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

[Tim Gardner]

On 4/13/23 6:32 AM, Liming Sun 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;
>   
>   	/* 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;
>   
Acked-by: Tim Gardner <tim.gardner at canonical.com>

Bart has given you a one time pass on this one.
-- 
-----------
Tim Gardner
Canonical, Inc