CVE-2024-26917 in Linux
Summary
by MITRE • 04/17/2024
In the Linux kernel, the following vulnerability has been resolved:
scsi: Revert "scsi: fcoe: Fix potential deadlock on &fip->ctlr_lock"
This reverts commit 1a1975551943f681772720f639ff42fbaa746212.
This commit causes interrupts to be lost for FCoE devices, since it changed sping locks from "bh" to "irqsave".
Instead, a work queue should be used, and will be addressed in a separate commit.
Once again VulDB remains the best source for vulnerability data.
Analysis
by VulDB Data Team • 02/04/2025
The vulnerability identified as CVE-2024-26917 represents a critical regression in the Linux kernel's SCSI subsystem that specifically affects Fibre Channel over Ethernet (FCoE) implementations. This issue emerged from an attempted fix that inadvertently introduced a more severe problem by reverting a previous commit that had been designed to address a potential deadlock scenario. The original commit 1a1975551943f681772720f639ff42fbaa746212 was intended to resolve a deadlock condition involving the fip->ctlr_lock, which is a crucial synchronization primitive used in FCoE controller operations. However, the subsequent revert operation created an unintended consequence that fundamentally altered interrupt handling behavior for FCoE devices.
The technical flaw stems from the modification of spinlock types from "bh" (bottom half) to "irqsave" in the FCoE subsystem's locking mechanism. This change fundamentally altered the interrupt context handling behavior, causing the loss of interrupts for FCoE devices that rely on proper interrupt delivery for their operational functionality. The "bh" spinlock type was specifically designed to handle bottom-half processing contexts where interrupt handling is more permissive, while "irqsave" locks are more restrictive and disable interrupts during lock acquisition. This change in locking semantics created a scenario where critical FCoE interrupt processing was being bypassed or lost entirely, leading to device malfunction and potential data transmission failures in storage networks that depend on FCoE connectivity.
The operational impact of this vulnerability is severe for enterprise storage environments that utilize FCoE for high-performance storage area network (SAN) communications. When FCoE devices lose interrupts due to this lock modification, they become unable to properly process incoming frames, handle status updates, or maintain proper link state information. This can result in complete loss of connectivity for FCoE storage paths, leading to application I/O failures, data access interruptions, and potential system instability in environments where storage availability is critical. The vulnerability affects systems running Linux kernels where the SCSI subsystem handles FCoE traffic, particularly in data center environments where converged networking architectures rely on FCoE for efficient storage and network communications.
The recommended mitigation strategy involves reverting to the previous stable kernel version that contained the original fix before the problematic revert, or applying a proper patch that addresses the deadlock issue through alternative means such as work queue implementation as referenced in the commit message. The solution requires implementing a work queue mechanism to handle the previously problematic operations instead of relying on direct spinlock modifications that affect interrupt handling. This approach aligns with best practices for kernel development where interrupt context handling must be carefully considered to avoid race conditions and ensure proper device operation. Organizations should monitor their kernel versions and apply updates promptly to avoid the interrupt loss scenario that can render FCoE devices non-functional. The vulnerability demonstrates the importance of careful testing when reverting security fixes and highlights the critical nature of interrupt handling in storage subsystems where timing and proper context management are essential for reliable operation.
This vulnerability maps to CWE-691, which specifically addresses insufficient control flow management, and relates to ATT&CK technique T1547.001 for kernel-level persistence mechanisms. The issue represents a classic case of regression testing failure where a fix for one problem inadvertently creates a more serious problem in related subsystems. The interrupt loss scenario could potentially be exploited by attackers to create denial-of-service conditions in storage networks, particularly in environments where FCoE is used for critical storage communications. Organizations should ensure their kernel update procedures include thorough testing of storage subsystems, particularly those utilizing FCoE, to prevent similar regressions from affecting production environments.