[PATCH 2/2] kvm: validate irqfd type

[Gregory Haskins <ghaskins@novell.com>]

We should be more vigilant in validating the fd type passed down for use
in irqfd.  A malicious userspace could do something nasty like pass the
kvm fd which would cause problems such as a reference leak on the kvm
object on shutdown.

Therefore, we use the eventfd_fget() routine in place of the plain fget()
to at least make sure its of the proper type.

Reported-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Gregory Haskins <ghaskins@novell.com>
---

 virt/kvm/eventfd.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/virt/kvm/eventfd.c b/virt/kvm/eventfd.c
index c63ff6a..f3f2ea1 100644
--- a/virt/kvm/eventfd.c
+++ b/virt/kvm/eventfd.c
@@ -27,6 +27,7 @@
 #include <linux/poll.h>
 #include <linux/file.h>
 #include <linux/list.h>
+#include <linux/eventfd.h>
 
 /*
  * --------------------------------------------------------------------
@@ -102,7 +103,7 @@ kvm_assign_irqfd(struct kvm *kvm, int fd, int gsi)
 	/*
 	 * Embed the file* lifetime in the irqfd.
 	 */
-	file = fget(fd);
+	file = eventfd_fget(fd);
 	if (IS_ERR(file)) {
 		ret = PTR_ERR(file);
 		goto fail;