Linux Kernel Migration Vulnerability in KVM Hosting Environments

CVE-2026-89756

What is CVE-2026-89756?

A recently discovered issue in the Linux kernel affects the migration process in KVM hosting environments. Specifically, the function migrate_pages_batch() fails to report quiescent states for tasks during prolonged unmapping processes. This oversight can lead to RCU stalls, particularly involving the kcompactd task, resulting in significant delays in the Tasks-RCU grace period. The underlying problem stems from the inefficacy of cond_resched() in preemption kernels, causing long-running batches to hinder system performance and overall efficiency. This vulnerability underscores the importance of effective resource management and the need for timely resolution to ensure optimal operations in environments heavily reliant on virtualized systems.

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