CVE-2013-2140 in Linux
Summary
by MITRE
The dispatch_discard_io function in drivers/block/xen-blkback/blkback.c in the Xen blkback implementation in the Linux kernel before 3.10.5 allows guest OS users to cause a denial of service (data loss) via filesystem write operations on a read-only disk that supports the (1) BLKIF_OP_DISCARD (aka discard or TRIM) or (2) SCSI UNMAP feature.
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Analysis
by VulDB Data Team • 05/14/2021
The vulnerability identified as CVE-2013-2140 resides within the Xen blkback implementation in the Linux kernel, specifically in the dispatch_discard_io function located in drivers/block/xen-blkback/blkback.c. This flaw represents a critical security issue that affects systems running Linux kernel versions prior to 3.10.5, creating a potential pathway for malicious actors to exploit read-only disk configurations and cause unintended data loss or system disruption. The vulnerability operates through the manipulation of filesystem write operations on read-only disks that support either BLKIF_OP_DISCARD functionality or SCSI UNMAP capabilities, which are standard features designed for efficient storage management.
The technical flaw stems from an improper handling of discard operations within the block backend driver when dealing with read-only virtual disks. When a guest operating system attempts to perform discard operations on a read-only disk, the dispatch_discard_io function fails to properly validate the disk's read-only status before processing the discard request. This validation gap allows malicious or compromised guest OS users to issue discard commands that should be rejected due to the disk's read-only nature. The function processes these invalid requests without proper authorization checks, leading to potential data corruption or loss scenarios where the system may inadvertently modify or clear data that should remain protected.
The operational impact of this vulnerability extends beyond simple denial of service to encompass potential data integrity compromise. Attackers exploiting this vulnerability can manipulate the virtual storage environment to cause unexpected behavior during filesystem operations, particularly when the guest OS attempts to perform TRIM or UNMAP operations on read-only virtual disks. This creates a scenario where legitimate system operations may be disrupted, potentially leading to complete system instability or data loss in environments where virtualized storage is heavily utilized. The vulnerability particularly affects virtualized environments using Xen hypervisor where multiple guest operating systems share underlying storage resources, making it a significant concern for cloud computing and virtualization platforms.
The exploitability of this vulnerability aligns with attack patterns documented in the MITRE ATT&CK framework under the category of privilege escalation and resource exhaustion techniques, where attackers leverage improper access controls to manipulate system resources. This vulnerability maps to CWE-284, which describes improper access control, and CWE-362, which addresses concurrent execution using shared resources. The security implications are particularly severe in multi-tenant cloud environments where guest OS users may attempt to exploit such flaws to disrupt other virtual machines or compromise the integrity of shared storage resources. Organizations utilizing virtualized infrastructure should consider implementing additional monitoring and access control measures to detect and prevent unauthorized discard operations on read-only virtual disks.
Mitigation strategies for CVE-2013-2140 primarily focus on upgrading the Linux kernel to version 3.10.5 or later, which includes the necessary patches to properly validate discard operations against read-only disk states. System administrators should also implement proper virtualization security controls, including monitoring for unusual discard operations and restricting guest OS capabilities when operating with read-only disk configurations. Additional defensive measures include implementing hypervisor-level access controls and regularly auditing virtual machine storage configurations to ensure that read-only disks are properly enforced. Organizations should also consider implementing network segmentation and access controls to limit the potential impact of such vulnerabilities in their virtualized environments, particularly in scenarios where guest OS users may have elevated privileges or access to storage management functions.