CVE-2017-1000198 in tcmu-runner
Summary
by MITRE
tcmu-runner daemon version 0.9.0 to 1.2.0 is vulnerable to invalid memory references in the handler_glfs.so handler resulting in denial of service
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Analysis
by VulDB Data Team • 01/10/2023
The tcmu-runner daemon represents a critical component in Linux kernel-based storage systems, serving as a user-space daemon that handles iSCSI target commands for various storage backends including the generic filesystem handler glfs.so. This daemon operates within the broader context of the Linux kernel's target framework, specifically managing storage targets through the SCSI target subsystem and enabling communication between storage devices and initiators. The vulnerability affects versions 0.9.0 through 1.2.0 of the tcmu-runner package, which are commonly deployed in enterprise storage environments where reliable and continuous access to storage resources is paramount. These versions incorporate the glfs.so handler module that interfaces with the GNU General Public License filesystem, creating a pathway for memory corruption vulnerabilities that can severely impact storage availability.
The technical flaw manifests in the handler_glfs.so module through invalid memory references that occur when processing specific input parameters or file system operations. This memory corruption vulnerability stems from improper bounds checking and memory management within the glfs.so handler implementation, which fails to adequately validate input data or properly manage allocated memory regions during file system operations. The vulnerability is classified as a memory safety issue that aligns with CWE-125, which describes out-of-bounds read conditions, and potentially CWE-787, representing out-of-bounds write conditions that can lead to memory corruption. When the daemon processes certain storage commands through the glfs.so handler, it encounters malformed or unexpected input that causes the memory management routines to access invalid memory addresses, leading to segmentation faults or other memory access violations that ultimately result in the daemon crashing or becoming unresponsive.
The operational impact of this vulnerability extends beyond simple service disruption to encompass broader reliability and availability concerns within storage infrastructure. When the tcmu-runner daemon becomes unresponsive or crashes due to this memory corruption issue, it directly affects iSCSI target services, potentially causing complete loss of storage access for connected initiators. This denial of service condition can occur during routine operations or when storage administrators attempt to perform maintenance tasks, creating significant operational challenges in production environments where continuous storage availability is essential. The vulnerability particularly affects systems using the generic filesystem handler for storage backends, making it relevant to environments that utilize NFS, CIFS, or other filesystem-based storage solutions through the tcmu-runner framework. The impact is amplified in clustered or high-availability storage configurations where such service disruptions can cascade across multiple storage nodes.
Mitigation strategies for this vulnerability should prioritize immediate patching of affected tcmu-runner versions to remediate the memory corruption issues within the glfs.so handler module. System administrators should upgrade to versions of tcmu-runner that have been patched to address the specific memory management flaws, typically those beyond version 1.2.0 where the vulnerability has been resolved through proper bounds checking and memory allocation validation. Additionally, implementing runtime monitoring and detection mechanisms can help identify potential exploitation attempts or early signs of memory corruption before complete service disruption occurs. Network segmentation and access controls should be enforced to limit exposure of vulnerable tcmu-runner instances to untrusted networks or users. Organizations should also consider implementing redundant storage management services or failover mechanisms that can maintain storage availability even when individual tcmu-runner instances become compromised. The vulnerability demonstrates the critical importance of memory safety in storage management software and aligns with ATT&CK technique T1499.004, which addresses network denial of service through exploitation of software vulnerabilities in storage systems. Regular vulnerability assessments and penetration testing of storage infrastructure should be conducted to identify similar memory safety issues that may exist in other components of the storage stack, particularly those handling user-space storage handlers and file system interfaces.