[4.2.y-ckt stable] Patch "virtio_pci: fix use after free on release" has been added to the 4.2.y-ckt tree

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    virtio_pci: fix use after free on release

to the linux-4.2.y-queue branch of the 4.2.y-ckt extended stable tree 
which can be found at:

    http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-4.2.y-queue

This patch is scheduled to be released in version 4.2.8-ckt4.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 4.2.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

---8<------------------------------------------------------------

>From 257dc21a265e11ee5db3bba8b52793808eb30abf Mon Sep 17 00:00:00 2001
From: "Michael S. Tsirkin" <mst at redhat.com>
Date: Thu, 14 Jan 2016 16:00:41 +0200
Subject: virtio_pci: fix use after free on release

commit 2989be09a8a9d62a785137586ad941f916e08f83 upstream.

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 <jmarchan at redhat.com>
Cc: Sasha Levin <sasha.levin at oracle.com>
Signed-off-by: Michael S. Tsirkin <mst at redhat.com>
Tested-by: Jerome Marchand <jmarchan at redhat.com>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 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 78f804a..2046a68 100644
--- a/drivers/virtio/virtio_pci_common.c
+++ b/drivers/virtio/virtio_pci_common.c
@@ -545,6 +545,7 @@ 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);

@@ -554,6 +555,7 @@ static void virtio_pci_remove(struct pci_dev *pci_dev)
 		virtio_pci_modern_remove(vp_dev);

 	pci_disable_device(pci_dev);
+	put_device(dev);
 }

 static struct pci_driver virtio_pci_driver = {
--
1.9.1