Re: [RFC 2/2] Bluetooth: HCI: Use bt_skb_pull to parse events

[Luiz Augusto von Dentz <luiz.dentz@gmail.com>]

Hi Marcel,

On Tue, Apr 13, 2021 at 12:08 PM Marcel Holtmann <marcel@holtmann.org> wrote:
>
> Hi Luiz,
>
> > This uses bt_skb_pull to check the events received have the minimum
> > required length, while at it also rework checks for flexible arrays to
> > use flex_array_size.
> >
> > Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
> > ---
> > include/net/bluetooth/hci.h |  59 ++-
> > net/bluetooth/hci_event.c   | 848 ++++++++++++++++++++++++++++--------
> > 2 files changed, 722 insertions(+), 185 deletions(-)
> >
> > diff --git a/include/net/bluetooth/hci.h b/include/net/bluetooth/hci.h
> > index ea4ae551c426..13b7c7747bd1 100644
> > --- a/include/net/bluetooth/hci.h
> > +++ b/include/net/bluetooth/hci.h
> > @@ -1894,6 +1894,10 @@ struct hci_cp_le_reject_cis {
> > } __packed;
> >
> > /* ---- HCI Events ---- */
> > +struct hci_ev_status {
> > +     __u8    status;
> > +} __packed;
> > +
> > #define HCI_EV_INQUIRY_COMPLETE               0x01
> >
> > #define HCI_EV_INQUIRY_RESULT         0x02
> > @@ -1906,6 +1910,11 @@ struct inquiry_info {
> >       __le16   clock_offset;
> > } __packed;
> >
> > +struct hci_ev_inquiry_result {
> > +     __u8    num;
> > +     struct inquiry_info info[];
> > +};
> > +
> > #define HCI_EV_CONN_COMPLETE          0x03
> > struct hci_ev_conn_complete {
> >       __u8     status;
> > @@ -2017,7 +2026,7 @@ struct hci_comp_pkts_info {
> > } __packed;
> >
> > struct hci_ev_num_comp_pkts {
> > -     __u8     num_hndl;
> > +     __u8     num;
> >       struct hci_comp_pkts_info handles[];
> > } __packed;
> >
> > @@ -2067,7 +2076,7 @@ struct hci_ev_pscan_rep_mode {
> > } __packed;
> >
> > #define HCI_EV_INQUIRY_RESULT_WITH_RSSI       0x22
> > -struct inquiry_info_with_rssi {
> > +struct inquiry_info_rssi {
> >       bdaddr_t bdaddr;
> >       __u8     pscan_rep_mode;
> >       __u8     pscan_period_mode;
> > @@ -2075,7 +2084,7 @@ struct inquiry_info_with_rssi {
> >       __le16   clock_offset;
> >       __s8     rssi;
> > } __packed;
> > -struct inquiry_info_with_rssi_and_pscan_mode {
> > +struct inquiry_info_rssi_pscan {
> >       bdaddr_t bdaddr;
> >       __u8     pscan_rep_mode;
> >       __u8     pscan_period_mode;
> > @@ -2084,6 +2093,14 @@ struct inquiry_info_with_rssi_and_pscan_mode {
> >       __le16   clock_offset;
> >       __s8     rssi;
> > } __packed;
> > +struct hci_ev_inquiry_result_rssi {
> > +     __u8     num;
> > +     struct inquiry_info_rssi info[];
> > +} __packed;
> > +struct hci_ev_inquiry_result_rssi_pscan {
> > +     __u8     num;
> > +     struct inquiry_info_rssi_pscan info[];
> > +} __packed;
> >
> > #define HCI_EV_REMOTE_EXT_FEATURES    0x23
> > struct hci_ev_remote_ext_features {
> > @@ -2138,6 +2155,11 @@ struct extended_inquiry_info {
> >       __u8     data[240];
> > } __packed;
> >
> > +struct hci_ev_ext_inquiry_result {
> > +     __u8     num;
> > +     struct extended_inquiry_info info[];
> > +} __packed;
> > +
> > #define HCI_EV_KEY_REFRESH_COMPLETE   0x30
> > struct hci_ev_key_refresh_complete {
> >       __u8    status;
> > @@ -2305,13 +2327,18 @@ struct hci_ev_le_conn_complete {
> >
> > #define HCI_EV_LE_ADVERTISING_REPORT  0x02
> > struct hci_ev_le_advertising_info {
> > -     __u8     evt_type;
> > +     __u8     type;
> >       __u8     bdaddr_type;
> >       bdaddr_t bdaddr;
> >       __u8     length;
> >       __u8     data[];
> > } __packed;
> >
> > +struct hci_ev_le_advertising_report {
> > +     __u8    num;
> > +     struct hci_ev_le_advertising_info info[];
> > +} __packed;
> > +
> > #define HCI_EV_LE_CONN_UPDATE_COMPLETE        0x03
> > struct hci_ev_le_conn_update_complete {
> >       __u8     status;
> > @@ -2355,7 +2382,7 @@ struct hci_ev_le_data_len_change {
> >
> > #define HCI_EV_LE_DIRECT_ADV_REPORT   0x0B
> > struct hci_ev_le_direct_adv_info {
> > -     __u8     evt_type;
> > +     __u8     type;
>
> these changes look unrelated. Prepare to send a prepare patch.

