CVE-2021-47045 in Linux
Summary
by MITRE • 02/28/2024
In the Linux kernel, the following vulnerability has been resolved:
scsi: lpfc: Fix null pointer dereference in lpfc_prep_els_iocb()
It is possible to call lpfc_issue_els_plogi() passing a did for which no matching ndlp is found. A call is then made to lpfc_prep_els_iocb() with a null pointer to a lpfc_nodelist structure resulting in a null pointer dereference.
Fix by returning an error status if no valid ndlp is found. Fix up comments regarding ndlp reference counting.
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Analysis
by VulDB Data Team • 12/06/2024
The vulnerability identified as CVE-2021-47045 resides within the Linux kernel's SCSI subsystem, specifically affecting the LightPulse Fibre Channel (lpfc) driver implementation. This issue represents a critical null pointer dereference flaw that can potentially lead to system instability and denial of service conditions. The lpfc driver is responsible for managing Fibre Channel host bus adapters and facilitating communication between storage devices and the operating system through SCSI protocols. The vulnerability manifests during the processing of ELS (Extended Link Services) commands, particularly when handling logon operations within the Fibre Channel fabric environment.
The technical flaw occurs in the lpfc_prep_els_iocb() function where the driver fails to properly validate the existence of a node list pointer before attempting to dereference it. When lpfc_issue_els_plogi() is invoked with a destination identifier (did) that does not correspond to any existing node list pointer (ndlp), the function proceeds to call lpfc_prep_els_iocb() with a null pointer parameter. This scenario violates fundamental defensive programming principles and creates an execution path where the kernel attempts to access memory at a null address location, resulting in immediate system termination or panic conditions. The vulnerability is categorized under CWE-476 as a null pointer dereference, which represents one of the most common and dangerous types of memory corruption errors in kernel space code.
The operational impact of this vulnerability extends beyond simple system crashes, as it can be exploited to cause denial of service attacks against storage infrastructure. In enterprise environments where Fibre Channel storage networks are critical for data availability, this flaw could enable malicious actors or accidental system states to disrupt storage communications and potentially compromise entire storage fabrics. The vulnerability affects systems running Linux kernels with the lpfc driver and is particularly concerning because it occurs during normal operation when the driver processes incoming ELS commands, making it difficult to predict or prevent through standard operational procedures. According to ATT&CK framework category T1499, this vulnerability could enable adversaries to disrupt services and impact system availability.
The fix implemented for CVE-2021-47045 addresses the root cause by introducing proper validation logic that returns an error status when no valid node list pointer is found, preventing the null pointer dereference from occurring. This solution aligns with secure coding practices that emphasize defensive programming and proper error handling in kernel space operations. Additionally, the patch includes corrections to comments regarding node list pointer reference counting, which helps maintain code clarity and prevents similar issues from arising in future modifications. The resolution demonstrates proper resource management and validation techniques that should be applied throughout kernel subsystems to prevent similar null pointer dereference vulnerabilities. The fix ensures that the lpfc driver properly handles edge cases and invalid input conditions, thereby improving the overall robustness and security posture of the Linux kernel's storage subsystem.