Re: [PATCH v3 9/9] s390/vfio-ap: Fix memory leak when queue removed from host AP config

[Matthew Rosato <mjrosato@linux.ibm.com>]

On 8/12/26 7:51 AM, Anthony Krowiak wrote:
> When an adapter or domain is removed from the host's AP configuration, the
> AP bus invokes vfio_ap_on_cfg_changed() to notify the vfio_ap device
> driver. For each ap_matrix_mdev object to which the adapter or domain
> is assigned, vfio_ap_mdev_hot_unplug_cfg() is called and removes the
> adapter or domain from the matrix_mdev->shadow_apcb (i.e., the guest's AP
> configuration) and hot unplugs it if a guest is using it. The new host
> AP configuration (sans adapter or domain) is then stored in
> matrix_dev->info.
> 
> When the AP bus subsequently unbinds the physical queue devices associated
> with the adapter or domain that has been removed, it invokes
> vfio_ap_mdev_remove_queue() for each queue removed. At this point, the
> adapter or domain will no longer be assigned to the
> matrix_mdev->shadow_apcb or the matrix_dev->info object because they would
> have been removed by vfio_ap_on_cfg_changed(). Consequently,
> vfio_ap_mdev_reset_queue(q) is bypassed and kfree(q) is called
> without executing vfio_ap_free_aqic_resources(). This indefinitely pins
> guest memory (q->saved_iova) and leaks KVM GISC resources (q->saved_isc).
> 
> Note that resetting the queue would fail with an invalid APQN error due to
> the fact the queue is not longer in the host's AP configuration; however,
> it is still necessary to free the AQIC resources. The fix here is to call
> vfio_ap_free_aqic_resources if the adapter or domain is neither in
> matrix_mdev->shadow_apcb or matrix_dev->info.
> 
> Fixes: b9bd10c43456d ("s390/vfio-ap: do not reset queue removed from host config")
> Cc: stable@vger.kernel.org
> Signed-off-by: Anthony Krowiak <akrowiak@linux.ibm.com>

Reviewed-by: Matthew Rosato <mjrosato@linux.ibm.com>