[PATCH 4.2 124/258] netfilter: conntrack: use nf_ct_tmpl_free in CT/synproxy error paths

[Greg Kroah-Hartman]

4.2-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Daniel Borkmann <daniel@xxxxxxxxxxxxx>

commit 9cf94eab8b309e8bcc78b41dd1561c75b537dd0b upstream.

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@xxxxxxxxx>
Signed-off-by: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
Signed-off-by: Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 include/net/netfilter/nf_conntrack.h |    1 +
 net/netfilter/nf_conntrack_core.c    |    3 ++-
 net/netfilter/nf_synproxy_core.c     |    2 +-
 net/netfilter/xt_CT.c                |    2 +-
 4 files changed, 5 insertions(+), 3 deletions(-)

--- a/include/net/netfilter/nf_conntrack.h
+++ b/include/net/netfilter/nf_conntrack.h
@@ -292,6 +292,7 @@ extern unsigned int nf_conntrack_hash_rn
 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)
--- 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)
--- 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(
 err3:
 	free_percpu(snet->stats);
 err2:
-	nf_conntrack_free(ct);
+	nf_ct_tmpl_free(ct);
 err1:
 	return err;
 }
--- 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:


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