Re: [PATCH 1/1] tap: fix write-after-free and double free of intr_handle

[David Marchand <david.marchand@redhat.com>]

On Mon, May 2, 2022 at 9:23 PM Quentin Armitage <quentin@armitage.org.uk> wrote:
>
> rte_pmd_tun/tap_probe() allocates pmd->intr_handle in
> eth_dev_tap_create() and it should not be freed until
> rte_pmd_tap_remove() is called.
>
> Inspection of tap_rx_intr_vec_set() shows that the call to
> tap_tx_intr_vec_uninstall() was calling rte_intr_instance_free() but
> tap_tx_intr_vec_install() can then be immediately called, and this then
> uses pmd->intr_handle without it being reallocated.
>
> This commit moves the call of rte_intr_instance_free() from
> tap_tx_intr_vec_uninstall() to rte_pmd_tap_remove().

Good catch.
We want this fix backported:

Fixes: d61138d4f0e2 ("drivers: remove direct access to interrupt handle")
Cc: stable@dpdk.org


>
> Signed-off-by: Quentin Armitage <quentin@armitage.org.uk>
> ---
>  drivers/net/tap/rte_eth_tap.c | 5 +++++
>  drivers/net/tap/tap_intr.c    | 2 --
>  2 files changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/net/tap/rte_eth_tap.c b/drivers/net/tap/rte_eth_tap.c
> index bc3d56a311..aab1692ebf 100644
> --- a/drivers/net/tap/rte_eth_tap.c
> +++ b/drivers/net/tap/rte_eth_tap.c
> @@ -2612,14 +2612,19 @@ static int
>  rte_pmd_tap_remove(struct rte_vdev_device *dev)
>  {
>         struct rte_eth_dev *eth_dev = NULL;
> +       struct pmd_internals *pmd;
> +       struct rte_intr_handle *intr_handle;
>
>         /* find the ethdev entry */
>         eth_dev = rte_eth_dev_allocated(rte_vdev_device_name(dev));
>         if (!eth_dev)
>                 return 0;
>
> +       pmd = eth_dev->data->dev_private;
> +       intr_handle = pmd->intr_handle;
>         tap_dev_close(eth_dev);
>         rte_eth_dev_release_port(eth_dev);
> +       rte_intr_instance_free(intr_handle);

intr_handle is shared for multiprocess, so freeing should happen in
the primary process only.
For this reason, rte_intr_instance_free() should probably go to tap_dev_close.


>
>         return 0;
>  }
> diff --git a/drivers/net/tap/tap_intr.c b/drivers/net/tap/tap_intr.c
> index 56c343acea..a9097def1a 100644
> --- a/drivers/net/tap/tap_intr.c
> +++ b/drivers/net/tap/tap_intr.c
> @@ -34,8 +34,6 @@ tap_rx_intr_vec_uninstall(struct rte_eth_dev *dev)
>         rte_intr_free_epoll_fd(intr_handle);
>         rte_intr_vec_list_free(intr_handle);
>         rte_intr_nb_efd_set(intr_handle, 0);
> -
> -       rte_intr_instance_free(intr_handle);
>  }
>
>  /**
> --
> 2.34.1
>


-- 
David Marchand