netfilter: conntrack: use nf_ct_tmpl_free in CT/synproxy error paths

Commit 0838aa7fcfcd ("netfilter: fix netns dependencies with conntrack
templates") migrated templates to the new allocator api, but forgot to
update error paths for them in CT and synproxy to use nf_ct_tmpl_free()
instead of nf_conntrack_free().

Due to that, memory is being freed into the wrong kmemcache, but also
we drop the per net reference count of ct objects causing an imbalance.

In Brad's case, this leads to a wrap-around of net->ct.count and thus
lets __nf_conntrack_alloc() refuse to create a new ct object:

  [   10.340913] xt_addrtype: ipv6 does not support BROADCAST matching
  [   10.810168] nf_conntrack: table full, dropping packet
  [   11.917416] r8169 0000:07:00.0 eth0: link up
  [   11.917438] IPv6: ADDRCONF(NETDEV_CHANGE): eth0: link becomes ready
  [   12.815902] nf_conntrack: table full, dropping packet
  [   15.688561] nf_conntrack: table full, dropping packet
  [   15.689365] nf_conntrack: table full, dropping packet
  [   15.690169] nf_conntrack: table full, dropping packet
  [   15.690967] nf_conntrack: table full, dropping packet
  [...]

With slab debugging, it also reports the wrong kmemcache (kmalloc-512 vs.
nf_conntrack_ffffffff81ce75c0) and reports poison overwrites, etc. Thus,
to fix the problem, export and use nf_ct_tmpl_free() instead.

Fixes: 0838aa7fcfcd ("netfilter: fix netns dependencies with conntrack templates")
Reported-by: Brad Jackson <bjackson0971@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

diff --git a/include/net/netfilter/nf_conntrack.h b/include/net/netfilter/nf_conntrack.h
index 37cd3911d5c59e97fe6328a2852ea17040f4dbc3..4023c4ce260f0ed55ad30907667e2e135ddfde24 100644 (file)
--- a/include/net/netfilter/nf_conntrack.h
+++ b/include/net/netfilter/nf_conntrack.h
@@ -292,6 +292,7 @@ extern unsigned int nf_conntrack_hash_rnd;
 void init_nf_conntrack_hash_rnd(void);
 
 struct nf_conn *nf_ct_tmpl_alloc(struct net *net, u16 zone, gfp_t flags);
+void nf_ct_tmpl_free(struct nf_conn *tmpl);
 
 #define NF_CT_STAT_INC(net, count)       __this_cpu_inc((net)->ct.stat->count)
 #define NF_CT_STAT_INC_ATOMIC(net, count) this_cpu_inc((net)->ct.stat->count)

diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c
index 3c20d02aee738c5293a5b449f28ebff596c7232d..0625a42df108849a9fb2deaaf92037e93a24eb9a 100644 (file)
--- a/net/netfilter/nf_conntrack_core.c
+++ b/net/netfilter/nf_conntrack_core.c
@@ -320,12 +320,13 @@ out_free:
 }
 EXPORT_SYMBOL_GPL(nf_ct_tmpl_alloc);
 
-static void nf_ct_tmpl_free(struct nf_conn *tmpl)
+void nf_ct_tmpl_free(struct nf_conn *tmpl)
 {
        nf_ct_ext_destroy(tmpl);
        nf_ct_ext_free(tmpl);
        kfree(tmpl);
 }
+EXPORT_SYMBOL_GPL(nf_ct_tmpl_free);
 
 static void
 destroy_conntrack(struct nf_conntrack *nfct)

diff --git a/net/netfilter/nf_synproxy_core.c b/net/netfilter/nf_synproxy_core.c
index d7f1685279034b5e3b62748284d24c52cc1f8907..d6ee8f8b19b63aaf30a2a2c9cf8a2a327063e58e 100644 (file)
--- a/net/netfilter/nf_synproxy_core.c
+++ b/net/netfilter/nf_synproxy_core.c
@@ -378,7 +378,7 @@ static int __net_init synproxy_net_init(struct net *net)
 err3:
        free_percpu(snet->stats);
 err2:
-       nf_conntrack_free(ct);
+       nf_ct_tmpl_free(ct);
 err1:
        return err;
 }

diff --git a/net/netfilter/xt_CT.c b/net/netfilter/xt_CT.c
index 43ddeee404e91f97908fb9228c1e873931b75bcc..f3377ce1ff18e8f454ec30af9b5c4be010fd198a 100644 (file)
--- a/net/netfilter/xt_CT.c
+++ b/net/netfilter/xt_CT.c
@@ -233,7 +233,7 @@ out:
        return 0;
 
 err3:
-       nf_conntrack_free(ct);
+       nf_ct_tmpl_free(ct);
 err2:
        nf_ct_l3proto_module_put(par->family);
 err1: