[NETFILTER]: nf_conntrack: Fix module refcount dropping too far

If nf_ct_l3proto_find_get() fails to get the refcount of
nf_ct_l3proto_generic, nf_ct_l3proto_put() will drop the refcount
too far.

This gets rid of '.me = THIS_MODULE' of nf_ct_l3proto_generic so that
nf_ct_l3proto_find_get() doesn't try to get refcount of it.
It's OK because its symbol is usable until nf_conntrack.ko is unloaded.

This also kills unnecessary NULL pointer check as well.
__nf_ct_proto_find() allways returns non-NULL pointer.

Signed-off-by: Yasuyuki Kozakai <yasuyuki.kozakai@toshiba.co.jp>
Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/netfilter/nf_conntrack_core.c

@@ -208,10 +208,8 @@ nf_ct_proto_find_get(u_int16_t l3proto, u_int8_t protocol)
 
 	preempt_disable();
 	p = __nf_ct_proto_find(l3proto, protocol);
-	if (p) {
-		if (!try_module_get(p->me))
-			p = &nf_conntrack_generic_protocol;
-	}
+	if (!try_module_get(p->me))
+		p = &nf_conntrack_generic_protocol;
 	preempt_enable();
 
 	return p;
@@ -229,10 +227,8 @@ nf_ct_l3proto_find_get(u_int16_t l3proto)
 
 	preempt_disable();
 	p = __nf_ct_l3proto_find(l3proto);
-	if (p) {
-		if (!try_module_get(p->me))
-			p = &nf_conntrack_generic_l3proto;
-	}
+	if (!try_module_get(p->me))
+		p = &nf_conntrack_generic_l3proto;
 	preempt_enable();
 
 	return p;

net/netfilter/nf_conntrack_l3proto_generic.c

@@ -94,5 +94,4 @@ struct nf_conntrack_l3proto nf_conntrack_generic_l3proto = {
 	.print_conntrack = generic_print_conntrack,
 	.prepare	 = generic_prepare,
 	.get_features	 = generic_get_features,
-	.me		 = THIS_MODULE,
 };