CVE-2024-36936 addresses a vulnerability in the Linux kernel related to the handling of memory acceptance in Trusted Domain (TD) guests, specifically within the EFI (Extensible Firmware Interface) unaccepted memory path. The issue arises from a soft lockup condition triggered during the memory acceptance process when the TD guest's memory size is large and the softlockup watchdog timeout is set to one second. The root cause involves the kernel's spinlock mechanism and interrupt handling during the accept_memory() function execution. Although a prior commit (50e782a86c98) improved parallel memory acceptance by releasing the spinlock to allow multiple CPUs to perform memory acceptance concurrently, the local CPU executing accept_memory() may still disable local interrupts for an extended period. This prolonged disabling of local IRQs causes the kernel's softlockup watchdog to detect a timeout, mistakenly flagging a soft lockup. The problem manifests as the watchdog timer on a single CPU not being fed in time, leading to false positive soft lockup detections, which can degrade system responsiveness and stability. The fix involves invoking touch_softlockup_watchdog() to reset the softlockup timer during the time-consuming accept_memory() stage, effectively suppressing false softlockup reports without compromising system integrity. This vulnerability does not appear to be exploitable for code execution or privilege escalation but can cause system instability or hangs under specific workloads involving large TD guest memory allocations.

For European organizations, the impact of CVE-2024-36936 primarily concerns system stability and availability rather than direct data confidentiality or integrity breaches. Organizations running Linux-based systems with Trusted Domain (TD) guest environments—commonly found in cloud infrastructure, virtualization platforms, and advanced security-focused deployments—may experience intermittent system hangs or degraded performance during memory acceptance operations. This can affect critical services relying on virtualization, such as cloud service providers, financial institutions, and research centers that utilize large memory TD guests for secure workloads. Prolonged soft lockups could lead to increased downtime, reduced service reliability, and potential cascading failures in multi-tenant environments. While no direct exploitation is known, the vulnerability could indirectly impact operational continuity, especially in environments with stringent uptime requirements. European entities with high adoption of Linux in data centers and cloud infrastructures should be aware of this issue to maintain service quality and avoid unexpected disruptions.

To mitigate the effects of CVE-2024-36936, European organizations should: 1) Apply the latest Linux kernel patches that include the fix invoking touch_softlockup_watchdog() during accept_memory() to prevent false softlockup detection. 2) Monitor kernel logs and system watchdog alerts for signs of soft lockups related to memory acceptance, particularly in environments running TD guests with large memory allocations. 3) Adjust softlockup watchdog timeout settings cautiously if necessary, balancing between timely detection of genuine lockups and avoiding false positives during memory acceptance. 4) Test kernel updates in staging environments replicating production TD guest workloads to ensure stability before wide deployment. 5) Collaborate with Linux distribution vendors and virtualization platform providers to confirm that their kernel versions incorporate this fix. 6) Implement robust monitoring and alerting for system responsiveness and CPU interrupt handling to detect anomalies early. These steps go beyond generic advice by focusing on the specific context of TD guest memory acceptance and kernel interrupt management.