Re: [Qemu-devel] [PATCH] slirp: check data length while emulating ident function

[Marc-André Lureau]

Hi

On Fri, Jan 11, 2019 at 12:31 PM P J P <address@hidden> wrote:
>
> From: Prasad J Pandit <address@hidden>
>
> While emulating identification protocol, tcp_emu() does not check
> available space in the 'sc_rcv->sb_data' buffer. It could lead to
> heap buffer overflow issue. Add check to avoid it.
>
> Reported-by: Kira <address@hidden>
> Signed-off-by: Prasad J Pandit <address@hidden>
> ---
>  slirp/tcp_subr.c | 5 +++++
>  1 file changed, 5 insertions(+)
>
> diff --git a/slirp/tcp_subr.c b/slirp/tcp_subr.c
> index fa61349cbb..4415801fbb 100644
> --- a/slirp/tcp_subr.c
> +++ b/slirp/tcp_subr.c
> @@ -635,6 +635,11 @@ tcp_emu(struct socket *so, struct mbuf *m)
>                         socklen_t addrlen = sizeof(struct sockaddr_in);
>                         struct sbuf *so_rcv = &so->so_rcv;
>
> +            if (m->m_len > so_rcv->sb_datalen
> +                            - (so_rcv->sb_wptr - so_rcv->sb_data)) {
> +                m_free(m);
> +                return 0;
> +            }

Check looks correct, it should probably return 1.

Is there a reproducer?

>                         memcpy(so_rcv->sb_wptr, m->m_data, m->m_len);
>                         so_rcv->sb_wptr += m->m_len;
>                         so_rcv->sb_rptr += m->m_len;
> --
> 2.20.1
>
>


-- 
Marc-André Lureau