xfrm: state: silence sparse warnings during netns exit

Silence sparse warnings in xfrm_state_fini:
net/xfrm/xfrm_state.c:3327:9: warning: incorrect type in argument 1 (different address spaces)
net/xfrm/xfrm_state.c:3327:9:    expected struct hlist_head const *h
net/xfrm/xfrm_state.c:3327:9:    got struct hlist_head [noderef] __rcu *state_byseq

Add xfrm_state_deref_netexit() to wrap those calls. The netns is going
away, we don't have to worry about the state_by* pointers being
changed behind our backs.

Signed-off-by: Sabrina Dubroca <[email protected]>
Reviewed-by: Simon Horman <[email protected]>
Signed-off-by: Steffen Klassert <[email protected]>

Author: qsn

net/xfrm/xfrm_state.c

@@ -3316,6 +3316,8 @@ int __net_init xfrm_state_init(struct net *net)
 	return -ENOMEM;
 }
 
+#define xfrm_state_deref_netexit(table) \
+	rcu_dereference_protected((table), true /* netns is going away */)
 void xfrm_state_fini(struct net *net)
 {
 	unsigned int sz;
@@ -3328,17 +3330,17 @@ void xfrm_state_fini(struct net *net)
 	WARN_ON(!list_empty(&net->xfrm.state_all));
 
 	for (i = 0; i <= net->xfrm.state_hmask; i++) {
-		WARN_ON(!hlist_empty(net->xfrm.state_byseq + i));
-		WARN_ON(!hlist_empty(net->xfrm.state_byspi + i));
-		WARN_ON(!hlist_empty(net->xfrm.state_bysrc + i));
-		WARN_ON(!hlist_empty(net->xfrm.state_bydst + i));
+		WARN_ON(!hlist_empty(xfrm_state_deref_netexit(net->xfrm.state_byseq) + i));
+		WARN_ON(!hlist_empty(xfrm_state_deref_netexit(net->xfrm.state_byspi) + i));
+		WARN_ON(!hlist_empty(xfrm_state_deref_netexit(net->xfrm.state_bysrc) + i));
+		WARN_ON(!hlist_empty(xfrm_state_deref_netexit(net->xfrm.state_bydst) + i));
 	}
 
 	sz = (net->xfrm.state_hmask + 1) * sizeof(struct hlist_head);
-	xfrm_hash_free(net->xfrm.state_byseq, sz);
-	xfrm_hash_free(net->xfrm.state_byspi, sz);
-	xfrm_hash_free(net->xfrm.state_bysrc, sz);
-	xfrm_hash_free(net->xfrm.state_bydst, sz);
+	xfrm_hash_free(xfrm_state_deref_netexit(net->xfrm.state_byseq), sz);
+	xfrm_hash_free(xfrm_state_deref_netexit(net->xfrm.state_byspi), sz);
+	xfrm_hash_free(xfrm_state_deref_netexit(net->xfrm.state_bysrc), sz);
+	xfrm_hash_free(xfrm_state_deref_netexit(net->xfrm.state_bydst), sz);
 	free_percpu(net->xfrm.state_cache_input);
 }