CVE-2024-26930: Linux Kernel Use-After-Free Vulnerability

CVE-2024-26930 Overview

CVE-2024-26930 is a double free vulnerability in the Linux kernel's qla2xxx SCSI driver. The vulnerability was identified through a Coverity scan which detected a potential risk of double freeing the ha->vp_map pointer. Specifically, the pointer was freed in qla2x00_mem_alloc() and subsequently freed again in qla2x00_mem_free(ha), creating a classic double free memory corruption condition.

Critical Impact
Local attackers with low privileges can exploit this double free vulnerability to potentially achieve high impact on confidentiality, integrity, and availability of affected Linux systems running the qla2xxx SCSI driver.

Affected Products

Linux Kernel (multiple versions)
Linux Kernel 6.9-rc1
Systems utilizing QLogic qla2xxx Fibre Channel HBA drivers

Discovery Timeline

2024-05-01 - CVE-2024-26930 published to NVD
2025-03-07 - Last updated in NVD database

Technical Details for CVE-2024-26930

Vulnerability Analysis

This vulnerability is classified as CWE-415 (Double Free), a memory corruption flaw that occurs when the same memory allocation is freed more than once. In the context of the qla2xxx driver, the ha->vp_map pointer undergoes improper memory management where it gets deallocated in the qla2x00_mem_alloc() function during an error handling path, and then deallocated again in qla2x00_mem_free(ha) during cleanup operations.

Double free vulnerabilities can lead to heap corruption, which may result in arbitrary code execution, denial of service through crashes, or other unpredictable behavior. The local attack vector requires an attacker to have existing access to the system with low-level privileges, but successful exploitation could elevate their capabilities significantly.

Root Cause

The root cause stems from inadequate pointer management in the qla2xxx driver's memory allocation and deallocation routines. When qla2x00_mem_alloc() encounters an error condition and frees ha->vp_map, it fails to set the pointer to NULL. Subsequently, when qla2x00_mem_free(ha) executes during cleanup, it attempts to free the same already-freed memory allocation because it has no way to determine the memory was previously deallocated.

Attack Vector

The vulnerability requires local access to the system with low privileges. An attacker could potentially trigger the vulnerable code path by manipulating SCSI driver operations or causing error conditions that lead to the memory management functions being called in a sequence that triggers the double free. The attack does not require user interaction.

The fix involves assigning NULL to the vp_map pointer after freeing it, as kfree() safely handles NULL pointers without performing any operation. This is a standard defensive programming practice to prevent double free vulnerabilities.

Detection Methods for CVE-2024-26930

Indicators of Compromise

Unexpected kernel panics or crashes related to the qla2xxx driver
Memory corruption errors in kernel logs involving heap operations
System instability on servers with QLogic Fibre Channel HBAs
Unusual kernel oops messages referencing qla2x00_mem_alloc or qla2x00_mem_free functions

Detection Strategies

Monitor kernel logs (dmesg, /var/log/kern.log) for qla2xxx driver errors or memory-related warnings
Implement kernel debugging tools such as KASAN (Kernel Address Sanitizer) to detect double free conditions
Use system monitoring to detect unexpected driver behavior or crashes
Review loaded kernel modules and verify qla2xxx driver version against patched releases

Monitoring Recommendations

Enable kernel audit logging for driver-related events
Configure alerting for kernel panic events and qla2xxx driver exceptions
Monitor system stability metrics on servers with QLogic HBAs
Implement centralized log collection to correlate potential exploitation attempts across infrastructure

How to Mitigate CVE-2024-26930

Immediate Actions Required

Update the Linux kernel to a patched version that includes the security fix
Review systems with QLogic qla2xxx Fibre Channel HBAs for vulnerability exposure
Prioritize patching on critical systems with local user access
Restrict local access to trusted users on vulnerable systems until patches are applied

Patch Information

The vulnerability has been addressed through multiple kernel patches that assign NULL to the vp_map pointer after freeing to prevent the double free condition. The following patches are available:

Workarounds

Limit local access to systems running vulnerable kernel versions
Consider disabling the qla2xxx driver module if QLogic Fibre Channel functionality is not required
Implement strict access controls to prevent untrusted users from triggering driver operations
Monitor systems for signs of exploitation while awaiting kernel updates

bash

# Check current kernel version and qla2xxx driver status
uname -r
lsmod | grep qla2xxx

# If qla2xxx is not needed, it can be blacklisted temporarily
echo "blacklist qla2xxx" >> /etc/modprobe.d/blacklist-qla2xxx.conf