On Fri, Sep 09, 2016 at 10:50:21PM +0800, fgao@xxxxxxxxxx wrote:
> From: Gao Feng <fgao@xxxxxxxxxx>
>
> When memory is exhausted, nfct_seqadj_ext_add may fail to add the
> synproxy and seqadj extensions. 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 from
> init_conntrack().
>
> Signed-off-by: Gao Feng <fgao@xxxxxxxxxx>
> ---
> v7: Remove one debug log and revert to NF_DROP again;
> v6: Add one helper function to add synproxy
> 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
>
> include/net/netfilter/nf_conntrack_synproxy.h | 13 +++++++++++++
> net/netfilter/nf_conntrack_core.c | 6 +++---
> net/netfilter/nf_nat_core.c | 3 ++-
> 3 files changed, 18 insertions(+), 4 deletions(-)
>
> diff --git a/include/net/netfilter/nf_conntrack_synproxy.h b/include/net/netfilter/nf_conntrack_synproxy.h
> index 6793614..e8cf825 100644
> --- a/include/net/netfilter/nf_conntrack_synproxy.h
> +++ b/include/net/netfilter/nf_conntrack_synproxy.h
> @@ -27,6 +27,19 @@ static inline struct nf_conn_synproxy *nfct_synproxy_ext_add(struct nf_conn *ct)
> #endif
> }
>
> +static inline 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;
> +}
> +
> struct synproxy_stats {
> unsigned int syn_received;
> unsigned int cookie_invalid;
> diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c
> index dd2c43a..64aabeb 100644
> --- a/net/netfilter/nf_conntrack_core.c
> +++ b/net/netfilter/nf_conntrack_core.c
> @@ -1035,9 +1035,9 @@ init_conntrack(struct net *net, struct nf_conn *tmpl,
> if (IS_ERR(ct))
> return (struct nf_conntrack_tuple_hash *)ct;
>
> - if (tmpl && nfct_synproxy(tmpl)) {
> - nfct_seqadj_ext_add(ct);
> - nfct_synproxy_ext_add(ct);
> + if (!nf_ct_add_synproxy(ct, tmpl)) {
> + nf_conntrack_free(ct);
> + return NULL;
This has to be ERR_PTR(-ENOMEM);
So the packet is dropped.
NULL is used for invalid packets, invalid packets keep going and the
user can drop them via -m state --state INVALID.
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