Bluetooth: Fix calling request callback more than once

In certain circumstances, such as an HCI driver using __hci_cmd_sync_ev
with HCI_EV_CMD_COMPLETE as the expected completion event there is the
chance that hci_event_packet will call hci_req_cmd_complete twice (once
for the explicitly looked after event and another time in the actual
handler of cmd_complete).

In the case of __hci_cmd_sync_ev this introduces a race where the first
call wakes up the blocking __hci_cmd_sync_ev and lets it complete.
However, by the time that a second __hci_cmd_sync_ev call is already in
progress the second hci_req_cmd_complete call (from the previous
operation) will wake up the blocking function prematurely and cause it
to fail, as witnessed by the following log:

[  639.232195] hci_rx_work: hci0 Event packet
[  639.232201] hci_req_cmd_complete: opcode 0xfc8e status 0x00
[  639.232205] hci_sent_cmd_data: hci0 opcode 0xfc8e
[  639.232210] hci_req_sync_complete: hci0 result 0x00
[  639.232220] hci_cmd_complete_evt: hci0 opcode 0xfc8e
[  639.232225] hci_req_cmd_complete: opcode 0xfc8e status 0x00
[  639.232228] __hci_cmd_sync_ev: hci0 end: err 0
[  639.232234] __hci_cmd_sync_ev: hci0
[  639.232238] hci_req_add_ev: hci0 opcode 0xfc8e plen 250
[  639.232242] hci_prepare_cmd: skb len 253
[  639.232246] hci_req_run: length 1
[  639.232250] hci_sent_cmd_data: hci0 opcode 0xfc8e
[  639.232255] hci_req_sync_complete: hci0 result 0x00
[  639.232266] hci_cmd_work: hci0 cmd_cnt 1 cmd queued 1
[  639.232271] __hci_cmd_sync_ev: hci0 end: err 0
[  639.232276] Bluetooth: hci0 sending Intel patch command (0xfc8e) failed (-61)

Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>
Acked-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.co.uk>

1 files changed, 9 insertions, 1 deletions

diff --git a/net/bluetooth/hci_core.c b/net/bluetooth/hci_core.c
index 0176f200ccb0..48e1e0438f3a 100644
--- a/net/bluetooth/hci_core.c
+++ b/net/bluetooth/hci_core.c
@@ -3442,8 +3442,16 @@ void hci_req_cmd_complete(struct hci_dev *hdev, u16 opcode, u8 status)
          */
         if (hdev->sent_cmd) {
                 req_complete = bt_cb(hdev->sent_cmd)->req.complete;
-                if (req_complete)
+
+                if (req_complete) {
+                        /* We must set the complete callback to NULL to
+                         * avoid calling the callback more than once if
+                         * this function gets called again.
+                         */
+                        bt_cb(hdev->sent_cmd)->req.complete = NULL;
+
                         goto call_complete;
+                }
         }
 
         /* Remove all pending commands belonging to this request */