From: Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx> commit 05907f10e235680cc7fb196810e4ad3215d5e648 upstream. 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: 22fe54d5fefc ("netfilter: nf_tables: add support for dynamic set updates") Signed-off-by: Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- net/netfilter/nft_set_hash.c | 2 ++ 1 file changed, 2 insertions(+) --- a/net/netfilter/nft_set_hash.c +++ b/net/netfilter/nft_set_hash.c @@ -121,6 +121,7 @@ static bool nft_hash_update(struct nft_s /* Another cpu may race to insert the element with the same key */ if (prev) { nft_set_elem_destroy(set, he, true); + atomic_dec(&set->nelems); he = prev; } @@ -130,6 +131,7 @@ out: err2: nft_set_elem_destroy(set, he, true); + atomic_dec(&set->nelems); err1: return false; }