[PATCH v2 1/1] [SRU][J:linux-bluefield][PATCH v2 1/1] UBUNTU: SAUCE: mlxbf-tmfifo: fix potential race

[Bartlomiej Zolnierkiewicz]

On Thu, Apr 13, 2023 at 2:33 PM Liming Sun <limings at nvidia.com> wrote:
>
> BugLink: https://bugs.launchpad.net/bugs/2016039
>
> The fix adds memory barrier for the 'is_ready' flag and the 'vq'
> pointer in mlxbf_tmfifo_virtio_find_vqs() to avoid potential race
> due to out-of-order memory write.
>
> Signed-off-by: Liming Sun <limings at nvidia.com>
> ---
>  drivers/platform/mellanox/mlxbf-tmfifo.c | 11 +++++++++--
>  1 file changed, 9 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/platform/mellanox/mlxbf-tmfifo.c b/drivers/platform/mellanox/mlxbf-tmfifo.c
> index 97956c9c9d4c..19d539fc99ae 100644
> --- a/drivers/platform/mellanox/mlxbf-tmfifo.c
> +++ b/drivers/platform/mellanox/mlxbf-tmfifo.c
> @@ -922,7 +922,7 @@ static void mlxbf_tmfifo_rxtx(struct mlxbf_tmfifo_vring *vring, bool is_rx)
>         fifo = vring->fifo;
>
>         /* Return if vdev is not ready. */
> -       if (!fifo->vdev[devid])
> +       if (!fifo || !fifo->vdev[devid])
>                 return;

Could you please address the v1 review comment from Andrei:

"This change is not mentioned in the git log. Sounds like an additional
patch to me"

?

Is the above change needed for a case when mlxbf_tmfifo_create_vdev() fails?

>         /* Return if another vring is running. */
> @@ -1119,9 +1119,13 @@ static int mlxbf_tmfifo_virtio_find_vqs(struct virtio_device *vdev,
>                         goto error;
>                 }
>
> +               vq->priv = vring;
> +
> +               /* Make vq update visible before using it. */
> +               virtio_mb(false);
> +
>                 vqs[i] = vq;
>                 vring->vq = vq;
> -               vq->priv = vring;
>         }
>
>         return 0;
> @@ -1426,6 +1430,9 @@ static int mlxbf_tmfifo_probe(struct platform_device *pdev)
>
>         mod_timer(&fifo->timer, jiffies + MLXBF_TMFIFO_TIMER_INTERVAL);
>
> +       /* Make all updates visible before the 'is_ready' flag. */
> +       virtio_mb(false);
> +
>         fifo->is_ready = 1;
>         return 0;
>

--
Best regards,
Bartlomiej