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

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commit 05907f10e2 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: 22fe54d5fe ("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>
This commit is contained in:
Pablo Neira Ayuso 2022-06-21 14:01:41 +02:00 committed by Greg Kroah-Hartman
parent 85d55a187c
commit 47fbca31ba
1 changed files with 2 additions and 0 deletions
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2
net/netfilter/nft_set_hash.c
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@ -127,6 +127,7 @@ 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;
}
@ -136,6 +137,7 @@ static bool nft_rhash_update(struct nft_set *set, const u32 *key,
err2:
nft_set_elem_destroy(set, he, true);
atomic_dec(&set->nelems);
err1:
return false;
}