[PATCH AUTOSEL 4.14 17/34] netfilter: nf_tables: fix leaking object reference count

Sasha Levin
2019-02-13T02:40:23Z

From: Taehee Yoo <ap420073@gmail.com>

[ Upstream commit b91d9036883793122cf6575ca4dfbfbdd201a83d ]

There is no code that decreases the reference count of stateful objects
in error path of the nft_add_set_elem(). this causes a leak of reference
count of stateful objects.

Test commands:
$nft add table ip filter
$nft add counter ip filter c1
$nft add map ip filter m1 { type ipv4_addr : counter \;}
$nft add element ip filter m1 { 1 : c1 }
$nft add element ip filter m1 { 1 : c1 }
$nft delete element ip filter m1 { 1 }
$nft delete counter ip filter c1

Result:
Error: Could not process rule: Device or resource busy
delete counter ip filter c1
^^^^^^^^^^^^^^^^^^^^^^^^^^^^

At the second 'nft add element ip filter m1 { 1 : c1 }', the reference
count of the 'c1' is increased then it tries to insert into the 'm1'. but
the 'm1' already has same element so it returns -EEXIST.
But it doesn't decrease the reference count of the 'c1' in the error path.
Due to a leak of the reference count of the 'c1', the 'c1' can't be
removed by 'nft delete counter ip filter c1'.

Fixes: 8aeff920dcc9 ("netfilter: nf_tables: add stateful object reference to set elements")
Signed-off-by: Taehee Yoo <ap420073@gmail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/netfilter/nf_tables_api.c | 2 ++
1 file changed, 2 insertions(+)

diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
index 623ec29ade26..bf26e27ca456 100644
--- a/net/netfilter/nf_tables_api.c
+++ b/net/netfilter/nf_tables_api.c
@@ -4046,6 +4046,8 @@ static int nft_add_set_elem(struct nft_ctx *ctx, struct nft_set *set,
err5:
kfree(trans);
err4:
+ if (obj)
+ obj->use--;
kfree(elem.priv);
err3:
if (nla[NFTA_SET_ELEM_DATA] != NULL)
--
2.19.1