From 86b6471e690c67d4c5a1892993f34e080f1eae9d Mon Sep 17 00:00:00 2001 From: Weiming Shi Date: Mon, 21 Sep 2026 10:08:22 +0800 Subject: [PATCH] netfilter: nft_set_rbtree: skip transaction elements during GC Since nft_set_commit_update() runs set commit callbacks before processing NEWSETELEM transactions, nft_rbtree_gc_scan() can observe elements added by the transaction being committed. The scan records an interval end in rbe_end without checking the element's transaction state. A later, unrelated expired start then moves both elements to the expired list. The synchronous GC queue can free the new end element before the transaction subsequently activates it, causing a use-after-free. Only consider elements that are fully active in both generations. This keeps transaction-state elements out of the GC scan and preserves interval pairing across skipped elements. KASAN reports: BUG: KASAN: slab-use-after-free in nft_setelem_activate nft_setelem_activate net/netfilter/nf_tables_api.c:7047 nf_tables_commit net/netfilter/nf_tables_api.c:11137 Allocated by task 130: nft_set_elem_init net/netfilter/nf_tables_api.c:6794 nft_add_set_elem net/netfilter/nf_tables_api.c:7523 Freed by task 130: nft_trans_gc_trans_free net/netfilter/nf_tables_api.c:10506 rcu_core kernel/rcu/tree.c:2919 Fixes: 1e3b9e1c77fe ("netfilter: nf_tables: call set ops .commit when building new ruleset blob") Reported-by: Assisted-by: LLM Signed-off-by: Weiming Shi Signed-off-by: Pablo Neira Ayuso --- net/netfilter/nft_set_rbtree.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/net/netfilter/nft_set_rbtree.c b/net/netfilter/nft_set_rbtree.c index 9894832281c4..12431b55752f 100644 --- a/net/netfilter/nft_set_rbtree.c +++ b/net/netfilter/nft_set_rbtree.c @@ -900,6 +900,8 @@ static void nft_rbtree_gc_scan(struct nft_set *set) next = rb_next(node); rbe = rb_entry(node, struct nft_rbtree_elem, node); + if (!nft_set_elem_active(&rbe->ext, NFT_GENMASK_ANY)) + continue; /* elements are reversed in the rbtree for historical reasons, * from highest to lowest value, that is why end element is