[PATCH 4/5] net: ethernet: mtk_eth_soc: fix flow_offload related refcount bug

Felix Fietkau
2022-11-23T09:58:47Z

Since we call flow_block_cb_decref on FLOW_BLOCK_UNBIND, we need to call
flow_block_cb_incref unconditionally, even for a newly allocated cb.
Fixes a use-after-free bug

Fixes: 502e84e2382d ("net: ethernet: mtk_eth_soc: add flow offloading support")
Signed-off-by: Felix Fietkau <nbd@nbd.name>
---
.../net/ethernet/mediatek/mtk_ppe_offload.c | 21 ++++++++++++-------
1 file changed, 13 insertions(+), 8 deletions(-)

diff --git a/drivers/net/ethernet/mediatek/mtk_ppe_offload.c b/drivers/net/ethernet/mediatek/mtk_ppe_offload.c
index 81afd5ee3fbf..412d215b9571 100644
--- a/drivers/net/ethernet/mediatek/mtk_ppe_offload.c
+++ b/drivers/net/ethernet/mediatek/mtk_ppe_offload.c
@@ -554,6 +554,7 @@ mtk_eth_setup_tc_block(struct net_device *dev, struct flow_block_offload *f)
struct mtk_eth *eth = mac->hw;
static LIST_HEAD(block_cb_list);
struct flow_block_cb *block_cb;
+ bool register_block = false;
flow_setup_cb_t *cb;

if (!eth->soc->offload_version)
@@ -568,16 +569,20 @@ mtk_eth_setup_tc_block(struct net_device *dev, struct flow_block_offload *f)
switch (f->command) {
case FLOW_BLOCK_BIND:
block_cb = flow_block_cb_lookup(f->block, cb, dev);
- if (block_cb) {
- flow_block_cb_incref(block_cb);
- return 0;
+ if (!block_cb) {
+ block_cb = flow_block_cb_alloc(cb, dev, dev, NULL);
+ if (IS_ERR(block_cb))
+ return PTR_ERR(block_cb);
+
+ register_block = true;
}
- block_cb = flow_block_cb_alloc(cb, dev, dev, NULL);
- if (IS_ERR(block_cb))
- return PTR_ERR(block_cb);

- flow_block_cb_add(block_cb, f);
- list_add_tail(&block_cb->driver_list, &block_cb_list);
+ flow_block_cb_incref(block_cb);
+
+ if (register_block) {
+ flow_block_cb_add(block_cb, f);
+ list_add_tail(&block_cb->driver_list, &block_cb_list);
+ }
return 0;
case FLOW_BLOCK_UNBIND:
block_cb = flow_block_cb_lookup(f->block, cb, dev);
--
2.38.1