CVE-2026-89957

Status: UPDATED  |  Advisory ID: CVE-2026-89957

Key Details

Affected Products, Subsystems & Sectors

What to Know

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

s390/vfio-ap: Fix hot-unplug skipped when last AP adapter or domain removed

The vfio_ap_mdev_hot_unplug_cfg() function uses the return value of

bitmap_andnot() to determine whether the guest APCB needs to be updated.

However, bitmap_andnot() returns false when the resulting destination

bitmap is empty. This means that if the only adapter, domain or control

domain assigned to an mdev is removed from the host's AP configuration,

the bit is correctly cleared from the shadow APCB, but bitmap_andnot()

returns false because the result is an empty bitmap. Consequently,

do_hotplug remains 0 and vfio_ap_mdev_update_guest_apcb() is never called,

leaving the KVM guest with stale hardware access to the unplugged AP

devices.

Fix this by replacing the bitmap_andnot() return value check with

bitmap_intersects() to determine whether the shadow APCB actually

overlaps with the removal mask. If there is an intersection, call

bitmap_andnot() solely for its side effect of clearing the bits, then

unconditionally set do_hotplug to trigger the guest APCB update. (NVD)

What to Do

Monitor Linux's web page for any future patch releases.

References