[PATCH 4/4] netfilter: synproxy: Check oom when adding synproxy and seqadj ct extensions

[Pablo Neira Ayuso]

From: Gao Feng <f...@ikuai8.com>

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 <f...@ikuai8.com>
Signed-off-by: Pablo Neira Ayuso <pa...@netfilter.org>
---
 include/net/netfilter/nf_conntrack_synproxy.h | 14 ++++++++++++++
 net/netfilter/nf_conntrack_core.c             |  6 +++---
 net/netfilter/nf_nat_core.c                   |  3 ++-
 3 files changed, 19 insertions(+), 4 deletions(-)

diff --git a/include/net/netfilter/nf_conntrack_synproxy.h 
b/include/net/netfilter/nf_conntrack_synproxy.h
index 6793614..e693731 100644
--- a/include/net/netfilter/nf_conntrack_synproxy.h
+++ b/include/net/netfilter/nf_conntrack_synproxy.h
@@ -27,6 +27,20 @@ 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..9934b0c 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 ERR_PTR(-ENOMEM);
        }
 
        timeout_ext = tmpl ? nf_ct_timeout_find(tmpl) : NULL;
diff --git a/net/netfilter/nf_nat_core.c b/net/netfilter/nf_nat_core.c
index 19c081e..ecee105 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_DROP;
        }
 
        if (maniptype == NF_NAT_MANIP_SRC) {
-- 
2.1.4