netfilter: nft_dynset: restore set element counter when failing to update

This patch fixes a race condition.

nft_rhash_update() might fail for two reasons:

- Element already exists in the hashtable.
- Another packet won race to insert an entry in the hashtable.

In both cases, new() has already bumped the counter via atomic_add_unless(),
therefore, decrement the set element counter.

Fixes: 22fe54d5fe ("netfilter: nf_tables: add support for dynamic set updates")
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
This commit is contained in:
Pablo Neira Ayuso 2022-06-21 14:01:41 +02:00
parent cb8092d70a
commit 05907f10e2

View File

@ -143,6 +143,7 @@ static bool nft_rhash_update(struct nft_set *set, const u32 *key,
/* Another cpu may race to insert the element with the same key */ /* Another cpu may race to insert the element with the same key */
if (prev) { if (prev) {
nft_set_elem_destroy(set, he, true); nft_set_elem_destroy(set, he, true);
atomic_dec(&set->nelems);
he = prev; he = prev;
} }
@ -152,6 +153,7 @@ out:
err2: err2:
nft_set_elem_destroy(set, he, true); nft_set_elem_destroy(set, he, true);
atomic_dec(&set->nelems);
err1: err1:
return false; return false;
} }