Re: [Qemu-devel] [PATCH-for-3.1.1 1/1] Fix heap overflow in ip_reass on big packet input

[Marc-André Lureau]

On Fri, Aug 2, 2019 at 10:09 PM Philippe Mathieu-Daudé
<address@hidden> wrote:
>
> From: Samuel Thibault <address@hidden>
>
> When the first fragment does not fit in the preallocated buffer, q will
> already be pointing to the ext buffer, so we mustn't try to update it.
>
> Signed-off-by: Samuel Thibault <address@hidden>
> (cherry picked from libslirp commit 126c04acbabd7ad32c2b018fe10dfac2a3bc1210)
> Fixes: CVE-2019-14378
> Signed-off-by: Philippe Mathieu-Daudé <address@hidden>

Reviewed-by: Marc-André Lureau <address@hidden>


thanks

> ---
>  slirp/ip_input.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/slirp/ip_input.c b/slirp/ip_input.c
> index 348e1dca5a..07d8808671 100644
> --- a/slirp/ip_input.c
> +++ b/slirp/ip_input.c
> @@ -334,6 +334,8 @@ insert:
>      q = fp->frag_link.next;
>         m = dtom(slirp, q);
>
> +       int was_ext = m->m_flags & M_EXT;
> +
>         q = (struct ipasfrag *) q->ipf_next;
>         while (q != (struct ipasfrag*)&fp->frag_link) {
>           struct mbuf *t = dtom(slirp, q);
> @@ -356,7 +358,7 @@ insert:
>          * the old buffer (in the mbuf), so we must point ip
>          * into the new buffer.
>          */
> -       if (m->m_flags & M_EXT) {
> +       if (!was_ext && m->m_flags & M_EXT) {
>           int delta = (char *)q - m->m_dat;
>           q = (struct ipasfrag *)(m->m_ext + delta);
>         }
> --
> 2.20.1
>
>


-- 
Marc-André Lureau