netfilter: nft_rbtree: fix locking

Fix a race condition and unnecessary locking:

* the root rb_node must only be accessed under the lock in nft_rbtree_lookup()
* the lock is not needed in lookup functions in netlink context

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

diff --git a/net/netfilter/nft_rbtree.c b/net/netfilter/nft_rbtree.c
index 46214f245665a0f70138cbd025bb9d1917a7e32f..2c75361077f7e5b903b851f2df09873892f37f7e 100644 (file)
--- a/net/netfilter/nft_rbtree.c
+++ b/net/netfilter/nft_rbtree.c
@@ -37,10 +37,11 @@ static bool nft_rbtree_lookup(const struct nft_set *set,
 {
        const struct nft_rbtree *priv = nft_set_priv(set);
        const struct nft_rbtree_elem *rbe, *interval = NULL;
-       const struct rb_node *parent = priv->root.rb_node;
+       const struct rb_node *parent;
        int d;
 
        spin_lock_bh(&nft_rbtree_lock);
+       parent = priv->root.rb_node;
        while (parent != NULL) {
                rbe = rb_entry(parent, struct nft_rbtree_elem, node);
 
@@ -158,7 +159,6 @@ static int nft_rbtree_get(const struct nft_set *set, struct nft_set_elem *elem)
        struct nft_rbtree_elem *rbe;
        int d;
 
-       spin_lock_bh(&nft_rbtree_lock);
        while (parent != NULL) {
                rbe = rb_entry(parent, struct nft_rbtree_elem, node);
 
@@ -173,11 +173,9 @@ static int nft_rbtree_get(const struct nft_set *set, struct nft_set_elem *elem)
                            !(rbe->flags & NFT_SET_ELEM_INTERVAL_END))
                                nft_data_copy(&elem->data, rbe->data);
                        elem->flags = rbe->flags;
-                       spin_unlock_bh(&nft_rbtree_lock);
                        return 0;
                }
        }
-       spin_unlock_bh(&nft_rbtree_lock);
        return -ENOENT;
 }