[PATCH v4 nf] netfilter: seqadj: Drop the packet directly when fail to add seqadj extension to avoid dereference NULL pointer later

[fgao]

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

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 <f...@ikuai8.com>
---
 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;
+               }
                nfct_synproxy_ext_add(ct);
        }
 
diff --git a/net/netfilter/nf_nat_core.c b/net/netfilter/nf_nat_core.c
index de31818..b82282a 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) {
-- 
1.9.1