Commit f02e7dc4 authored by Florian Westphal's avatar Florian Westphal Committed by Pablo Neira Ayuso
Browse files

netfilter: flowtable: prefer refcount_inc 



With refcount_inc_not_zero, we'd also need a smp_rmb or similar,
followed by a test of the CONFIRMED bit.

However, the ct pointer is taken from skb->_nfct, its refcount must
not be 0 (else, we'd already have a use-after-free bug).

Use refcount_inc() instead to clarify the ct refcount is expected to
be at least 1.

Signed-off-by: default avatarFlorian Westphal <fw@strlen.de>
Signed-off-by: default avatarPablo Neira Ayuso <pablo@netfilter.org>
parent 5787db7c

net/netfilter/nf_flow_table_core.c

+3 −8
Original line number Diff line number Diff line
@@ -53,14 +53,14 @@ struct flow_offload *flow_offload_alloc(struct nf_conn *ct) 
{

	struct flow_offload *flow;



	if (unlikely(nf_ct_is_dying(ct) ||

	    !refcount_inc_not_zero(&ct->ct_general.use)))

	if (unlikely(nf_ct_is_dying(ct)))

		return NULL;



	flow = kzalloc(sizeof(*flow), GFP_ATOMIC);

	if (!flow)

		goto err_ct_refcnt;

		return NULL;



	refcount_inc(&ct->ct_general.use);

	flow->ct = ct;



	flow_offload_fill_dir(flow, FLOW_OFFLOAD_DIR_ORIGINAL);
@@ -72,11 +72,6 @@ struct flow_offload *flow_offload_alloc(struct nf_conn *ct) 
		__set_bit(NF_FLOW_DNAT, &flow->flags);



	return flow;



err_ct_refcnt:

	nf_ct_put(ct);



	return NULL;

}

EXPORT_SYMBOL_GPL(flow_offload_alloc);