[PATCH nf v2] netfilter: nf_tables: skip expired catchall elements on insert and delete

[PATCH nf v2] netfilter: nf_tables: skip expired catchall elements on insert and delete

[Aohan Mei]

From: Aohan Mei <henrymei@tencent.com>

nft_setelem_catchall_insert() looks up duplicates with
nft_set_elem_active() only, while nft_set_catchall_lookup() and the
dump path additionally skip expired elements.

Once a catchall element with a timeout expires, this predicate drift
makes it invisible to userspace dumps, yet it still blocks
re-insertion: with NLM_F_EXCL the request fails with -EEXIST, and
without it the request reports success but silently inserts nothing.
The stale entry only goes away when the (user-tunable) gc interval
elapses, so the catchall rule may silently stop matching for an
arbitrarily long time after its first expiration.

The delete path shows the same drift: nft_setelem_catchall_deactivate()
picks the first active-next entry in the catchall list, so with an
expired entry still pending GC it retires the stale entry instead of
the fresh one, and it deactivates an element that userspace no longer
sees instead of failing with -ENOENT.

Align both walks with the lookup and dump predicates: only an element
that is active and not expired counts as a duplicate or delete
candidate, using a single timestamp snapshot for the expiry checks.

Reported-by: TencentOS Corvus AI <corvus@tencent.com>
Cc: stable@vger.kernel.org
Fixes: aaa31047a6d2 ("netfilter: nftables: add catch-all set element support")
Assisted-by: CodeBuddy:Kimi-K3
Signed-off-by: Aohan Mei <henrymei@tencent.com>
---
v2: drop the is_dead check, it does not belong to this dedup walk;
    use __nft_set_elem_expired() with a single timestamp snapshot;
    also skip expired catchall elements in the delete path.
v1: https://lore.kernel.org/netfilter-devel/REPLACE-WITH-V1-MESSAGE-ID

 net/netfilter/nf_tables_api.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
index 765a92fa90d6..0f3449cca5d2 100644
--- a/net/netfilter/nf_tables_api.c
+++ b/net/netfilter/nf_tables_api.c
@@ -6991,11 +6991,13 @@ static int nft_setelem_catchall_insert(const struct net *net,
 {
 	struct nft_set_elem_catchall *catchall;
 	u8 genmask = nft_genmask_next(net);
+	u64 tstamp = get_jiffies_64();
 	struct nft_set_ext *ext;
 
 	list_for_each_entry(catchall, &set->catchall_list, list) {
 		ext = nft_set_elem_ext(set, catchall->elem);
-		if (nft_set_elem_active(ext, genmask)) {
+		if (nft_set_elem_active(ext, genmask) &&
+		    !__nft_set_elem_expired(ext, tstamp)) {
 			*priv = catchall->elem;
 			return -EEXIST;
 		}
@@ -7088,11 +7090,13 @@ static int nft_setelem_catchall_deactivate(const struct net *net,
 					   struct nft_set_elem *elem)
 {
 	struct nft_set_elem_catchall *catchall;
+	u64 tstamp = get_jiffies_64();
 	struct nft_set_ext *ext;
 
 	list_for_each_entry(catchall, &set->catchall_list, list) {
 		ext = nft_set_elem_ext(set, catchall->elem);
-		if (!nft_is_active_next(net, ext))
+		if (!nft_is_active_next(net, ext) ||
+		    __nft_set_elem_expired(ext, tstamp))
 			continue;
 
 		kfree(elem->priv);
-- 
2.43.7

Re: [PATCH nf v2] netfilter: nf_tables: skip expired catchall elements on insert and delete

[Pablo Neira Ayuso]

On Thu, Sep 10, 2026 at 04:03:19PM +0800, Aohan Mei wrote:
> From: Aohan Mei <henrymei@tencent.com>
> 
> nft_setelem_catchall_insert() looks up duplicates with
> nft_set_elem_active() only, while nft_set_catchall_lookup() and the
> dump path additionally skip expired elements.
> 
> Once a catchall element with a timeout expires, this predicate drift
> makes it invisible to userspace dumps, yet it still blocks
> re-insertion: with NLM_F_EXCL the request fails with -EEXIST, and
> without it the request reports success but silently inserts nothing.
> The stale entry only goes away when the (user-tunable) gc interval
> elapses, so the catchall rule may silently stop matching for an
> arbitrarily long time after its first expiration.
> 
> The delete path shows the same drift: nft_setelem_catchall_deactivate()
> picks the first active-next entry in the catchall list, so with an
> expired entry still pending GC it retires the stale entry instead of
> the fresh one, and it deactivates an element that userspace no longer
> sees instead of failing with -ENOENT.
> 
> Align both walks with the lookup and dump predicates: only an element
> that is active and not expired counts as a duplicate or delete
> candidate, using a single timestamp snapshot for the expiry checks.
> 
> Reported-by: TencentOS Corvus AI <corvus@tencent.com>
> Cc: stable@vger.kernel.org
> Fixes: aaa31047a6d2 ("netfilter: nftables: add catch-all set element support")
> Assisted-by: CodeBuddy:Kimi-K3
> Signed-off-by: Aohan Mei <henrymei@tencent.com>
> ---
> v2: drop the is_dead check, it does not belong to this dedup walk;
>     use __nft_set_elem_expired() with a single timestamp snapshot;
>     also skip expired catchall elements in the delete path.
> v1: https://lore.kernel.org/netfilter-devel/REPLACE-WITH-V1-MESSAGE-ID
> 
>  net/netfilter/nf_tables_api.c | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
> index 765a92fa90d6..0f3449cca5d2 100644
> --- a/net/netfilter/nf_tables_api.c
> +++ b/net/netfilter/nf_tables_api.c
> @@ -6991,11 +6991,13 @@ static int nft_setelem_catchall_insert(const struct net *net,
>  {
>  	struct nft_set_elem_catchall *catchall;
>  	u8 genmask = nft_genmask_next(net);
> +	u64 tstamp = get_jiffies_64();

No, this does not work. This must use the tstamp that is stored in the
per-netns area.

>  	struct nft_set_ext *ext;
>  
>  	list_for_each_entry(catchall, &set->catchall_list, list) {
>  		ext = nft_set_elem_ext(set, catchall->elem);
> -		if (nft_set_elem_active(ext, genmask)) {
> +		if (nft_set_elem_active(ext, genmask) &&
> +		    !__nft_set_elem_expired(ext, tstamp)) {
>  			*priv = catchall->elem;
>  			return -EEXIST;
>  		}
> @@ -7088,11 +7090,13 @@ static int nft_setelem_catchall_deactivate(const struct net *net,
>  					   struct nft_set_elem *elem)
>  {
>  	struct nft_set_elem_catchall *catchall;
> +	u64 tstamp = get_jiffies_64();
>  	struct nft_set_ext *ext;
>  
>  	list_for_each_entry(catchall, &set->catchall_list, list) {
>  		ext = nft_set_elem_ext(set, catchall->elem);
> -		if (!nft_is_active_next(net, ext))
> +		if (!nft_is_active_next(net, ext) ||
> +		    __nft_set_elem_expired(ext, tstamp))
>  			continue;
>  
>  		kfree(elem->priv);
> -- 
> 2.43.7
>