Return-Path: Content-Type: text/plain; charset=utf-8 Mime-Version: 1.0 (Mac OS X Mail 8.2 \(2098\)) Subject: Re: [PATCH v2] Bluetooth: Fix reporting incorrect EIR in device found mgmt event From: Marcel Holtmann In-Reply-To: <1431600513-6793-1-git-send-email-szymon.janc@tieto.com> Date: Tue, 19 May 2015 21:17:40 +0200 Cc: linux-bluetooth@vger.kernel.org Message-Id: <59B793A7-A4A2-4F52-A942-B0DD9807D660@holtmann.org> References: <1431600513-6793-1-git-send-email-szymon.janc@tieto.com> To: Szymon Janc Sender: linux-bluetooth-owner@vger.kernel.org List-ID: Hi Szymon, > Some remote devices (ie Gigaset G-Tag) misbehave with ADV data length. > This can lead to incorrect EIR format in device found event when > ADV_DATA and SCAN_RSP are merged (terminator field before SCAN_RSP > part). > > Fix this by inspecting ADV_DATA and correct its length if terminator > is found. > >> HCI Event: LE Meta Event (0x3e) plen 42 [hci0] 32.172182 > LE Advertising Report (0x02) > Num reports: 1 > Event type: Connectable undirected - ADV_IND (0x00) > Address type: Public (0x00) > Address: 7C:2F:80:94:97:5A (Gigaset Communications GmbH) > Data length: 30 > Flags: 0x06 > LE General Discoverable Mode > BR/EDR Not Supported > Company: Gigaset Communications GmbH (384) > Data: 021512348094975abbc5 > 16-bit Service UUIDs (partial): 1 entry > Battery Service (0x180f) > RSSI: -65 dBm (0xbf) >> HCI Event: LE Meta Event (0x3e) plen 27 [hci0] 32.172191 > LE Advertising Report (0x02) > Num reports: 1 > Event type: Scan response - SCAN_RSP (0x04) > Address type: Public (0x00) > Address: 7C:2F:80:94:97:5A (Gigaset Communications GmbH) > Data length: 15 > Name (complete): Gigaset G-tag > RSSI: -59 dBm (0xc5) > > Note "Data length: 30" in ADV_DATA which results in 9 extra zero bytes > after Battery Service UUID. Terminator field present in the middle of > EIR in Device Found event resulted in userspace stop parsing EIR and > skipping device name. > > @ Device Found: 7C:2F:80:94:97:5A (1) rssi -59 flags 0x0000 > 02 01 06 0d ff 80 01 02 15 12 34 80 94 97 5a bb ..........4...Z. > c5 03 02 0f 18 00 00 00 00 00 00 00 00 00 0e 09 ................ > 47 69 67 61 73 65 74 20 47 2d 74 61 67 Gigaset G-tag > > With this fix EIR with merged ADV_DATA and SCAN_RSP in device found > event is properly formatted: > > @ Device Found: 7C:2F:80:94:97:5A (1) rssi -59 flags 0x0000 > 02 01 06 0d ff 80 01 02 15 12 34 80 94 97 5a bb ..........4...Z. > c5 03 02 0f 18 0e 09 47 69 67 61 73 65 74 20 47 .......Gigaset G > 2d 74 61 67 -tag > > Signed-off-by: Szymon Janc > --- > v2: fixed build error due to use of non-upstream BT_ERR_RATELIMITED > > net/bluetooth/hci_event.c | 17 +++++++++++++++++ > 1 file changed, 17 insertions(+) > > diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c > index 7b61be7..0407324 100644 > --- a/net/bluetooth/hci_event.c > +++ b/net/bluetooth/hci_event.c > @@ -4711,6 +4711,23 @@ static void process_adv_report(struct hci_dev *hdev, u8 type, bdaddr_t *bdaddr, > struct hci_conn *conn; > bool match; > u32 flags; > + u8 *ptr, real_len; > + > + /* Find the 'real' end of the data in case remote incorrectly > + * set significant part length. I do not understand this sentence. I assume what you want to say find the end of the data in case the report contains padded zero bytes at the end causing an invalid length value. > + */ > + for (ptr = data; ptr < data + len && *ptr; ptr += *ptr + 1) { > + if (ptr + 1 + *ptr > data + len) > + break; > + } I am worried about the unchecked usage of *ptr here. That might let you jump into some memory area. How are we protecting this against malicious advertising data. And we should have mgnt-tester test cases for malicious fields that are not valid data and would make you jump outside of the 31 bytes. > + > + real_len = ptr - data; > + > + /* Adjust for actual length */ > + if (len != real_len) { > + BT_ERR("Corrected invalid ADV_DATA length”); I would spell advertising report data length here. There really is no ADV_DATA anywhere in the specification or used in BlueZ like that. Regards Marcel