[PATCH net 1/1] net: bridge: guard local finish against missing port

[Ren Wei <n05ec@lzu.edu.cn>]

From: Nan Li <tonanli66@gmail.com>

The bridge local receive path may be deferred by netfilter and resumed
later. By the time br_handle_local_finish() runs, skb->dev may still be
valid while its bridge port association has already been removed.

br_handle_local_finish() unconditionally looks up the bridge port from
skb->dev and dereferences it for source learning. If the port is no
longer attached to the bridge, the lookup returns NULL and the deferred
local receive path can no longer rely on the port state being present.

Skip the learning step when the bridge port lookup fails. In that case
there is no port state left to learn on, so returning early preserves
the normal behavior for existing ports while avoiding access to stale
state.

Fixes: 8626c56c8279 ("bridge: fix potential use-after-free when hook returns QUEUE or STOLEN verdict")
Cc: stable@kernel.org
Reported-by: Yuan Tan <yuantan098@gmail.com>
Reported-by: Yifan Wu <yifanwucs@gmail.com>
Reported-by: Juefei Pu <tomapufckgml@gmail.com>
Reported-by: Xin Liu <bird@lzu.edu.cn>
Signed-off-by: Nan Li <tonanli66@gmail.com>
Signed-off-by: Ren Wei <n05ec@lzu.edu.cn>
---
 net/bridge/br_input.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/net/bridge/br_input.c b/net/bridge/br_input.c
index 2cbae0f9ae1f..5b0d7450de5f 100644
--- a/net/bridge/br_input.c
+++ b/net/bridge/br_input.c
@@ -247,6 +247,9 @@ static void __br_handle_local_finish(struct sk_buff *skb)
 	struct net_bridge_port *p = br_port_get_rcu(skb->dev);
 	u16 vid = 0;
 
+	if (unlikely(!p))
+		return;
+
 	/* check if vlan is allowed, to avoid spoofing */
 	if ((p->flags & BR_LEARNING) &&
 	    nbp_state_should_learn(p) &&
-- 
2.43.0