KVM: only allow one gsi per fd
Looks like repeatedly binding same fd to multiple gsi's with irqfd can
use up a ton of kernel memory for irqfd structures.
A simple fix is to allow each fd to only trigger one gsi: triggering a
storm of interrupts in guest is likely useless anyway, and we can do it
by binding a single gsi to many interrupts if we really want to.
Cc: stable@kernel.org
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Acked-by: Gregory Haskins <ghaskins@novell.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
diff --git a/virt/kvm/eventfd.c b/virt/kvm/eventfd.c
index 30f70fd..62e4cd9 100644
--- a/virt/kvm/eventfd.c
+++ b/virt/kvm/eventfd.c
@@ -166,7 +166,7 @@
static int
kvm_irqfd_assign(struct kvm *kvm, int fd, int gsi)
{
- struct _irqfd *irqfd;
+ struct _irqfd *irqfd, *tmp;
struct file *file = NULL;
struct eventfd_ctx *eventfd = NULL;
int ret;
@@ -203,9 +203,20 @@
init_waitqueue_func_entry(&irqfd->wait, irqfd_wakeup);
init_poll_funcptr(&irqfd->pt, irqfd_ptable_queue_proc);
+ spin_lock_irq(&kvm->irqfds.lock);
+
+ ret = 0;
+ list_for_each_entry(tmp, &kvm->irqfds.items, list) {
+ if (irqfd->eventfd != tmp->eventfd)
+ continue;
+ /* This fd is used for another irq already. */
+ ret = -EBUSY;
+ spin_unlock_irq(&kvm->irqfds.lock);
+ goto fail;
+ }
+
events = file->f_op->poll(file, &irqfd->pt);
- spin_lock_irq(&kvm->irqfds.lock);
list_add_tail(&irqfd->list, &kvm->irqfds.items);
spin_unlock_irq(&kvm->irqfds.lock);