virtio-pci: fix use after free

Commit 31a3ddda166cda86d2b5111e09ba4bda5239fae6 introduced
a use after free in virtio-pci. The main issue is
that the release method signals removal of the virtio device,
while remove signals removal of the pci device.

For example, on driver removal or hot-unplug,
virtio_pci_release_dev is called before virtio_pci_remove.
We then might get a crash as virtio_pci_remove tries to use the
device freed by virtio_pci_release_dev.

We allocate/free all resources together with the
pci device, so we can leave the release method empty.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Amit Shah <amit.shah@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Cc: stable@kernel.org

1 files changed, 6 insertions, 5 deletions

diff --git a/drivers/virtio/virtio_pci.c b/drivers/virtio/virtio_pci.c
index 79a31e5b4b6..3d1bf41e889 100644
--- a/drivers/virtio/virtio_pci.c
+++ b/drivers/virtio/virtio_pci.c
@@ -594,11 +594,11 @@ static struct virtio_config_ops virtio_pci_config_ops = {
 
 static void virtio_pci_release_dev(struct device *_d)
 {
-        struct virtio_device *dev = container_of(_d, struct virtio_device,
-                                                 dev);
-        struct virtio_pci_device *vp_dev = to_vp_device(dev);
-
-        kfree(vp_dev);
+        /*
+         * No need for a release method as we allocate/free
+         * all devices together with the pci devices.
+         * Provide an empty one to avoid getting a warning from core.
+         */
 }
 
 /* the PCI probing function */
@@ -686,6 +686,7 @@ static void __devexit virtio_pci_remove(struct pci_dev *pci_dev)
         pci_iounmap(pci_dev, vp_dev->ioaddr);
         pci_release_regions(pci_dev);
         pci_disable_device(pci_dev);
+        kfree(vp_dev);
 }
 
 #ifdef CONFIG_PM