Commit 765da035 authored Jun 21, 2022 by Pablo Neira Ayuso Committed by Greg Kroah-Hartman Jul 07, 2022

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



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: 22fe54d5 ("netfilter: nf_tables: add support for dynamic set updates")
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent eaaa59ae

net/netfilter/nft_set_hash.c

+2 −0

Original line number	Diff line number	Diff line
		@@ -121,6 +121,7 @@ static bool nft_hash_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;
		}

		@@ -130,6 +131,7 @@ static bool nft_hash_update(struct nft_set set, const u32 key,

		err2:
		nft_set_elem_destroy(set, he, true);
		atomic_dec(&set->nelems);
		err1:
		return false;
		}