CVE-2012-4542 in Linux
Summary
by MITRE
block/scsi_ioctl.c in the Linux kernel through 3.8 does not properly consider the SCSI device class during authorization of SCSI commands, which allows local users to bypass intended access restrictions via an SG_IO ioctl call that leverages overlapping opcodes.
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Analysis
by VulDB Data Team • 12/29/2021
The vulnerability described in CVE-2012-4542 represents a critical authorization flaw within the Linux kernel's SCSI subsystem that affects versions through 3.8. This issue resides in the block/scsi_ioctl.c file where the kernel fails to properly validate SCSI device classes during the authorization process for SCSI commands. The flaw specifically manifests when local users exploit the SG_IO ioctl call to manipulate overlapping opcodes, effectively bypassing intended access controls that should restrict unauthorized operations on SCSI devices. This vulnerability demonstrates a fundamental breakdown in the kernel's privilege enforcement mechanisms, particularly concerning device access control and command authorization.
The technical implementation of this vulnerability stems from insufficient validation of device class parameters within the SCSI command authorization framework. When a user issues an SG_IO ioctl request, the kernel should verify that the requesting process has appropriate permissions based on the target device's class and the specific SCSI command being executed. However, the kernel's authorization logic fails to properly consider the SCSI device class during this validation process, creating a pathway for privilege escalation. The overlapping opcodes aspect indicates that the vulnerability exploits the way certain SCSI commands are interpreted when their opcode values overlap with those of other commands, allowing maliciously crafted requests to bypass security checks that would normally prevent access to restricted device operations.
The operational impact of this vulnerability is significant for systems running affected Linux kernel versions, as it provides local users with the ability to bypass access restrictions that should protect sensitive SCSI devices. Attackers could potentially access or manipulate storage devices that they should not have authorization to control, leading to data exposure, system integrity compromise, or denial of service conditions. The vulnerability is particularly concerning because it operates at the kernel level and can be exploited by any local user, making it a persistent threat to system security. Systems that rely heavily on SCSI storage configurations, including enterprise servers and storage arrays, would be especially vulnerable to this type of unauthorized access.
Mitigation strategies for CVE-2012-4542 focus primarily on kernel updates and system hardening measures. The most effective solution involves upgrading to a Linux kernel version that contains the fix for this vulnerability, which was implemented in kernel versions beyond 3.8. System administrators should also implement proper access controls and monitoring to detect unauthorized SCSI command executions. The vulnerability aligns with CWE-284, which describes improper access control in software systems, and represents a specific instance of privilege escalation through inadequate authorization checks. From an ATT&CK framework perspective, this vulnerability maps to privilege escalation techniques and can be categorized under T1068, which involves exploiting local system privileges to gain elevated access. Additional defensive measures include implementing mandatory access controls, monitoring ioctl system calls, and ensuring that only authorized processes have access to SCSI device interfaces through proper user and group permissions.