From dab45060a56a9732b027d2031c1b6100bc75eea2 Mon Sep 17 00:00:00 2001 From: Liping Zhang Date: Sat, 22 Oct 2016 18:51:26 +0800 Subject: [PATCH] netfilter: nf_tables: fix race when create new element in dynset Packets may race when create the new element in nft_hash_update: CPU0 CPU1 lookup_fast - fail lookup_fast - fail new - ok new - ok insert - ok insert - fail(EEXIST) So when race happened, we reuse the existing element. Otherwise, these *racing* packets will not be handled properly. Fixes: 22fe54d5fefc ("netfilter: nf_tables: add support for dynamic set updates") Signed-off-by: Liping Zhang Signed-off-by: Pablo Neira Ayuso --- net/netfilter/nft_set_hash.c | 15 ++++++++++++--- 1 file changed, 12 insertions(+), 3 deletions(-) diff --git a/net/netfilter/nft_set_hash.c b/net/netfilter/nft_set_hash.c index 88d9fc8343e7..a3dface3e6e6 100644 --- a/net/netfilter/nft_set_hash.c +++ b/net/netfilter/nft_set_hash.c @@ -98,7 +98,7 @@ static bool nft_hash_update(struct nft_set *set, const u32 *key, const struct nft_set_ext **ext) { struct nft_hash *priv = nft_set_priv(set); - struct nft_hash_elem *he; + struct nft_hash_elem *he, *prev; struct nft_hash_cmp_arg arg = { .genmask = NFT_GENMASK_ANY, .set = set, @@ -112,9 +112,18 @@ static bool nft_hash_update(struct nft_set *set, const u32 *key, he = new(set, expr, regs); if (he == NULL) goto err1; - if (rhashtable_lookup_insert_key(&priv->ht, &arg, &he->node, - nft_hash_params)) + + prev = rhashtable_lookup_get_insert_key(&priv->ht, &arg, &he->node, + nft_hash_params); + if (IS_ERR(prev)) goto err2; + + /* Another cpu may race to insert the element with the same key */ + if (prev) { + nft_set_elem_destroy(set, he, true); + he = prev; + } + out: *ext = &he->ext; return true;