Affected: Linux

In the Linux kernel, the following vulnerability has been resolved:

Bluetooth: MGMT: Fix UAF of hci_conn_params in add_device_complete

add_device_complete() runs from the hci_cmd_sync_work kworker, which holds only hci_req_sync_lock and *not* hci_dev_lock. It calls hci_conn_params_lookup() and then dereferences the returned object (params->flags) without taking hci_dev_lock:

params = hci_conn_params_lookup(hdev, &cp->addr.bdaddr, le_addr_type(cp->addr.type)); ... device_flags_changed(NULL, hdev, &cp->addr.bdaddr, cp->addr.type, hdev->conn_flags, params ? params->flags : 0);

hci_conn_params_lookup() walks hdev->le_conn_params and is documented to require hdev->lock. A concurrent MGMT_OP_REMOVE_DEVICE (remove_device()), which does run under hci_dev_lock, can call hci_conn_params_free() to list_del() and kfree() the very object the lookup returned, so the subsequent params->flags read touches freed memory [0].

Hold hci_dev_lock() across the hci_conn_params_lookup() and the read of params->flags (and the matching event emission) so the lookup result cannot be freed by a concurrent remove_device() before it is used, honouring the locking contract of hci_conn_params_lookup().

[0]: (trailing page/memory-state dump trimmed) BUG: KASAN: slab-use-after-free in add_device_complete+0x358/0x3d8 net/bluetooth/mgmt.c:7671 Read of size 1 at addr ffff000017ab26c1 by task kworker/u9:8/388

CPU: 1 UID: 0 PID: 388 Comm: kworker/u9:8 Not tainted 7.0.11 #20 PREEMPT…