2020-06-16 21:31:22

by Alex Williamson

Subject: [PATCH] vfio/pci: Clear error and request eventfd ctx after releasing

The next use of the device will generate an underflow from the
stale reference.

Cc: Qian Cai <[email protected]>
Fixes: 1518ac272e78 ("vfio/pci: fix memory leaks of eventfd ctx")
Reported-by: Daniel Wagner <[email protected]>
Signed-off-by: Alex Williamson <[email protected]>
---
drivers/vfio/pci/vfio_pci.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c
index 7c0779018b1b..f634c81998bb 100644
--- a/drivers/vfio/pci/vfio_pci.c
+++ b/drivers/vfio/pci/vfio_pci.c
@@ -521,10 +521,14 @@ static void vfio_pci_release(void *device_data)
vfio_pci_vf_token_user_add(vdev, -1);
vfio_spapr_pci_eeh_release(vdev->pdev);
vfio_pci_disable(vdev);
- if (vdev->err_trigger)
+ if (vdev->err_trigger) {
eventfd_ctx_put(vdev->err_trigger);
- if (vdev->req_trigger)
+ vdev->err_trigger = NULL;
+ }
+ if (vdev->req_trigger) {
eventfd_ctx_put(vdev->req_trigger);
+ vdev->req_trigger = NULL;
+ }
}

mutex_unlock(&vdev->reflck->lock);

2020-06-16 22:36:42

by Qian Cai

Subject: Re: [PATCH] vfio/pci: Clear error and request eventfd ctx after releasing

> On Jun 16, 2020, at 5:26 PM, Alex Williamson <[email protected]> wrote:
>
> The next use of the device will generate an underflow from the
> stale reference.

Thanks Alex for taking care of this. I suppose my tests were too basic and never able to catch this underflow in the first place.

2020-06-17 05:58:48

by Cornelia Huck

Subject: Re: [PATCH] vfio/pci: Clear error and request eventfd ctx after releasing

On Tue, 16 Jun 2020 15:26:36 -0600
Alex Williamson <[email protected]> wrote:

> The next use of the device will generate an underflow from the
> stale reference.
>
> Cc: Qian Cai <[email protected]>
> Fixes: 1518ac272e78 ("vfio/pci: fix memory leaks of eventfd ctx")
> Reported-by: Daniel Wagner <[email protected]>
> Signed-off-by: Alex Williamson <[email protected]>
> ---
> drivers/vfio/pci/vfio_pci.c | 8 ++++++--
> 1 file changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c
> index 7c0779018b1b..f634c81998bb 100644
> --- a/drivers/vfio/pci/vfio_pci.c
> +++ b/drivers/vfio/pci/vfio_pci.c
> @@ -521,10 +521,14 @@ static void vfio_pci_release(void *device_data)
> vfio_pci_vf_token_user_add(vdev, -1);
> vfio_spapr_pci_eeh_release(vdev->pdev);
> vfio_pci_disable(vdev);
> - if (vdev->err_trigger)
> + if (vdev->err_trigger) {
> eventfd_ctx_put(vdev->err_trigger);
> - if (vdev->req_trigger)
> + vdev->err_trigger = NULL;
> + }
> + if (vdev->req_trigger) {
> eventfd_ctx_put(vdev->req_trigger);
> + vdev->req_trigger = NULL;
> + }
> }
>
> mutex_unlock(&vdev->reflck->lock);
>

Clearing this seems like the right thing to do.

Reviewed-by: Cornelia Huck <[email protected]>

2020-06-17 06:53:30

by Daniel Wagner

Subject: Re: [PATCH] vfio/pci: Clear error and request eventfd ctx after releasing

Hi Alex,

On Tue, Jun 16, 2020 at 03:26:36PM -0600, Alex Williamson wrote:
> The next use of the device will generate an underflow from the
> stale reference.
>
> Cc: Qian Cai <[email protected]>
> Fixes: 1518ac272e78 ("vfio/pci: fix memory leaks of eventfd ctx")
> Reported-by: Daniel Wagner <[email protected]>
> Signed-off-by: Alex Williamson <[email protected]>

Thanks for the quick fix. I gave it a try and the warning is gone.

Tested-by: Daniel Wagner <[email protected]>

Thanks,
Daniel