CVE-2023-1078: Linux Kernel Privilege Escalation Flaw

CVE-2023-1078 Overview

A type confusion vulnerability has been identified in the Linux Kernel's RDS (Reliable Datagram Sockets) protocol. The flaw exists in the rds_rm_zerocopy_callback() function, which improperly uses list_entry() on the head of a list, causing a type confusion condition. This vulnerability can be triggered by a local user through the rds_message_put() function, resulting in a scenario where struct rds_msg_zcopy_info *info actually points to attacker-controlled data. Successful exploitation leads to out-of-bounds memory access and lock corruption.

Critical Impact

Local attackers with low privileges can exploit this type confusion vulnerability to achieve out-of-bounds memory access and lock corruption, potentially leading to privilege escalation or denial of service on affected Linux systems.

Affected Products

• Linux Kernel (multiple versions)
• Debian Linux (LTS versions)
• NetApp products using affected Linux Kernel versions

Discovery Timeline

• 2023-03-27 - CVE-2023-1078 published to NVD
• 2025-05-05 - Last updated in NVD database

Technical Details for CVE-2023-1078

Vulnerability Analysis

This vulnerability represents a classic type confusion issue (CWE-843) combined with out-of-bounds write capabilities (CWE-787) within the Linux Kernel's RDS protocol implementation. The RDS protocol is designed to provide reliable, in-order datagram delivery and is commonly used in Oracle database clustering environments.

The core issue lies in the improper handling of list structures within the zero-copy callback mechanism. When the rds_rm_zerocopy_callback() function processes messages, it uses the list_entry() macro on the head of a list rather than on a valid list element. This causes the function to interpret arbitrary memory as a struct rds_msg_zcopy_info structure, leading to type confusion.

The vulnerability requires local access and low privileges to exploit. No user interaction is required, making it particularly concerning for multi-tenant environments or systems where local users have shell access.

Root Cause

The root cause stems from incorrect usage of the list_entry() macro in the rds_rm_zerocopy_callback() function. The Linux kernel's list implementation uses sentinel nodes (list heads) to mark the beginning and end of lists. When list_entry() is called on this sentinel node instead of an actual list element, it calculates an incorrect memory offset, causing the returned pointer to reference unintended memory.

This programming error results in the info pointer being set to a memory location that may be controlled by a local attacker, enabling exploitation through carefully crafted RDS messages.

Attack Vector

The attack requires local access to the system with low-level user privileges. An attacker can trigger the vulnerability through the following mechanism:

1. The attacker creates and configures an RDS socket
2. By sending specially crafted messages through the RDS protocol, the attacker triggers the rds_message_put() function
3. The vulnerable rds_rm_zerocopy_callback() function is invoked during message cleanup
4. The improper list_entry() usage causes type confusion, allowing the attacker to manipulate kernel memory
5. This results in out-of-bounds memory access and potential lock corruption

The vulnerability can be leveraged for privilege escalation by corrupting kernel data structures or for denial of service by triggering kernel panics through lock corruption.

Detection Methods for CVE-2023-1078

Indicators of Compromise

• Unexpected kernel panics or system crashes related to RDS protocol handling
• Abnormal lock contention or deadlock conditions in kernel logs involving RDS subsystem
• Suspicious local user activity involving RDS socket creation and message manipulation
• Kernel oops messages referencing rds_rm_zerocopy_callback or related RDS functions

Detection Strategies

• Monitor kernel logs for RDS-related error messages, particularly those involving rds_rm_zerocopy_callback or memory corruption indicators
• Implement kernel-level auditing to track RDS socket operations by non-privileged users
• Deploy endpoint detection solutions capable of monitoring kernel-level anomalies and system call patterns
• Use SentinelOne's behavioral AI to detect unusual kernel memory access patterns that may indicate exploitation attempts

Monitoring Recommendations

• Enable kernel auditing with focus on socket system calls involving AF_RDS address family
• Configure system monitoring to alert on unexpected kernel module loading or RDS protocol usage
• Implement process monitoring for applications that shouldn't normally use RDS sockets
• Review system logs regularly for signs of exploitation attempts or kernel instability

How to Mitigate CVE-2023-1078

Immediate Actions Required

• Apply the official kernel patch (commit f753a68980cf4b59a80fe677619da2b1804f526d) immediately on all affected systems
• If immediate patching is not possible, disable or unload the RDS kernel module using modprobe -r rds if not required for operations
• Restrict local user access on critical systems until patches can be applied
• Monitor systems for signs of exploitation using the detection methods outlined above

Patch Information

The Linux Kernel team has released a fix for this vulnerability. The patch is available through the Linux Kernel Commit Update which corrects the improper usage of list_entry() in the rds_rm_zerocopy_callback() function.

Distribution-specific patches are available:

• Debian LTS users should refer to the Debian LTS Announcement #1 and Debian LTS Announcement #2
• NetApp users should consult the NetApp Security Advisory

Additional technical discussion is available at the Openwall OSS-Security Discussion.

Workarounds

• Disable the RDS kernel module if not required by adding blacklist rds to /etc/modprobe.d/blacklist.conf
• Implement network segmentation to limit exposure of systems running RDS services
• Apply principle of least privilege to minimize the number of users with local system access
• Use mandatory access control systems like SELinux or AppArmor to restrict RDS socket access to authorized applications only

# Disable RDS module if not needed
echo "blacklist rds" >> /etc/modprobe.d/blacklist.conf
echo "install rds /bin/false" >> /etc/modprobe.d/blacklist.conf
# Unload the module if currently loaded
modprobe -r rds 2>/dev/null || true
# Verify module is not loaded
lsmod | grep rds