In the Linux kernel, the following vulnerability has been resolved: s390/vfio-ap: fix KVM GISC and page leak when queue removed from host config… (CVE-2026-98473)

This vulnerability in the Linux kernel affects the s390 vfio-ap driver, specifically in the handling of KVM interrupt and page resources when a queue is removed from the host's AP configuration while assigned to a mediated device (mdev). Three related problems were identified: (1) AP_RESPONSE_Q_NOT_AVAIL was not handled in vfio_ap_mdev_reset_queue(), causing leaks of KVM GISC registration and pinned guest pages; (2) apq_status_check() did not handle AP_RESPONSE_Q_NOT_AVAIL, potentially causing similar leaks; (3) vfio_ap_free_aqic_resources() could leak saved_isc when the kvm pointer was NULL, risking a double-free. The patch adds handling for AP_RESPONSE_Q_NOT_AVAIL in relevant functions and separates resource cleanup logic to prevent leaks and double-free conditions.

The vulnerability can lead to resource leaks in the KVM guest environment, specifically leaking KVM GISC registrations and pinned guest pages, which could degrade system stability or resource availability. Additionally, a potential double-free condition could cause kernel instability or crashes. There is no indication of direct code execution or privilege escalation from the provided information.

A fix has been implemented in the Linux kernel to properly handle the AP_RESPONSE_Q_NOT_AVAIL response code and to correct resource cleanup logic in the vfio-ap driver. Users should apply the official kernel updates that include this patch to resolve the issue. No additional mitigation steps are indicated by the vendor advisory.