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 <szymon.janc@xxxxxxxxx>
> ---
> 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
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