From afe1a28fa9de3f6c5fb2ccfc67c177f7a94caf49 Mon Sep 17 00:00:00 2001 From: Pablo Neira Ayuso Date: Fri, 6 Feb 2026 13:33:43 +0100 Subject: [PATCH] netfilter: nft_set_rbtree: fix bogus EEXIST with NLM_F_CREATE with null interval [ Upstream commit 7f9203f41aae8eea74fba6a3370da41332eabcda ] Userspace adds a non-matching null element to the kernel for historical reasons. This null element is added when the set is populated with elements. Inclusion of this element is conditional, therefore, userspace needs to dump the set content to check for its presence. If the NLM_F_CREATE flag is turned on, this becomes an issue because kernel bogusly reports EEXIST. Add special case to ignore NLM_F_CREATE in this case, therefore, re-adding the nul-element never fails. Fixes: c016c7e45ddf ("netfilter: nf_tables: honor NLM_F_EXCL flag in set element insertion") Signed-off-by: Pablo Neira Ayuso Signed-off-by: Florian Westphal Signed-off-by: Sasha Levin --- net/netfilter/nf_tables_api.c | 5 +++++ net/netfilter/nft_set_rbtree.c | 13 +++++++++++++ 2 files changed, 18 insertions(+) diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c index 42105628d4b9..f10be72021dd 100644 --- a/net/netfilter/nf_tables_api.c +++ b/net/netfilter/nf_tables_api.c @@ -7322,6 +7322,11 @@ static int nft_add_set_elem(struct nft_ctx *ctx, struct nft_set *set, * and an existing one. */ err = -EEXIST; + } else if (err == -ECANCELED) { + /* ECANCELED reports an existing nul-element in + * interval sets. + */ + err = 0; } goto err_element_clash; } diff --git a/net/netfilter/nft_set_rbtree.c b/net/netfilter/nft_set_rbtree.c index b1f04168ec93..0bbce4505b97 100644 --- a/net/netfilter/nft_set_rbtree.c +++ b/net/netfilter/nft_set_rbtree.c @@ -39,6 +39,13 @@ static bool nft_rbtree_interval_start(const struct nft_rbtree_elem *rbe) return !nft_rbtree_interval_end(rbe); } +static bool nft_rbtree_interval_null(const struct nft_set *set, + const struct nft_rbtree_elem *rbe) +{ + return (!memchr_inv(nft_set_ext_key(&rbe->ext), 0, set->klen) && + nft_rbtree_interval_end(rbe)); +} + static int nft_rbtree_cmp(const struct nft_set *set, const struct nft_rbtree_elem *e1, const struct nft_rbtree_elem *e2) @@ -431,6 +438,12 @@ static int __nft_rbtree_insert(const struct net *net, const struct nft_set *set, */ if (rbe_le && !nft_rbtree_cmp(set, new, rbe_le) && nft_rbtree_interval_end(rbe_le) == nft_rbtree_interval_end(new)) { + /* - ignore null interval, otherwise NLM_F_CREATE bogusly + * reports EEXIST. + */ + if (nft_rbtree_interval_null(set, new)) + return -ECANCELED; + *elem_priv = &rbe_le->priv; return -EEXIST; }