netfilter: nft_set_pipapo: skip inactive elements during set walk

Otherwise set elements can be deactivated twice which will cause a crash.

Reported-by: Xingyuan Mo <[email protected]>
Fixes: 3c4287f ("nf_tables: Add set type for arbitrary concatenation of ranges")
Signed-off-by: Florian Westphal <[email protected]>
Signed-off-by: Pablo Neira Ayuso <[email protected]>
(backported from commit 317eb96)
[cascardo: context conflict due to missing 0e1ea65]
CVE-2023-6817
Signed-off-by: Thadeu Lima de Souza Cascardo <[email protected]>
Acked-by: Yuxuan Luo <[email protected]>
Acked-by: Thibault Ferrante <[email protected]>
Signed-off-by: Roxana Nicolescu <[email protected]>

Author: Florian Westphal

net/netfilter/nft_set_pipapo.c

@@ -2042,6 +2042,9 @@ static void nft_pipapo_walk(const struct nft_ctx *ctx, struct nft_set *set,
 
 		e = f->mt[r].e;
 
+		if (!nft_set_elem_active(&e->ext, iter->genmask))
+			goto cont;
+
 		elem.priv = e;
 
 		iter->err = iter->fn(ctx, set, iter, &elem);