Hi Patrick,
On Fri, Jan 30, 2015 at 07:46:28AM +0000, Patrick McHardy wrote:
> 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 contexts
>
> Signed-off-by: Patrick McHardy <kaber@xxxxxxxxx>
> ---
> net/netfilter/nft_rbtree.c | 12 +++---------
> 1 file changed, 3 insertions(+), 9 deletions(-)
>
> diff --git a/net/netfilter/nft_rbtree.c b/net/netfilter/nft_rbtree.c
> index 46214f2..417796f 100644
> --- 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;
Good catch.
> 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;
this chunk looks fine to me, we always hold the nfnetlink mutex.
> }
> @@ -190,7 +188,6 @@ static void nft_rbtree_walk(const struct nft_ctx *ctx,
> struct nft_set_elem elem;
> struct rb_node *node;
>
> - spin_lock_bh(&nft_rbtree_lock);
> for (node = rb_first(&priv->root); node != NULL; node = rb_next(node)) {
> if (iter->count < iter->skip)
> goto cont;
> @@ -203,14 +200,11 @@ static void nft_rbtree_walk(const struct nft_ctx *ctx,
> elem.flags = rbe->flags;
>
> iter->err = iter->fn(ctx, set, iter, &elem);
> - if (iter->err < 0) {
> - spin_unlock_bh(&nft_rbtree_lock);
> + if (iter->err < 0)
> return;
> - }
> cont:
> iter->count++;
> }
> - spin_unlock_bh(&nft_rbtree_lock);
> }
>
I think that _walk still needs the lock there. This is called from
nf_tables_dump_set() for each recvmsg() in netlink, and IIRC unlike
rtnetlink the dump path in nfnetlink is lockless.
--
To unsubscribe from this list: send the line "unsubscribe netfilter-devel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
