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

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Date:   Wed, 17 Jun 2020 07:56:04 +0200
From:   Cornelia Huck <cohuck@...hat.com>
To:     Alex Williamson <alex.williamson@...hat.com>
Cc:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org, dwagner@...e.de,
        cai@....pw
Subject: Re: [PATCH] vfio/pci: Clear error and request eventfd ctx after
 releasing

On Tue, 16 Jun 2020 15:26:36 -0600
Alex Williamson <alex.williamson@...hat.com> wrote:

> The next use of the device will generate an underflow from the
> stale reference.
> 
> Cc: Qian Cai <cai@....pw>
> Fixes: 1518ac272e78 ("vfio/pci: fix memory leaks of eventfd ctx")
> Reported-by: Daniel Wagner <dwagner@...e.de>
> Signed-off-by: Alex Williamson <alex.williamson@...hat.com>
> ---
>  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 <cohuck@...hat.com>