Re: [nf PATCH] netfilter: nft_set_rbtree: Add missing expired checks

[Pablo Neira Ayuso <pablo@netfilter.org>]

Hi Phil,

On Wed, May 06, 2020 at 01:11:07PM +0200, Phil Sutter wrote:
> Expired intervals would still match and be dumped to user space until
> garbage collection wiped them out. Make sure they stop matching and
> disappear (from users' perspective) as soon as they expire.
> 
> Fixes: 8d8540c4f5e03 ("netfilter: nft_set_rbtree: add timeout support")
> Signed-off-by: Phil Sutter <phil@nwl.cc>
> ---
>  net/netfilter/nft_set_rbtree.c | 10 ++++++++--
>  1 file changed, 8 insertions(+), 2 deletions(-)
> 
> diff --git a/net/netfilter/nft_set_rbtree.c b/net/netfilter/nft_set_rbtree.c
> index 3ffef454d4699..8efcea03a4cbb 100644
> --- a/net/netfilter/nft_set_rbtree.c
> +++ b/net/netfilter/nft_set_rbtree.c
> @@ -75,7 +75,8 @@ static bool __nft_rbtree_lookup(const struct net *net, const struct nft_set *set
>  		} else if (d > 0)
>  			parent = rcu_dereference_raw(parent->rb_right);
>  		else {
> -			if (!nft_set_elem_active(&rbe->ext, genmask)) {
> +			if (!nft_set_elem_active(&rbe->ext, genmask) ||
> +			    nft_set_elem_expired(&rbe->ext)) {

It seems _insert() does not allow for duplicates. I think it's better
if you just:

        return false;

in case in case the element has expired, right?

Same thing in _get.

Thanks.

>  				parent = rcu_dereference_raw(parent->rb_left);
>  				continue;
>  			}
> @@ -94,6 +95,7 @@ static bool __nft_rbtree_lookup(const struct net *net, const struct nft_set *set
>  
>  	if (set->flags & NFT_SET_INTERVAL && interval != NULL &&
>  	    nft_set_elem_active(&interval->ext, genmask) &&
> +	    !nft_set_elem_expired(&interval->ext) &&
>  	    nft_rbtree_interval_start(interval)) {
>  		*ext = &interval->ext;
>  		return true;
> @@ -149,7 +151,8 @@ static bool __nft_rbtree_get(const struct net *net, const struct nft_set *set,
>  			if (flags & NFT_SET_ELEM_INTERVAL_END)
>  				interval = rbe;
>  		} else {
> -			if (!nft_set_elem_active(&rbe->ext, genmask)) {
> +			if (!nft_set_elem_active(&rbe->ext, genmask) ||
> +			    nft_set_elem_expired(&rbe->ext)) {
>  				parent = rcu_dereference_raw(parent->rb_left);
>  				continue;
>  			}
> @@ -170,6 +173,7 @@ static bool __nft_rbtree_get(const struct net *net, const struct nft_set *set,
>  
>  	if (set->flags & NFT_SET_INTERVAL && interval != NULL &&
>  	    nft_set_elem_active(&interval->ext, genmask) &&
> +	    !nft_set_elem_expired(&interval->ext) &&
>  	    ((!nft_rbtree_interval_end(interval) &&
>  	      !(flags & NFT_SET_ELEM_INTERVAL_END)) ||
>  	     (nft_rbtree_interval_end(interval) &&
> @@ -418,6 +422,8 @@ static void nft_rbtree_walk(const struct nft_ctx *ctx,
>  
>  		if (iter->count < iter->skip)
>  			goto cont;
> +		if (nft_set_elem_expired(&rbe->ext))
> +			goto cont;
>  		if (!nft_set_elem_active(&rbe->ext, iter->genmask))
>  			goto cont;
>  
> -- 
> 2.25.1
>