[PATCH v1 1/6] kvm: s390: Reject setting flic pfault attributes on ucontrol VMs

Christoph Schlameuss
2024-12-09T15:24:07Z

Prevent null pointer dereference when processing the
KVM_DEV_FLIC_APF_ENABLE and KVM_DEV_FLIC_APF_DISABLE_WAIT ioctls in the
interrupt controller.

Fixes: 3c038e6be0e2 ("KVM: async_pf: Async page fault support on s390")
Reported-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Signed-off-by: Christoph Schlameuss <schlameuss@linux.ibm.com>
---

Added documentation and fixes comment.

---
Documentation/virt/kvm/devices/s390_flic.rst | 4 ++++
arch/s390/kvm/interrupt.c | 4 ++++
2 files changed, 8 insertions(+)

diff --git a/Documentation/virt/kvm/devices/s390_flic.rst b/Documentation/virt/kvm/devices/s390_flic.rst
index ea96559ba501..b784f8016748 100644
--- a/Documentation/virt/kvm/devices/s390_flic.rst
+++ b/Documentation/virt/kvm/devices/s390_flic.rst
@@ -58,11 +58,15 @@ Groups:
Enables async page faults for the guest. So in case of a major page fault
the host is allowed to handle this async and continues the guest.

+ -EINVAL is returned when called on the FLIC of a ucontrol VM.
+
KVM_DEV_FLIC_APF_DISABLE_WAIT
Disables async page faults for the guest and waits until already pending
async page faults are done. This is necessary to trigger a completion interrupt
for every init interrupt before migrating the interrupt list.

+ -EINVAL is returned when called on the FLIC of a ucontrol VM.
+
KVM_DEV_FLIC_ADAPTER_REGISTER
Register an I/O adapter interrupt source. Takes a kvm_s390_io_adapter
describing the adapter to register::
diff --git a/arch/s390/kvm/interrupt.c b/arch/s390/kvm/interrupt.c
index ea8dce299954..22d73c13e555 100644
--- a/arch/s390/kvm/interrupt.c
+++ b/arch/s390/kvm/interrupt.c
@@ -2678,9 +2678,13 @@ static int flic_set_attr(struct kvm_device *dev, struct kvm_device_attr *attr)
kvm_s390_clear_float_irqs(dev->kvm);
break;
case KVM_DEV_FLIC_APF_ENABLE:
+ if (kvm_is_ucontrol(dev->kvm))
+ return -EINVAL;
dev->kvm->arch.gmap->pfault_enabled = 1;
break;
case KVM_DEV_FLIC_APF_DISABLE_WAIT:
+ if (kvm_is_ucontrol(dev->kvm))
+ return -EINVAL;
dev->kvm->arch.gmap->pfault_enabled = 0;
/*
* Make sure no async faults are in transition when
--
2.47.1