CVE-2024-27053: Linux Kernel Race Condition Vulnerability

CVE-2024-27053 Overview

CVE-2024-27053 is a Race Condition vulnerability in the Linux kernel's wilc1000 WiFi driver. The vulnerability exists in the connect path of the cfg80211 layer, where a RCU (Read-Copy-Update) pointer is dereferenced outside of a RCU critical section. This improper RCU usage can lead to a Null Pointer Dereference condition when parsing target BSS (Base Service Set) parameters during WiFi connection attempts.

The flaw was identified through lockdep (lock debugging) analysis, which detected suspicious RCU usage in the wilc_parse_join_bss_param function. When WiFi connection requests are processed through wpa_supplicant, the driver improperly accesses RCU-protected data without holding the appropriate read lock, potentially causing system instability or denial of service.

Critical Impact

This vulnerability can be exploited over the network to cause denial of service conditions on affected Linux systems using the Microchip WILC1000 WiFi chipset, potentially disrupting wireless connectivity and system stability.

Affected Products

• Linux Kernel (multiple versions with wilc1000 driver)
• Debian Linux 10.0
• Systems using Microchip WILC1000 WiFi chipset (e.g., Atmel SAMA5)

Discovery Timeline

• 2024-05-01 - CVE CVE-2024-27053 published to NVD
• 2025-04-08 - Last updated in NVD database

Technical Details for CVE-2024-27053

Vulnerability Analysis

The vulnerability resides in the wilc_parse_join_bss_param function located in drivers/net/wireless/microchip/wilc1000/hif.c. When the cfg80211 layer initiates a WiFi connection through nl80211_connect, the code path eventually reaches wilc_parse_join_bss_param where BSS parameters are parsed from the connection request.

The core issue is that the driver dereferences a RCU-protected pointer to access Information Elements (IEs) data without first entering a RCU read-side critical section. In the Linux kernel's RCU mechanism, pointers protected by RCU must only be accessed within rcu_read_lock() and rcu_read_unlock() boundaries to ensure safe concurrent access and prevent use-after-free or null pointer dereference conditions.

The vulnerability can lead to data corruption, null pointer dereference, or use-after-free conditions if the underlying data structure is modified or freed while being accessed.

Root Cause

The root cause is improper synchronization in the wilc1000 driver's connection handling code. Specifically, the rcu_dereference_check() function is called at line 386 of hif.c without the calling thread holding the RCU read lock. This violates the RCU API contract which requires all RCU pointer dereferences to occur within RCU read-side critical sections.

The call stack demonstrates the violation originates from userspace through wpa_supplicant → sys_sendmsg → netlink_sendmsg → nl80211_connect → cfg80211_connect → connect → wilc_parse_join_bss_param, where the final function improperly accesses RCU-protected IEs data.

Attack Vector

The vulnerability is exploitable over the network without requiring authentication or user interaction. An attacker could potentially trigger this vulnerability by:

1. Manipulating WiFi beacon frames or probe responses to cause specific parsing conditions
2. Exploiting race conditions during rapid connect/disconnect cycles
3. Sending malformed 802.11 management frames that trigger the vulnerable code path

The attack targets systems running the wilc1000 driver, commonly found in embedded Linux devices using the Microchip WILC1000 WiFi chipset, including Atmel SAMA5-based hardware.

The fix involves wrapping the IEs data access within a proper RCU read critical section using rcu_read_lock() and rcu_read_unlock(), and copying the required IEs data while inside the critical section to avoid holding the lock for the entire wilc_parse_join_bss_param function execution.

Detection Methods for CVE-2024-27053

Indicators of Compromise

• Kernel warning messages containing "WARNING: suspicious RCU usage" in system logs
• Stack traces referencing wilc_parse_join_bss_param from hif.c line 386
• System instability or crashes during WiFi connection attempts on WILC1000-equipped devices
• Kernel oops or panic events involving the wilc1000 driver module

Detection Strategies

• Enable kernel lockdep debugging (CONFIG_PROVE_LOCKING=y) to detect RCU usage violations at runtime
• Monitor dmesg output for "suspicious rcu_dereference_check() usage" warnings from the wilc1000 driver
• Deploy kernel tracing to capture calls to wilc_parse_join_bss_param and associated RCU functions
• Use static analysis tools to identify RCU API violations in driver code

Monitoring Recommendations

• Configure syslog monitoring to alert on kernel warnings containing "wilc1000" and "RCU"
• Implement watchdog monitoring for system stability on affected embedded devices
• Track WiFi connection failures and system restarts correlated with wireless activity
• Monitor for unusual 802.11 management frame patterns that could indicate exploitation attempts

How to Mitigate CVE-2024-27053

Immediate Actions Required

• Update the Linux kernel to a patched version containing the security fix
• If immediate patching is not possible, consider temporarily disabling the wilc1000 driver module on affected systems
• For critical systems, evaluate using alternative WiFi hardware with different drivers
• Monitor affected systems for signs of exploitation while awaiting patch deployment

Patch Information

The Linux kernel maintainers have released patches across multiple stable kernel branches. The fix modifies the wilc_parse_join_bss_param function to properly acquire the RCU read lock before accessing the IEs data and copies the required information while holding the lock.

Official patches are available from the kernel git repository:

• Kernel Git Commit 205c503
• Kernel Git Commit 4bfd20d
• Kernel Git Commit 5800ec7
• Kernel Git Commit 745003b
• Kernel Git Commit b4bbf38
• Kernel Git Commit d80fc43
• Kernel Git Commit dd50d3e
• Kernel Git Commit e556006

For Debian Linux 10.0, refer to the Debian LTS Announcement for package updates.

Workarounds

• Blacklist the wilc1000 kernel module if WiFi functionality is not required: add blacklist wilc1000 to /etc/modprobe.d/blacklist.conf
• Use wired Ethernet connectivity as an alternative to WiFi on affected embedded devices
• Implement network segmentation to limit exposure of vulnerable devices
• Deploy intrusion detection systems to monitor for potential exploitation attempts

# Temporary workaround: Disable wilc1000 module
echo "blacklist wilc1000" | sudo tee /etc/modprobe.d/blacklist-wilc1000.conf
sudo modprobe -r wilc1000

# Verify module is unloaded
lsmod | grep wilc1000