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virtio_pci: defer kfree until release callback

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A struct device which has just been unregistered can live on past the
point at which a driver decides to drop it's initial reference to the
kobject gained on allocation.

This implies that when releasing a virtio device, we can't free a struct
virtio_device until the underlying struct device has been released,
which might not happen immediately on device_unregister().

Unfortunately, this is exactly what virtio pci does:
it has an empty release callback, and frees memory immediately
after unregistering the device.

This causes an easy to reproduce crash if CONFIG_DEBUG_KOBJECT_RELEASE
it enabled.

To fix, free the memory only once we know the device is gone in the release
callback.

Cc: stable@vger.kernel.org
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
This commit is contained in:
Sasha Levin 2015-01-02 14:47:40 -05:00 committed by Michael S. Tsirkin
parent 945399a8c7
commit 63bd62a08c
1 changed files with 4 additions and 6 deletions
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10
drivers/virtio/virtio_pci_legacy.c
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@ -213,11 +213,10 @@ static const struct virtio_config_ops virtio_pci_config_ops = {
static void virtio_pci_release_dev(struct device *_d) static void virtio_pci_release_dev(struct device *_d)
{ {
/* struct virtio_device *vdev = dev_to_virtio(_d);
* No need for a release method as we allocate/free struct virtio_pci_device *vp_dev = to_vp_device(vdev);
* all devices together with the pci devices.
* Provide an empty one to avoid getting a warning from core. kfree(vp_dev);
*/
} }
/* the PCI probing function */ /* the PCI probing function */
@ -311,5 +310,4 @@ void virtio_pci_legacy_remove(struct pci_dev *pci_dev)
pci_iounmap(pci_dev, vp_dev->ioaddr); pci_iounmap(pci_dev, vp_dev->ioaddr);
pci_release_regions(pci_dev); pci_release_regions(pci_dev);
pci_disable_device(pci_dev); pci_disable_device(pci_dev);
kfree(vp_dev);
} }