SCO packet reassembler may have a fragment of SCO packet, from previous connection, cached and not removed when SCO connection is ended. Packets from new SCO connection are then going to be attached to that fragment, creating an invalid SCO packets. Controllers like Intel's WilkinsPeak are always fragmenting SCO packet into 3 parts (#1, #2, #3). Packet #1 contains SCO header and audio data, others just audio data. if there is a fragment cached from previous connection, i.e. #1, first SCO packet from new connection is going to be attached to it creating packet consisting of fragments #1-#1-#2. This will be forwarded to upper layers. After that, fragment #3 is going to be used as a starting point for another SCO packet. It does not contain a SCO header, but the code expects it, casts a SCO header structure on it, and reads whatever audio data happens to be there as SCO packet length and handle. >From that point on, we are assembling random data into SCO packets. Usually it recovers quickly as initial audio data contains mostly zeros (muted stream), but setups of over 4 seconds were observed. Issue manifests itself by printing on the console: Bluetooth: hci0 SCO packet for unknown connection handle 48 Bluetooth: hci0 SCO packet for unknown connection handle 2560 Bluetooth: hci0 SCO packet for unknown connection handle 12288 It may also show random handles if audio data was non-zeroed. Hcidump shows SCO packets with random length and handles. Few messages with handle 0 at connection creation are OK for some controllers (like WilkinsPeak), as there are SCO packets with zeroed handle at the beginning (possible controller bug). Few of such messages at connection end, with a handle looking sane (around 256, 512, 768 ...) is also OK, as these are last SCO packets that were assembled and sent up, before connection was ended, but were not handled in time. This issue may still manifest itself on WilkinsPeak as it sometimes, at SCO connection creation, does not send third fragment of first SCO packet (#1-#2-#1-#2-#3...). This is a firmware bug and this patch does not address it. Signed-off-by: Kuba Pawlak <kubax.t.pawlak@xxxxxxxxx> --- drivers/bluetooth/btusb.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/drivers/bluetooth/btusb.c b/drivers/bluetooth/btusb.c index 9521b7bcc22d61b7690a928bc09500c883fe5495..95c1455823dd668c1d9a97da352728fb53f27a4e 100644 --- a/drivers/bluetooth/btusb.c +++ b/drivers/bluetooth/btusb.c @@ -1277,6 +1277,18 @@ static void btusb_work(struct work_struct *work) clear_bit(BTUSB_ISOC_RUNNING, &data->flags); usb_kill_anchored_urbs(&data->isoc_anchor); + /* When isochronous interface settings need to change, because + * SCO connection was added or removed, a packet fragment may + * be left in reassembler. It would then be attached to SCO + * fragments of later SCO connections, in the end creating wrongly + * reassembled SCO stream with packets of random lengths and handles. + * Clear outstanding fragment when interface settings change. + */ + spin_lock(&data->rxlock); + kfree_skb(data->sco_skb); + data->sco_skb = NULL; + spin_unlock(&data->rxlock); + if (__set_isoc_interface(hdev, new_alts) < 0) return; } -- 1.9.3 -- To unsubscribe from this list: send the line "unsubscribe linux-bluetooth" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
