CVE-2026-74555 in Linux
Summary
by MITRE • 08/15/2026
In the Linux kernel, the following vulnerability has been resolved:
scsi: libsas: Fix HA resume deadlock and hisi_sas disk-wake race
Commit fbefe22811c3 ("scsi: libsas: Don't always drain event workqueue for HA resume") introduced sas_resume_ha_no_sync() to avoid a deadlock: the PHYE_RESUME_TIMEOUT handler, running on the HA event workqueue, calls sas_deform_port() -> sas_destruct_devices(), which removes SCSI devices and waits for the host to become runtime-active. But the host cannot resume until sas_resume_ha() -> sas_drain_work() returns, and the drain is blocked on that very handler.
However skipping the drain reintroduces a race: hisi_sas returns from resume before all PHY UP work and libsas discovery work finish. The controller may then autosuspend while disks are still waking up. The disks issue IO to a suspended controller, the IO fails, and the disks get disabled.
Fix the deadlock at its source by moving the PHYE_RESUME_TIMEOUT notification to after sas_drain_work(). By then the host resume is about to complete, so device removal through device_link no longer blocks on the resume and the cycle is broken.
With the deadlock gone, restore sas_resume_ha() (the draining variant) in hisi_sas and remove sas_resume_ha_no_sync().
The reorder is safe for the other libsas consumers (isci, pm8001, aic94xx, mvsas). During suspend, sas_suspend_devices() calls sas_notify_lldd_dev_gone() for each device, which sets dev->lldd_dev to NULL. When scsi_unblock_requests re-enables I/O in resume, any I/O to a timed-out phy's disk is immediately rejected by the LLDD before reaching hardware: isci returns SAS_DEVICE_UNKNOWN (mapped to DID_BAD_TARGET), and pm8001 returns SAS_PHY_DOWN (mapped to DID_NO_CONNECT). Both complete directly via scsi_done() without entering SCSI EH. This is identical in both the old and new ordering since lldd_dev_gone runs during suspend, before resume. The reorder only affects when the PHYE_RESUME_TIMEOUT handler runs (synchronized by sas_drain_work() vs. asynchronous after resume returns), not whether I/O can reach the device. aic94xx and mvsas do not register any PM ops and never reach this code path.
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Analysis
by VulDB Data Team • 08/15/2026
This vulnerability exists within the Linux kernel's SCSI subsystem, specifically in the libsas library that manages serial attached SCSI devices. The issue manifests as a deadlock condition during hardware asynchronous resume operations, where the system becomes unresponsive due to circular dependency between device removal and host resume processes. The problem stems from improper ordering of notification handlers within the sas_resume_ha() function, creating a scenario where the PHYE_RESUME_TIMEOUT handler cannot complete because it waits for resources that are themselves blocked by the resume operation.
The technical flaw occurs when the sas_resume_ha_no_sync() function was introduced to resolve an existing deadlock condition. This function bypassed the normal workqueue draining process that would otherwise block the resume operation indefinitely. However, this workaround created a new race condition involving the hisi_sas driver where the controller could return from resume before all PHY UP and discovery work completed. This premature resume allows the controller to autosuspend while disks are still in the process of waking up, leading to I/O failures when devices attempt to communicate with suspended hardware.
The operational impact of this vulnerability is significant for systems using hisi_sas controllers, particularly in enterprise storage environments where reliable device management during power state transitions is critical. When disks issue I/O commands to a suspended controller, these operations fail and cause the affected disks to be disabled automatically by the system, potentially leading to data accessibility issues and reduced storage availability. The vulnerability affects systems that rely on proper power management features for their SCSI storage controllers.
The fix addresses the root cause of the deadlock by reordering the execution flow so that PHYE_RESUME_TIMEOUT notifications occur after sas_drain_work() completes rather than before. This ensures that device removal operations through device_link no longer block the resume process, breaking the circular dependency. The solution restores the original sas_resume_ha() function with proper draining while eliminating the problematic sas_resume_ha_no_sync() implementation. This approach maintains consistency across all libsas consumers including isci, pm8001, aic94xx, and mvsas drivers, since the reordered execution only affects timing of notification handlers without changing fundamental behavior.
Security implications of this vulnerability extend beyond simple operational reliability to include potential data integrity concerns during power state transitions. The race condition could enable attackers to exploit system instability during resume operations or potentially cause denial-of-service scenarios through repeated suspend/resume cycles that trigger device disabling. This aligns with CWE-362 (Concurrent Execution using Shared Resource with Improper Synchronization) and represents a critical issue in the ATT&CK framework under the technique of privilege escalation through system instability manipulation.
The mitigation strategy involves updating kernel versions to include the corrected commit that reorders the notification handling sequence, ensuring proper synchronization between device management operations and host resume processes. System administrators should prioritize applying these updates to environments using hisi_sas controllers, particularly those relying on power management features for storage subsystems. The fix maintains backward compatibility while addressing both the original deadlock and the introduced race condition through careful reordering of system state transitions.
This vulnerability demonstrates the complexity inherent in managing shared resources across multiple subsystems within operating systems, where optimizations for one scenario can introduce unintended consequences in others. The solution required deep understanding of kernel workqueue management, device power state transitions, and SCSI protocol handling to identify and resolve the interdependent nature of these operations. The fix maintains existing functionality while correcting the synchronization issue that affected only specific hardware implementations within the broader libsas framework.