On Tue, Sep 06, 2016 at 04:51:17PM +0200, Florian Westphal wrote:
> fgao@xxxxxxxxxx <fgao@xxxxxxxxxx> wrote:
> > From: Gao Feng <fgao@xxxxxxxxxx>
> >
> > When memory is exhausted, nfct_seqadj_ext_add may fail to add the seqadj
> > extension. But the function nf_ct_seqadj_init doesn't check if get valid
> > seqadj pointer by the nfct_seqadj.
> >
> > Now drop the packet directly when fail to add seqadj extension to avoid
> > dereference NULL pointer in nf_ct_seqadj_init.
> >
> > Signed-off-by: Gao Feng <fgao@xxxxxxxxxx>
> > ---
> > v5: Return NF_ACCEPT instead of NF_DROP when nfct_seqadj_ext_add failed in nf_nat_setup_info
> > v4: Drop the packet directly when fail to add seqadj extension;
> > v3: Remove the warning log when seqadj is null;
> > v2: Remove the unnessary seqadj check in nf_ct_seq_adjust
> > v1: Initial patch
> >
> > net/netfilter/nf_conntrack_core.c | 6 +++++-
> > net/netfilter/nf_nat_core.c | 3 ++-
> > 2 files changed, 7 insertions(+), 2 deletions(-)
> >
> > diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c
> > index dd2c43a..dfa76ce 100644
> > --- a/net/netfilter/nf_conntrack_core.c
> > +++ b/net/netfilter/nf_conntrack_core.c
> > @@ -1036,7 +1036,11 @@ init_conntrack(struct net *net, struct nf_conn *tmpl,
> > return (struct nf_conntrack_tuple_hash *)ct;
> >
> > if (tmpl && nfct_synproxy(tmpl)) {
> > - nfct_seqadj_ext_add(ct);
> > + if (!nfct_seqadj_ext_add(ct)) {
> > + nf_conntrack_free(ct);
> > + pr_debug("Can't add seqadj extension\n");
> > + return NULL;
> > + }
>
> if (!nfct_add_synrpxy(ct, tmpl)) {
> nf_conntrack_free(ct);
> return NULL;
> }
>
> static bool nf_ct_add_synproxy(struct nf_conn *ct, const struct nf_conn *tmpl)
> {
> if (tmpl && nfct_synproxy(tmpl)) {
> if (!nfct_seqadj_ext_add(ct))
> return false;
>
> if (!nfct_synproxy_ext_add(ct))
> return false;
> }
>
> return true;
> }
I like this helper idea, please send a v6 using this using what
Florian is proposing.
> > diff --git a/net/netfilter/nf_nat_core.c b/net/netfilter/nf_nat_core.c
> > index de31818..f8b916a 100644
> > --- a/net/netfilter/nf_nat_core.c
> > +++ b/net/netfilter/nf_nat_core.c
> > @@ -441,7 +441,8 @@ nf_nat_setup_info(struct nf_conn *ct,
> > ct->status |= IPS_DST_NAT;
> >
> > if (nfct_help(ct))
> > - nfct_seqadj_ext_add(ct);
> > + if (!nfct_seqadj_ext_add(ct))
> > + return NF_ACCEPT;
> > }
>
> Hmm, why accept?
>
> We are asked to add extension to rewrite sequence numbers, but
> we cannot. How can the connection work if we cannot munge/track
> seqno rewrites?
Actually we could just NF_DROP, but if we add support for ctnetlink to
inject entries with sequence adjustment with no NAT. I think we need
this to get synproxy working with conntrackd state synchronization.
Thanks!
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