Re: [Qemu-devel] [PATCH v4 20/30] ssi-sd: fix buffer overrun on invalid state load

[Peter Maydell]

On 31 March 2014 15:17, Michael S. Tsirkin <address@hidden> wrote:
> CVE-2013-4537
>
> s->arglen is taken from wire and used as idx
> in ssi_sd_transfer().
>
> Validate it before access.
>
> Signed-off-by: Michael S. Tsirkin <address@hidden>
> ---
>  hw/sd/ssi-sd.c | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/hw/sd/ssi-sd.c b/hw/sd/ssi-sd.c
> index 3273c8a..d9c4aee 100644
> --- a/hw/sd/ssi-sd.c
> +++ b/hw/sd/ssi-sd.c
> @@ -230,6 +230,9 @@ static int ssi_sd_load(QEMUFile *f, void *opaque, int 
> version_id)
>      for (i = 0; i < 5; i++)
>          s->response[i] = qemu_get_be32(f);
>      s->arglen = qemu_get_be32(f);
> +    if (s->mode == SSI_SD_CMDARG && s->arglen > ARRAY_SIZE(s->cmdarg)) {
> +        return -EINVAL;
> +    }
>      s->response_pos = qemu_get_be32(f);
>      s->stopping = qemu_get_be32(f);

This is insufficient. You don't sanity check response_pos, which
means it can be used to overrun a buffer in the SSI_SD_RESPONSE
case if it's set to a negative value.

thanks
-- PMM