CVE-2022-0168 Overview
A denial of service (DoS) vulnerability exists in the Linux kernel's Common Internet File System (CIFS) implementation. The flaw is located in the smb2_ioctl_query_info function within fs/cifs/smb2ops.c. Due to an incorrect return value handling from the memdup_user function, a local attacker with CAP_SYS_ADMIN privileges can trigger a system crash, resulting in complete denial of service.
Critical Impact
A local attacker with administrative privileges (CAP_SYS_ADMIN capability) can crash the entire system, causing service disruption and potential data loss from interrupted operations.
Affected Products
- Linux Kernel (all vulnerable versions)
- Red Hat Enterprise Linux 8.0
- Red Hat Enterprise Linux 9.0
Discovery Timeline
- 2022-08-26 - CVE-2022-0168 published to NVD
- 2024-11-21 - Last updated in NVD database
Technical Details for CVE-2022-0168
Vulnerability Analysis
This vulnerability is classified as CWE-476 (NULL Pointer Dereference). The flaw occurs within the CIFS file system driver, specifically in the SMB2 ioctl query information handling path. When the memdup_user function fails and returns an error, the code incorrectly handles this error condition, leading to a NULL pointer dereference that triggers a kernel panic.
The vulnerability requires local access to the system and elevated privileges (CAP_SYS_ADMIN capability), which limits the attack surface but still poses a significant risk in multi-user environments or systems where privilege boundaries are critical for security isolation.
Root Cause
The root cause is improper error handling in the smb2_ioctl_query_info function. When memdup_user encounters an error (such as memory allocation failure or copy-from-user failure), it returns an error pointer rather than NULL. The vulnerable code fails to properly check for and handle this error condition, resulting in the error pointer being dereferenced as if it were a valid memory address. This causes a NULL pointer dereference, triggering a kernel panic and system crash.
Attack Vector
The attack is local in nature and requires an attacker to have CAP_SYS_ADMIN capability on the target system. The attacker can exploit this vulnerability by interacting with the CIFS file system through the ioctl interface in a manner that triggers the faulty code path in smb2_ioctl_query_info. By causing memdup_user to fail, the attacker can force the kernel to dereference an invalid pointer, resulting in a system crash.
The vulnerability mechanism involves triggering the error path in the smb2_ioctl_query_info function through malformed or specially crafted ioctl requests to mounted CIFS shares. For detailed technical analysis, refer to the Linux Kernel Commit Update which contains the patch that addresses this issue.
Detection Methods for CVE-2022-0168
Indicators of Compromise
- System crashes or kernel panics occurring during CIFS/SMB file system operations
- Kernel oops messages in system logs referencing smb2_ioctl_query_info or fs/cifs/smb2ops.c
- Unexpected reboots on systems actively using SMB/CIFS mounted shares
- Audit logs showing CAP_SYS_ADMIN ioctl operations against CIFS mounts
Detection Strategies
- Monitor kernel logs for oops messages containing references to CIFS or SMB2 functions using dmesg or journald
- Implement auditd rules to track ioctl system calls against CIFS-mounted file systems
- Deploy SentinelOne Singularity platform for real-time kernel-level threat detection and anomaly monitoring
- Review system crash dumps for evidence of NULL pointer dereference in the CIFS subsystem
Monitoring Recommendations
- Enable kernel crash dump collection (kdump) to capture forensic evidence of exploitation attempts
- Configure centralized logging for kernel messages across all affected Linux systems
- Monitor for unusual patterns of CIFS ioctl operations, especially from privileged processes
- Use SentinelOne's behavioral AI to detect anomalous privileged operations targeting file system drivers
How to Mitigate CVE-2022-0168
Immediate Actions Required
- Apply the latest kernel patches from your Linux distribution vendor
- Review and restrict CAP_SYS_ADMIN capability assignments to only essential services and users
- Consider temporarily unmounting CIFS shares on high-security systems until patches are applied
- Monitor systems for unusual crash patterns while awaiting patch deployment
Patch Information
The vulnerability has been addressed in the upstream Linux kernel. The fix is available in commit d6f5e358452479fa8a773b5c6ccc9e4ec5a20880 in the Linux kernel git repository. Red Hat has tracked this issue and provides information through Red Hat Bug Report. System administrators should update to patched kernel versions provided by their distribution vendors.
For Red Hat Enterprise Linux systems, consult the Red Hat CVE Advisory for specific remediation guidance and patched package versions.
Workarounds
- Restrict CAP_SYS_ADMIN capability to only trusted administrative accounts using capability bounding sets
- Limit access to CIFS mount points through file system permissions and SELinux/AppArmor policies
- Disable CIFS kernel module if SMB file sharing is not required: modprobe -r cifs
- Implement network segmentation to limit access to SMB servers from potentially compromised hosts
# Configuration example
# Disable CIFS module loading (if CIFS is not required)
echo "install cifs /bin/false" >> /etc/modprobe.d/disable-cifs.conf
# Remove currently loaded CIFS module
modprobe -r cifs
# Verify module is not loaded
lsmod | grep cifs
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
