CVE-2020-12652 in Linux
Summary
by MITRE
The __mptctl_ioctl function in drivers/message/fusion/mptctl.c in the Linux kernel before 5.4.14 allows local users to hold an incorrect lock during the ioctl operation and trigger a race condition, i.e., a "double fetch" vulnerability, aka CID-28d76df18f0a. NOTE: the vendor states "The security impact of this bug is not as bad as it could have been because these operations are all privileged and root already has enormous destructive power."
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Analysis
by VulDB Data Team • 10/15/2020
The vulnerability described in CVE-2020-12652 resides within the Linux kernel's message fusion subsystem, specifically in the __mptctl_ioctl function located at drivers/message/fusion/mptctl.c. This flaw represents a critical race condition that manifests as a double fetch vulnerability, where the kernel fails to properly maintain lock consistency during ioctl operations. The issue affects Linux kernel versions prior to 5.4.14, creating a persistent security risk for systems running vulnerable kernel versions. The vulnerability operates through a complex interaction between lock management and ioctl processing that ultimately allows for improper resource handling and potential privilege escalation scenarios.
The technical implementation of this vulnerability stems from improper lock management during the ioctl operation execution. When the __mptctl_ioctl function processes certain commands, it fails to maintain consistent lock state throughout the operation lifecycle, creating a window where the same data can be accessed and modified by multiple code paths simultaneously. This double fetch condition occurs when the kernel retrieves data, releases locks, and then re-fetches the same data without proper validation, allowing for inconsistent state handling. The vulnerability specifically impacts the mptctl driver which interfaces with message processing units, commonly found in storage controllers and enterprise networking equipment. This flaw aligns with CWE-362, which describes race conditions in concurrent programming, and represents a classic example of improper lock handling that violates fundamental concurrency control principles.
The operational impact of this vulnerability extends beyond simple privilege escalation to encompass potential system instability and data integrity concerns. While the vendor acknowledges that the security impact is somewhat mitigated because these operations require privileged access, the vulnerability remains concerning due to the potential for privilege escalation and system compromise. An attacker with local access could exploit this race condition to manipulate kernel memory structures, potentially leading to denial of service, information disclosure, or even full system compromise. The vulnerability's presence in the message fusion subsystem means that systems utilizing storage controllers, network adapters, or other hardware components that rely on this driver could be at risk. This aligns with ATT&CK technique T1068, which covers local privilege escalation through kernel vulnerabilities, and demonstrates how seemingly minor lock management flaws can create significant security risks in kernel space operations.
Mitigation strategies for CVE-2020-12652 primarily focus on kernel version updates and access control measures. The most effective solution involves upgrading to Linux kernel version 5.4.14 or later, where the race condition has been properly addressed through corrected lock management. System administrators should prioritize patching affected systems, particularly those running enterprise storage or networking equipment that relies on the mptctl driver. Additionally, implementing strict access controls and limiting local user privileges can reduce the attack surface, though this does not eliminate the underlying vulnerability. The fix typically involves ensuring proper lock acquisition and release patterns throughout the ioctl operation, preventing the double fetch scenario that enables the race condition. Organizations should also monitor for similar vulnerabilities in other kernel subsystems and maintain comprehensive patch management processes to address future exploits targeting kernel concurrency mechanisms.