Yep, I might split the changes so I make each event into a separate
patch since some changes require some changes in the struct (or just
simplify the naming).

>
> >       __u8     bdaddr_type;
> >       bdaddr_t bdaddr;
> >       __u8     direct_addr_type;
> > @@ -2363,6 +2390,11 @@ struct hci_ev_le_direct_adv_info {
> >       __s8     rssi;
> > } __packed;
> >
> > +struct hci_ev_le_direct_adv_report {
> > +     __u8     num;
> > +     struct hci_ev_le_direct_adv_info info[];
> > +} __packed;
> > +
> > #define HCI_EV_LE_PHY_UPDATE_COMPLETE 0x0c
> > struct hci_ev_le_phy_update_complete {
> >       __u8  status;
> > @@ -2372,8 +2404,8 @@ struct hci_ev_le_phy_update_complete {
> > } __packed;
> >
> > #define HCI_EV_LE_EXT_ADV_REPORT    0x0d
> > -struct hci_ev_le_ext_adv_report {
> > -     __le16   evt_type;
> > +struct hci_ev_le_ext_adv_info {
> > +     __le16   type;
> >       __u8     bdaddr_type;
> >       bdaddr_t bdaddr;
> >       __u8     primary_phy;
> > @@ -2381,11 +2413,16 @@ struct hci_ev_le_ext_adv_report {
> >       __u8     sid;
> >       __u8     tx_power;
> >       __s8     rssi;
> > -     __le16   interval;
> > -     __u8     direct_addr_type;
> > +     __le16   interval;
> > +     __u8     direct_addr_type;
> >       bdaddr_t direct_addr;
> > -     __u8     length;
> > -     __u8     data[];
> > +     __u8     length;
> > +     __u8     data[];
> > +} __packed;
> > +
> > +struct hci_ev_le_ext_adv_report {
> > +     __u8     num;
> > +     struct hci_ev_le_ext_adv_info info[];
> > } __packed;
> >
> > #define HCI_EV_LE_ENHANCED_CONN_COMPLETE    0x0a
> > diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c
> > index 5e99968939ce..db40358521fa 100644
> > --- a/net/bluetooth/hci_event.c
> > +++ b/net/bluetooth/hci_event.c
> > @@ -45,9 +45,16 @@
> > static void hci_cc_inquiry_cancel(struct hci_dev *hdev, struct sk_buff *skb,
> >                                 u8 *new_status)
> > {
> > -     __u8 status = *((__u8 *) skb->data);
> > +     struct hci_ev_status *rp;
> >
> > -     BT_DBG("%s status 0x%2.2x", hdev->name, status);
> > +     rp = bt_skb_pull(skb, sizeof(*rp));
> > +     if (!rp) {
> > +             bt_dev_err(hdev, "Malformed Command Complete: 0x%4.4x",
> > +                        HCI_OP_INQUIRY_CANCEL);
> > +             return;
> > +     }
>
> So you are repeating this over and over again. The error needs to be part of bt_skb_pull and I would make bt_skb_pull static and local to hci_event.c.

Understood, would something like the following make sense:

static void *hci_ev_pull(skb, opcode, size)

The reason I had introduced bt_skb_pull as public function is that it
may be convenient to parse packets in other protocols as well, but I
guess it could be introduced later if we decide to expand this sort of
logic to other protocols as well.

> Regards
>
> Marcel
>


-- 
Luiz Augusto von Dentz