In the Linux kernel, the following vulnerability has been resolved: s390/vfio-ap: fix potential use of uninitialized apm_filtered bitmap T

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() using bitmap_zero().