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().
Decrement the set element counter in this case.
Fixes: 22fe54d5fefc ("netfilter: nf_tables: add support for dynamic set updates")
Signed-off-by: Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx>
---
net/netfilter/nft_set_hash.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/net/netfilter/nft_set_hash.c b/net/netfilter/nft_set_hash.c
index df40314de21f..23a5cfbe3855 100644
--- a/net/netfilter/nft_set_hash.c
+++ b/net/netfilter/nft_set_hash.c
@@ -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 */
if (prev) {
nft_set_elem_destroy(set, he, true);
+ atomic_dec(&set->nelems);
he = prev;
}
@@ -151,6 +152,7 @@ static bool nft_rhash_update(struct nft_set *set, const u32 *key,
return true;
err2:
+ atomic_dec(&set->nelems);
nft_set_elem_destroy(set, he, true);
err1:
return false;
--
2.30.2
