Re: [PATCH v3 08/11] esp: don't overflow cmdfifo in get_cmd()

[Philippe Mathieu-Daudé]

On 4/1/21 9:49 AM, Mark Cave-Ayland wrote:
> If the guest tries to read a CDB using DMA and cmdfifo is not empty then it is
> possible to overflow cmdfifo.
> 
> Since this can only occur by issuing deliberately incorrect instruction
> sequences, ensure that the maximum length of the CDB transferred to cmdfifo is
> limited to the available free space within cmdfifo.
> 
> Buglink: https://bugs.launchpad.net/qemu/+bug/1909247
> Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
> ---
>  hw/scsi/esp.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/hw/scsi/esp.c b/hw/scsi/esp.c
> index 7f49522e1d..c547c60395 100644
> --- a/hw/scsi/esp.c
> +++ b/hw/scsi/esp.c
> @@ -243,6 +243,7 @@ static uint32_t get_cmd(ESPState *s, uint32_t maxlen)
>          }
>          if (s->dma_memory_read) {
>              s->dma_memory_read(s->dma_opaque, buf, dmalen);
> +            dmalen = MIN(fifo8_num_free(&s->fifo), dmalen);

Ditto, GUEST_ERRORS?

Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>

>              fifo8_push_all(&s->cmdfifo, buf, dmalen);
>          } else {
>              if (esp_select(s) < 0) {
>