RE: [PATCH v1 1/1] platform/mellanox: fix potential race in mlxbf-tmfifo driver

[Vadim Pasternak]

> -----Original Message-----
> From: Liming Sun <limings@xxxxxxxxxx>
> Sent: Wednesday, 26 April 2023 17:24
> To: Vadim Pasternak <vadimp@xxxxxxxxxx>; David Thompson
> <davthompson@xxxxxxxxxx>; Hans de Goede <hdegoede@xxxxxxxxxx>;
> Mark Gross <markgross@xxxxxxxxxx>
> Cc: Liming Sun <limings@xxxxxxxxxx>; platform-driver-x86@xxxxxxxxxxxxxxx;
> linux-kernel@xxxxxxxxxxxxxxx
> Subject: [PATCH v1 1/1] platform/mellanox: fix potential race in mlxbf-tmfifo
> driver
> 
> This commit adds memory barrier for the 'vq' update in function
> mlxbf_tmfifo_virtio_find_vqs() to avoid potential race due to out-of-order
> memory write. It also adds barrier for the 'is_ready'
> flag to make sure the initializations are visible before this flag is checked.
> 
> Signed-off-by: Liming Sun <limings@xxxxxxxxxx>

Reviewed-by: Vadim Pasternak <vadimp@xxxxxxxxxx>

> ---
>  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 91a077c35b8b..a79318e90a13 100644
> --- a/drivers/platform/mellanox/mlxbf-tmfifo.c
> +++ b/drivers/platform/mellanox/mlxbf-tmfifo.c
> @@ -784,7 +784,7 @@ 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. */ @@ -980,9 +980,13 @@
> static int mlxbf_tmfifo_virtio_find_vqs(struct virtio_device *vdev,
> 
>  		vq->num_max = vring->num;
> 
> +		vq->priv = vring;
> +
> +		/* Make vq update visible before using it. */
> +		virtio_mb(false);
> +
>  		vqs[i] = vq;
>  		vring->vq = vq;
> -		vq->priv = vring;
>  	}
> 
>  	return 0;
> @@ -1302,6 +1306,9 @@ static int mlxbf_tmfifo_probe(struct
> platform_device *pdev)
> 
>  	mod_timer(&fifo->timer, jiffies + MLXBF_TMFIFO_TIMER_INTERVAL);
> 
> +	/* Make all updates visible before setting the 'is_ready' flag. */
> +	virtio_mb(false);
> +
>  	fifo->is_ready = true;
>  	return 0;
> 
> --
> 2.30.1