CVE-2026-93238

/// Technical description

In the Linux kernel, the following vulnerability has been resolved:

s390/vfio-ap: fix potential use of uninitialized apm_filtered bitmap

The DECLARE_BITMAP(apm_filtered, AP_DEVICES) macro allocates the bitmap

on the stack without zero-initializing it.

In vfio_ap_mdev_hot_plug_cfg(), the vfio_ap_mdev_filter_matrix() function

is only called to initialize and populate apm_filtered if either

filter_adapters or filter_domains is true. If the hot plug configuration

change only adds control domains (meaning filter_cdoms is true, but

filter_adapters and filter_domains are both false),

vfio_ap_mdev_filter_matrix() is bypassed.

Consequently, apm_filtered is passed to reset_queues_for_apids() with

uninitialized stack garbage. This can cause reset_queues_for_apids() to

interpret arbitrary stack garbage bits as valid APIDs to reset, potentially

performing unintended guest hardware queue resets.

Fix this by zero-initializing the apm_filtered bitmap at the beginning of

vfio_ap_mdev_hot_plug_cfg(

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References