[PATCH 4.19 13/58] netfilter: nfnetlink_cthelper: hit EBUSY on updates if size mismatches

Greg Kroah-Hartman
2021-06-08T18:38:55Z

From: Pablo Neira Ayuso <pablo@netfilter.org>

[ Upstream commit 8971ee8b087750a23f3cd4dc55bff2d0303fd267 ]

The private helper data size cannot be updated. However, updates that
contain NFCTH_PRIV_DATA_LEN might bogusly hit EBUSY even if the size is
the same.

Fixes: 12f7a505331e ("netfilter: add user-space connection tracking helper infrastructure")
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/netfilter/nfnetlink_cthelper.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/net/netfilter/nfnetlink_cthelper.c b/net/netfilter/nfnetlink_cthelper.c
index ddcb1b607474..c8b0f1122c44 100644
--- a/net/netfilter/nfnetlink_cthelper.c
+++ b/net/netfilter/nfnetlink_cthelper.c
@@ -381,10 +381,14 @@ static int
nfnl_cthelper_update(const struct nlattr * const tb[],
struct nf_conntrack_helper *helper)
{
+ u32 size;
int ret;

- if (tb[NFCTH_PRIV_DATA_LEN])
- return -EBUSY;
+ if (tb[NFCTH_PRIV_DATA_LEN]) {
+ size = ntohl(nla_get_be32(tb[NFCTH_PRIV_DATA_LEN]));
+ if (size != helper->data_len)
+ return -EBUSY;
+ }

if (tb[NFCTH_POLICY]) {
ret = nfnl_cthelper_update_policy(helper, tb[NFCTH_POLICY]);
--
2.30.2