On Wed, 10 Feb 2021 16:24:29 +0100 Halil Pasic pasic@linux.ibm.com wrote:
Maybe you could
- grab a reference to kvm while holding the lock
- call the mask handling functions with that kvm reference
- lock again, drop the reference, and do the rest of the processing?
I agree, matrix_mdev->kvm can go NULL any time and we are risking a null pointer dereference here.
Another idea would be to do
static void vfio_ap_mdev_unset_kvm(struct ap_matrix_mdev *matrix_mdev) { struct kvm *kvm; mutex_lock(&matrix_dev->lock); if (matrix_mdev->kvm) { kvm = matrix_mdev->kvm; matrix_mdev->kvm = NULL; mutex_unlock(&matrix_dev->lock); kvm_arch_crypto_clear_masks(kvm); mutex_lock(&matrix_dev->lock); matrix_mdev->kvm->arch.crypto.pqap_hook = NULL;
s/matrix_mdev->kvm/kvm
vfio_ap_mdev_reset_queues(matrix_mdev->mdev); kvm_put_kvm(kvm); } mutex_unlock(&matrix_dev->lock);}
That way only one unset would actually do the unset and cleanup and every other invocation would bail out with only checking matrix_mdev->kvm.
But the problem with that is that we enable the the assign/unassign prematurely, which could interfere wit reset_queues(). Forget about it.