svn commit: r194643 - head/sys/kern

[Kip Macy]

On Mon, Jun 22, 2009 at 12:35 PM, Andre Oppermann<andre at freebsd.org> wrote:
> Author: andre
> Date: Mon Jun 22 19:35:39 2009
> New Revision: 194643
> URL: http://svn.freebsd.org/changeset/base/194643
>
> Log:
>  Update m_demote:
>  - remove HT_HEADER test (MT_HEADER == MT_DATA for some time now)
>  - be more pedantic about m_nextpkt in other than first mbuf
>  - update m_flags to be retained
>
> Modified:
>  head/sys/kern/uipc_mbuf.c
>
> Modified: head/sys/kern/uipc_mbuf.c
> ==============================================================================
> --- head/sys/kern/uipc_mbuf.c   Mon Jun 22 19:09:48 2009        (r194642)
> +++ head/sys/kern/uipc_mbuf.c   Mon Jun 22 19:35:39 2009        (r194643)
> @@ -320,11 +320,13 @@ m_demote(struct mbuf *m0, int all)
>                        m->m_flags &= ~M_PKTHDR;
>                        bzero(&m->m_pkthdr, sizeof(struct pkthdr));
>                }
> -               if (m->m_type == MT_HEADER)
> -                       m->m_type = MT_DATA;
> -               if (m != m0 && m->m_nextpkt != NULL)
> +               if (m != m0 && m->m_nextpkt != NULL) {
> +                       KASSERT(m->m_nextpkt == NULL,
> +                           ("%s: m_nextpkt not NULL", __func__));
> +                       m_freem(m->m_nextpkt);
>                        m->m_nextpkt = NULL;
> -               m->m_flags = m->m_flags & (M_EXT|M_EOR|M_RDONLY|M_FREELIST);
> +               }
> +               m->m_flags = m->m_flags & (M_EXT|M_RDONLY|M_FREELIST|M_NOFREE);
>        }
>


Freeing an mbuf that shouldn't be there is not a safe change. You
don't know that m_nextpkt isn't pointing at some random value in
memory and that doing so isn't going to lead to some inexplicable
crash some time later. This is not a good strategy from a support
standpoint.

I've cc'd sam in case he feels differently.


Cheers,
Kip