Re: [Qemu-devel] [PATCH v1] lsi53c895a: check message length value is valid

[Peter Maydell <peter.maydell@linaro.org>]

On 26 October 2018 at 20:43, P J P <ppandit@redhat.com> wrote:
> From: Prasad J Pandit <pjp@fedoraproject.org>
>
> While writing a message in 'lsi_do_msgin', message length value
> in 'msg_len' could be invalid. Add check to avoid OOB access issue.
>
> Signed-off-by: Prasad J Pandit <pjp@fedoraproject.org>
> ---
>  hw/scsi/lsi53c895a.c | 15 ++++++++++++++-
>  1 file changed, 14 insertions(+), 1 deletion(-)
>
> Update v1: add .post_load routine and an assert() call
>   -> https://lists.gnu.org/archive/html/qemu-devel/2018-10/msg05730.html
>
> diff --git a/hw/scsi/lsi53c895a.c b/hw/scsi/lsi53c895a.c
> index d1e6534311..3a40e62853 100644
> --- a/hw/scsi/lsi53c895a.c
> +++ b/hw/scsi/lsi53c895a.c
> @@ -861,12 +861,13 @@ static void lsi_do_status(LSIState *s)
>
>  static void lsi_do_msgin(LSIState *s)
>  {
> -    int len;
> +    uint8_t len;
>      trace_lsi_do_msgin(s->dbc, s->msg_len);
>      s->sfbr = s->msg[0];
>      len = s->msg_len;
>      if (len > s->dbc)
>          len = s->dbc;
> +    assert(len <= LSI_MAX_MSGIN_LEN);
>      pci_dma_write(PCI_DEVICE(s), s->dnad, s->msg, len);
>      /* Linux drivers rely on the last byte being in the SIDL.  */
>      s->sidl = s->msg[len - 1];

Is it possible to get here with len == 0 ?

thanks
-- PMM