[PATCH 5.15 233/245] netfilter: nft_flow_offload: reset dst in route object after setting up flow

Greg Kroah-Hartman
2024-02-27T14:11:39Z

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

[ Upstream commit 9e0f0430389be7696396c62f037be4bf72cf93e3 ]

dst is transferred to the flow object, route object does not own it
anymore. Reset dst in route object, otherwise if flow_offload_add()
fails, error path releases dst twice, leading to a refcount underflow.

Fixes: a3c90f7a2323 ("netfilter: nf_tables: flow offload expression")
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
include/net/netfilter/nf_flow_table.h | 2 +-
net/netfilter/nf_flow_table_core.c | 16 +++++++++++++---
2 files changed, 14 insertions(+), 4 deletions(-)

diff --git a/include/net/netfilter/nf_flow_table.h b/include/net/netfilter/nf_flow_table.h
index 7677aacf72002..dabd84fa3fd36 100644
--- a/include/net/netfilter/nf_flow_table.h
+++ b/include/net/netfilter/nf_flow_table.h
@@ -258,7 +258,7 @@ nf_flow_table_offload_del_cb(struct nf_flowtable *flow_table,
}

void flow_offload_route_init(struct flow_offload *flow,
- const struct nf_flow_route *route);
+ struct nf_flow_route *route);

int flow_offload_add(struct nf_flowtable *flow_table, struct flow_offload *flow);
void flow_offload_refresh(struct nf_flowtable *flow_table,
diff --git a/net/netfilter/nf_flow_table_core.c b/net/netfilter/nf_flow_table_core.c
index 4e0a2d47f6a6b..a213a7cb80435 100644
--- a/net/netfilter/nf_flow_table_core.c
+++ b/net/netfilter/nf_flow_table_core.c
@@ -86,12 +86,22 @@ static u32 flow_offload_dst_cookie(struct flow_offload_tuple *flow_tuple)
return 0;
}

+static struct dst_entry *nft_route_dst_fetch(struct nf_flow_route *route,
+ enum flow_offload_tuple_dir dir)
+{
+ struct dst_entry *dst = route->tuple[dir].dst;
+
+ route->tuple[dir].dst = NULL;
+
+ return dst;
+}
+
static int flow_offload_fill_route(struct flow_offload *flow,
- const struct nf_flow_route *route,
+ struct nf_flow_route *route,
enum flow_offload_tuple_dir dir)
{
struct flow_offload_tuple *flow_tuple = &flow->tuplehash[dir].tuple;
- struct dst_entry *dst = route->tuple[dir].dst;
+ struct dst_entry *dst = nft_route_dst_fetch(route, dir);
int i, j = 0;

switch (flow_tuple->l3proto) {
@@ -145,7 +155,7 @@ static void nft_flow_dst_release(struct flow_offload *flow,
}

void flow_offload_route_init(struct flow_offload *flow,
- const struct nf_flow_route *route)
+ struct nf_flow_route *route)
{
flow_offload_fill_route(flow, route, FLOW_OFFLOAD_DIR_ORIGINAL);
flow_offload_fill_route(flow, route, FLOW_OFFLOAD_DIR_REPLY);
--
2.43.0