RCU safe comment extension handling

Signed-off-by: Jozsef Kadlecsik <kadlec@blackhole.kfki.hu>

2 files changed, 23 insertions, 12 deletions

diff --git a/kernel/include/linux/netfilter/ipset/ip_set.h b/kernel/include/linux/netfilter/ipset/ip_set.h
index 5c1c6a5..8894904 100644
--- a/kernel/include/linux/netfilter/ipset/ip_set.h
+++ b/kernel/include/linux/netfilter/ipset/ip_set.h
@@ -109,8 +109,13 @@ struct ip_set_counter {
 	atomic64_t packets;
 };
 
+struct ip_set_comment_rcu {
+	struct rcu_head rcu;
+	char str[0];
+};
+
 struct ip_set_comment {
-	char *str;
+	struct ip_set_comment_rcu __rcu *c;
 };
 
 struct ip_set_skbinfo {
diff --git a/kernel/include/linux/netfilter/ipset/ip_set_comment.h b/kernel/include/linux/netfilter/ipset/ip_set_comment.h
index 21217ea..42dce2b 100644
--- a/kernel/include/linux/netfilter/ipset/ip_set_comment.h
+++ b/kernel/include/linux/netfilter/ipset/ip_set_comment.h
@@ -20,37 +20,43 @@ static inline void
 ip_set_init_comment(struct ip_set_comment *comment,
 		    const struct ip_set_ext *ext)
 {
+	struct ip_set_comment_rcu *c = rcu_dereference_protected(comment->c, 1);
 	size_t len = ext->comment ? strlen(ext->comment) : 0;
 
-	if (unlikely(comment->str)) {
-		kfree(comment->str);
-		comment->str = NULL;
+	if (unlikely(c)) {
+		kfree_rcu(c, rcu);
+		rcu_assign_pointer(comment->c, NULL);
 	}
 	if (!len)
 		return;
 	if (unlikely(len > IPSET_MAX_COMMENT_SIZE))
 		len = IPSET_MAX_COMMENT_SIZE;
-	comment->str = kzalloc(len + 1, GFP_ATOMIC);
-	if (unlikely(!comment->str))
+	c = kzalloc(sizeof(*c) + len + 1, GFP_ATOMIC);
+	if (unlikely(!c))
 		return;
-	strlcpy(comment->str, ext->comment, len + 1);
+	strlcpy(c->str, ext->comment, len + 1);
+	rcu_assign_pointer(comment->c, c);
 }
 
 static inline int
 ip_set_put_comment(struct sk_buff *skb, struct ip_set_comment *comment)
 {
-	if (!comment->str)
+	struct ip_set_comment_rcu *c = rcu_dereference_bh(comment->c);
+
+	if (!c)
 		return 0;
-	return nla_put_string(skb, IPSET_ATTR_COMMENT, comment->str);
+	return nla_put_string(skb, IPSET_ATTR_COMMENT, c->str);
 }
 
 static inline void
 ip_set_comment_free(struct ip_set_comment *comment)
 {
-	if (unlikely(!comment->str))
+	struct ip_set_comment_rcu *c = rcu_dereference_bh(comment->c);
+
+	if (unlikely(!c))
 		return;
-	kfree(comment->str);
-	comment->str = NULL;
+	kfree_rcu(c, rcu);
+	rcu_assign_pointer(comment->c, NULL);
 }
 
 #endif