Re: [Xen-devel] [PATCH v3 23/25] hw/ipmi: Assert outlen > outpos

[Marc-André Lureau <marcandre.lureau@xxxxxxxxxx>]

Hi

On Wed, Feb 20, 2019 at 2:08 AM Philippe Mathieu-Daudé
<philmd@xxxxxxxxxx> wrote:
>
> A througfull audit show that all time data is added to outbuf[],

througfull? :) thorough?

> 'outlen' is incremented. Then at creation and each time
> continue_send() returns it pass thru check_reset which resets
> 'outpos', thus we always have 'outlen >= outpos'.
> Also due to the check on entry, we know outlen != 0.
> We can then add an assertion on 'outlen > outpos', which will

hmm, I think you could assert 'outlen >= outpos' only. I don't buy
your argument about 'outlen > outpos' (because outlen != 0?)

> helps the next patch to safely convert 'outlen - outpos' as an
> unsigned type (size_t).
>
> Make this assertion explicit by casting 'outlen - outpos' size_t.
>
> Signed-off-by: Philippe Mathieu-Daudé <philmd@xxxxxxxxxx>
> ---
>  hw/ipmi/ipmi_bmc_extern.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/hw/ipmi/ipmi_bmc_extern.c b/hw/ipmi/ipmi_bmc_extern.c
> index bf0b7ee0f5..ca61b04942 100644
> --- a/hw/ipmi/ipmi_bmc_extern.c
> +++ b/hw/ipmi/ipmi_bmc_extern.c
> @@ -107,8 +107,9 @@ static void continue_send(IPMIBmcExtern *ibe)
>          goto check_reset;
>      }
>   send:
> +    assert(ibe->outlen > ibe->outpos);
>      ret = qemu_chr_fe_write(&ibe->chr, ibe->outbuf + ibe->outpos,
> -                            ibe->outlen - ibe->outpos);
> +                            (size_t)(ibe->outlen - ibe->outpos));
>      if (ret > 0) {
>          ibe->outpos += ret;
>      }
> --
> 2.20.1
>

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