Commit 9cf94eab authored Aug 31, 2015 by Daniel Borkmann Committed by Pablo Neira Ayuso Sep 01, 2015

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



Commit 0838aa7f ("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: 0838aa7f ("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>

parent a9de9777

include/net/netfilter/nf_conntrack.h

+1 −0

Original line number	Diff line number	Diff line
		@@ -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)

net/netfilter/nf_conntrack_core.c

+2 −1

Original line number	Diff line number	Diff line
		@@ -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)

net/netfilter/nf_synproxy_core.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -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;
		}

net/netfilter/xt_CT.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -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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