report #2066799.

Detection Methods for CVE-2022-1247

Indicators of Compromise

• Unexpected kernel panics or crashes related to the ROSE network subsystem
• Suspicious processes interacting with ROSE protocol interfaces (/dev/rose* devices)
• Unusual system calls targeting ROSE ioctl operations from unprivileged user accounts
• Memory corruption signatures in kernel logs referencing rose_neigh or rose_connect structures

Detection Strategies

• Monitor for processes loading or interacting with the rose kernel module
• Implement auditd rules to track ioctl() system calls on ROSE-related file descriptors
• Use kernel live patching detection tools to identify unpatched systems
• Deploy SentinelOne Singularity Platform for real-time kernel-level threat detection and behavioral analysis

Monitoring Recommendations

• Enable kernel audit logging for network subsystem operations
• Monitor dmesg and system logs for ROSE driver warnings or errors
• Track loading/unloading of the rose.ko kernel module
• Implement file integrity monitoring on kernel modules directory

How to Mitigate CVE-2022-1247

Immediate Actions Required

• Apply the latest kernel security updates from your distribution vendor
• If ROSE protocol is not needed, disable or blacklist the rose kernel module
• Restrict access to ROSE network interfaces using appropriate permissions
• Consider enabling kernel security features such as KASLR and SMEP/SMAP

Patch Information

Security patches addressing this race condition are available from major Linux distribution vendors. Red Hat has published an advisory with remediation guidance at the Red Hat CVE-2022-1247 Advisory. Administrators should update to the latest kernel version provided by their distribution that includes the fix for this vulnerability.

Workarounds

• Blacklist the ROSE kernel module by adding blacklist rose to /etc/modprobe.d/blacklist.conf
• Unload the ROSE module if currently loaded using rmmod rose
• Restrict module loading capabilities to prevent re-loading of the vulnerable module
• Apply network namespace isolation to limit access to ROSE interfaces

# Disable the ROSE kernel module (workaround)
echo "blacklist rose" >> /etc/modprobe.d/blacklist-rose.conf
echo "install rose /bin/true" >> /etc/modprobe.d/blacklist-rose.conf

# Remove the module if currently loaded
rmmod rose 2>/dev/null || true

# Regenerate initramfs to persist changes
dracut -f  # For RHEL/Fedora
# or
update-initramfs -u  # For Debian/Ubuntu