Linux Kernel PREEMPT_RT Scheduling Issue in storvsc SCSI Driver

A scheduling while atomic vulnerability has been identified in the Linux kernel's SCSI storvsc driver, specifically in versions prior to the latest commit. This issue occurs when the kernel is running with PREEMPT_RT enabled on Hyper-V, leading to a lock-up situation. The problem arises because the storvsc driver, which handles SCSI commands in a virtualized environment, improperly manages CPU preemption, causing the system to become unresponsive under certain workloads.

Impact

The vulnerability can cause a system lock-up, where the kernel fails to properly schedule tasks, leading to a denial of service condition.

Reproduction

The vulnerability can be reproduced by running a workload that stresses the I/O subsystem, such as with the 'stress-ng' tool, while the system is configured with the PREEMPT_RT kernel option enabled. This combination can trigger the scheduling while atomic bug, causing the system to lock up.

Remediation

Users can upgrade to the latest version of the Linux kernel stable release, where this issue has been addressed.