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Subject[PATCH 4.9 09/29] netfilter: nft_dynset: restore set element counter when failing to update
Date
From: Pablo Neira Ayuso <pablo@netfilter.org>

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@netfilter.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
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;
}

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