[added to the 4.1 stable tree] virtio_pci: fix use after free on release

From: "Michael S. Tsirkin" <mst@redhat.com>

This patch has been added to the 4.1 stable tree. If you have any
objections, please let us know.

===============

[ Upstream commit 2989be09a8a9d62a785137586ad941f916e08f83 ]

KASan detected a use-after-free error in virtio-pci remove code. In
virtio_pci_remove(), vp_dev is still used after being freed in
unregister_virtio_device() (in virtio_pci_release_dev() more
precisely).

To fix, keep a reference until cleanup is done.

Fixes: 63bd62a08ca4 ("virtio_pci: defer kfree until release callback")
Reported-by: Jerome Marchand <redacted>
Cc: stable@vger.kernel.org
Cc: Sasha Levin <redacted>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Tested-by: Jerome Marchand <redacted>
Signed-off-by: Sasha Levin <redacted>
---
 drivers/virtio/virtio_pci_common.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/virtio/virtio_pci_common.c b/drivers/virtio/virtio_pci_common.c
index eba1b7a..14f767e 100644
--- a/drivers/virtio/virtio_pci_common.c
+++ b/drivers/virtio/virtio_pci_common.c

@@ -554,6 +554,7 @@ err_enable_device:
 static void virtio_pci_remove(struct pci_dev *pci_dev)
 {
 	struct virtio_pci_device *vp_dev = pci_get_drvdata(pci_dev);
+	struct device *dev = get_device(&vp_dev->vdev.dev);
 
 	unregister_virtio_device(&vp_dev->vdev);
 

@@ -564,6 +565,7 @@ static void virtio_pci_remove(struct pci_dev *pci_dev)
 
 	pci_release_regions(pci_dev);
 	pci_disable_device(pci_dev);
+	put_device(dev);
 }
 
 static struct pci_driver virtio_pci_driver = {

-- 
2.5.0