Re: [PULL 08/10] hw/net/can/xlnx-zynqmp-can: fix assertion failures in transfer_fifo()

[Philippe Mathieu-Daudé]

Adding CAN bus maintainers.

On 14/2/23 07:11, Jason Wang wrote:
> From: Qiang Liu <cyruscyliu@gmail.com>
>
> Check fifos before poping data from and pushing data into it.
>
> Fixes: 98e5d7a2b726 ("hw/net/can: Introduce Xilinx ZynqMP CAN controller")
> Resolves: https://gitlab.com/qemu-project/qemu/-/issues/1425
> Resolves: https://gitlab.com/qemu-project/qemu/-/issues/1427
> Reported-by: Qiang Liu <cyruscyliu@gmail.com>
> Signed-off-by: Qiang Liu <cyruscyliu@gmail.com>
> Signed-off-by: Jason Wang <jasowang@redhat.com>
> ---
>   hw/net/can/xlnx-zynqmp-can.c | 9 ++++++++-
>   1 file changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/hw/net/can/xlnx-zynqmp-can.c b/hw/net/can/xlnx-zynqmp-can.c
> index e93e6c5..55d3221 100644
> --- a/hw/net/can/xlnx-zynqmp-can.c
> +++ b/hw/net/can/xlnx-zynqmp-can.c
> @@ -451,6 +451,12 @@ static void transfer_fifo(XlnxZynqMPCANState *s, Fifo32 
> *fifo)
>       }
>   
>       while (!fifo32_is_empty(fifo)) {
> +        if (fifo32_num_used(fifo) < (4 * CAN_FRAME_SIZE)) {
> +            g_autofree char *path = object_get_canonical_path(OBJECT(s));
> +            qemu_log_mask(LOG_GUEST_ERROR, "%s: data left in the fifo is not"
> +                          " enough for transfer.\n", path);
> +            break;

This change looks dubious... Shouldn't this rejected earlier?
Shouldn't we assert(fifo32_num_used(fifo)) >= CAN_FRAME_SIZE here?
Is this really how this works on the hardware?

>           for (i = 0; i < CAN_FRAME_SIZE; i++) {
>               data[i] = fifo32_pop(fifo);
>           }