CVE-2016-6480 in Linux
Summary
by MITRE
Race condition in the ioctl_send_fib function in drivers/scsi/aacraid/commctrl.c in the Linux kernel through 4.7 allows local users to cause a denial of service (out-of-bounds access or system crash) by changing a certain size value, aka a "double fetch" vulnerability.
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Analysis
by VulDB Data Team • 09/13/2022
The vulnerability identified as CVE-2016-6480 represents a critical race condition within the Linux kernel's aacraid storage driver implementation. This flaw exists in the ioctl_send_fib function located in drivers/scsi/aacraid/commctrl.c and affects kernel versions through 4.7. The vulnerability stems from a double fetch pattern where the kernel performs the same memory access operation twice without proper synchronization, creating an exploitable window where malicious actors can manipulate system state between these two fetch operations. The race condition occurs when a local user modifies a specific size value during the ioctl operation, leading to unpredictable behavior in the kernel's memory management subsystem.
The technical implementation of this vulnerability demonstrates a classic double fetch scenario that aligns with CWE-362, which specifically addresses race conditions in concurrent programming environments. The flaw manifests when the kernel retrieves a size parameter from user space, performs validation, then later retrieves the same parameter again without revalidating, allowing an attacker to modify the value between these two operations. This pattern creates a situation where the kernel may access memory outside of the intended bounds or attempt operations on invalid data structures, resulting in either memory corruption or system crashes that manifest as kernel oops or system panics.
From an operational impact perspective, this vulnerability provides local users with the ability to execute denial of service attacks against the target system, potentially causing complete system crashes or rendering the storage subsystem unavailable. The attack vector requires local access to the system, making it less severe than remote exploits but still highly concerning for systems where local privilege escalation is possible or where the target system is expected to maintain high availability. The vulnerability affects systems using the aacraid SCSI controller drivers, which are commonly found in enterprise storage solutions and server environments where kernel stability is paramount. The impact extends beyond simple service disruption as kernel crashes can lead to data loss, unavailability of critical storage services, and potential compromise of the entire system if the crash occurs during critical operations.
Mitigation strategies for CVE-2016-6480 should focus on both immediate patching and system hardening measures. The primary solution involves upgrading to a Linux kernel version that contains the fix for this race condition, typically kernel 4.8 or later where the double fetch vulnerability has been addressed through proper synchronization mechanisms. System administrators should also implement monitoring solutions to detect unusual ioctl operations on storage devices and consider disabling unnecessary storage driver functionality when not required. The vulnerability's classification under ATT&CK technique T1499.004 for endpoint denial of service highlights the importance of maintaining kernel integrity and ensuring that all system components are regularly updated to address known vulnerabilities. Additionally, implementing proper privilege controls and limiting local user access to storage management interfaces can reduce the attack surface and prevent exploitation of this particular vulnerability.