[PATCH] Bluetooth: skip invalid hci_sync_conn_complete_evt

From: Desmond Cheong Zhi Xi
Date: Wed Jul 21 2021 - 06:36:11 EST

Syzbot reported a corrupted list in kobject_add_internal [1]. This
happens when multiple HCI_EV_SYNC_CONN_COMPLETE event packets with
status 0 are sent for the same HCI connection. This causes us to
register the device more than once which corrupts the kset list.

To fix this, in hci_sync_conn_complete_evt, we check whether we're
trying to process the same HCI_EV_SYNC_CONN_COMPLETE event multiple
times for one connection. If that's the case, the event is invalid, so
we skip further processing and exit.

Link: https://syzkaller.appspot.com/bug?extid=66264bf2fd0476be7e6c [1]
Reported-by: syzbot+66264bf2fd0476be7e6c@xxxxxxxxxxxxxxxxxxxxxxxxx
Tested-by: syzbot+66264bf2fd0476be7e6c@xxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Desmond Cheong Zhi Xi <desmondcheongzx@xxxxxxxxx>
net/bluetooth/hci_event.c | 2 ++
1 file changed, 2 insertions(+)

diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c
index 016b2999f219..091a92338492 100644
--- a/net/bluetooth/hci_event.c
+++ b/net/bluetooth/hci_event.c
@@ -4373,6 +4373,8 @@ static void hci_sync_conn_complete_evt(struct hci_dev *hdev,

switch (ev->status) {
case 0x00:
+ if (conn->state == BT_CONNECTED)
+ goto unlock; /* Already connected, event not valid */
conn->handle = __le16_to_cpu(ev->handle);
conn->state = BT_CONNECTED;
conn->type = ev->link_type;