KVM: arm64: vgic: Check the interrupt is still ours before migrating it

KVM: arm64: vgic: Check the interrupt is still ours before migrating it

vgic_prune_ap_list() drops both ap_list_lock and irq_lock while migrating
an interrupt to another vCPU. After reacquiring the locks it only checks
that the affinity is unchanged (target_vcpu == vgic_target_oracle(irq))
before moving the interrupt, which assumes that an interrupt whose affinity
is preserved is still queued on this vCPU's ap_list.

That assumption no longer holds if the interrupt is taken off the ap_list
while the locks are dropped. vgic_flush_pending_lpis() removes the
interrupt from the list and sets irq->vcpu to NULL, but leaves
enabled/pending/target_vcpu untouched. As the interrupt is still enabled
and pending, vgic_target_oracle() returns the same target_vcpu, so the
affinity check passes and list_del() is run a second time on an entry that
has already been removed.

Also check that the interrupt is still assigned to this vCPU
(irq->vcpu == vcpu) before moving it.

Fixes: 0919e84c0fc1 ("KVM: arm/arm64: vgic-new: Add IRQ sync/flush framework")
Signed-off-by: Hyunwoo Kim <imv4bel@gmail.com>
Link: https://patch.msgid.link/aiHnI1mu6SGQrgnz@v4bel
Signed-off-by: Marc Zyngier <maz@kernel.org>
Cc: stable@vger.kernel.org