netfilter: nat: use atomic bit op to clear the _SRC_NAT_DONE_BIT

We need to clear the IPS_SRC_NAT_DONE_BIT to indicate that the ct has
been removed from nat_bysource table. But unfortunately, we use the
non-atomic bit operation: "ct->status &= ~IPS_NAT_DONE_MASK". So
there's a race condition that we may clear the _DYING_BIT set by
another CPU unexpectedly.

Since we don't care about the IPS_DST_NAT_DONE_BIT, so just using
clear_bit to clear the IPS_SRC_NAT_DONE_BIT is enough.

Also note, this is the last user which use the non-atomic bit operation
to update the confirmed ct->status.

Reported-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Liping Zhang <zlpnobody@gmail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

diff --git a/net/netfilter/nf_nat_core.c b/net/netfilter/nf_nat_core.c
index ef0be32..6c72922 100644 (file)
--- a/net/netfilter/nf_nat_core.c
+++ b/net/netfilter/nf_nat_core.c
@@ -566,7 +566,7 @@ static int nf_nat_proto_clean(struct nf_conn *ct, void *data)
         * Else, when the conntrack is destoyed, nf_nat_cleanup_conntrack()
         * will delete entry from already-freed table.
         */
-       ct->status &= ~IPS_NAT_DONE_MASK;
+       clear_bit(IPS_SRC_NAT_DONE_BIT, &ct->status);
        rhltable_remove(&nf_nat_bysource_table, &ct->nat_bysource,
                        nf_nat_bysource_params);