| Message ID | 20240501042936.2579739-1-iam@sung-woo.kim (mailing list archive) |
|---|---|
| State | Superseded |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | [v2] Bluetooth: L2CAP: Fix div-by-zero in l2cap_le_flowctl_init() | expand |
Hi Sungwoo, On Wed, May 1, 2024 at 12:32 AM Sungwoo Kim <iam@sung-woo.kim> wrote: > > Hi Luiz, could you review this patch? > > This patch prevents a div-by-zero error and potential int overflow by > adding a range check for MTU in hci_cc_le_read_buffer_size() and > hci_cc_le_read_buffer_size_v2(). > Also, hci_connect_le() will refuse to allocate hcon if the MTU is not in > the valid range. > > Bug description: > > l2cap_le_flowctl_init() can cause both div-by-zero and an integer overflow. > > l2cap_le_flowctl_init() > chan->mps = min_t(u16, chan->imtu, chan->conn->mtu - L2CAP_HDR_SIZE); > chan->rx_credits = (chan->imtu / chan->mps) + 1; <- div-by-zero > > Here, chan->conn->mtu could be less than or equal to L2CAP_HDR_SIZE (4). > If mtu is 4, it causes div-by-zero. If mtu is less than 4, it causes an > integer overflow. > > How mtu could have such low value: > > hci_cc_le_read_buffer_size() > hdev->le_mtu = __le16_to_cpu(rp->le_mtu); > > l2cap_conn_add() > conn->mtu = hcon->hdev->le_mtu; > > As shown, mtu is an input from an HCI device. So, any HCI device can > set mtu value to any value, such as lower than 4. > According to the spec v5.4 7.8.2 LE Read Buffer Size command, the value > should be fall in [0x001b, 0xffff]. > > Thank you, > Sungwoo. > > divide error: 0000 [#1] PREEMPT SMP KASAN NOPTI > CPU: 0 PID: 67 Comm: kworker/u5:0 Tainted: G W 6.9.0-rc5+ #20 > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014 > Workqueue: hci0 hci_rx_work > RIP: 0010:l2cap_le_flowctl_init+0x19e/0x3f0 net/bluetooth/l2cap_core.c:547 > Code: e8 17 17 0c 00 66 41 89 9f 84 00 00 00 bf 01 00 00 00 41 b8 02 00 00 00 4c 89 fe 4c 89 e2 89 d9 e8 27 17 0c 00 44 89 f0 31 d2 <66> f7 f3 89 c3 ff c3 4d 8d b7 88 00 00 00 4c 89 f0 48 c1 e8 03 42 > RSP: 0018:ffff88810bc0f858 EFLAGS: 00010246 > RAX: 00000000000002a0 RBX: 0000000000000000 RCX: dffffc0000000000 > RDX: 0000000000000000 RSI: ffff88810bc0f7c0 RDI: ffffc90002dcb66f > RBP: ffff88810bc0f880 R08: aa69db2dda70ff01 R09: 0000ffaaaaaaaaaa > R10: 0084000000ffaaaa R11: 0000000000000000 R12: ffff88810d65a084 > R13: dffffc0000000000 R14: 00000000000002a0 R15: ffff88810d65a000 > FS: 0000000000000000(0000) GS:ffff88811ac00000(0000) knlGS:0000000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > CR2: 0000000020000100 CR3: 0000000103268003 CR4: 0000000000770ef0 > PKRU: 55555554 > Call Trace: > <TASK> > l2cap_le_connect_req net/bluetooth/l2cap_core.c:4902 [inline] > l2cap_le_sig_cmd net/bluetooth/l2cap_core.c:5420 [inline] > l2cap_le_sig_channel net/bluetooth/l2cap_core.c:5486 [inline] > l2cap_recv_frame+0xe59d/0x11710 net/bluetooth/l2cap_core.c:6809 > l2cap_recv_acldata+0x544/0x10a0 net/bluetooth/l2cap_core.c:7506 > hci_acldata_packet net/bluetooth/hci_core.c:3939 [inline] > hci_rx_work+0x5e5/0xb20 net/bluetooth/hci_core.c:4176 > process_one_work kernel/workqueue.c:3254 [inline] > process_scheduled_works+0x90f/0x1530 kernel/workqueue.c:3335 > worker_thread+0x926/0xe70 kernel/workqueue.c:3416 > kthread+0x2e3/0x380 kernel/kthread.c:388 > ret_from_fork+0x5c/0x90 arch/x86/kernel/process.c:147 > ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244 > </TASK> > Modules linked in: > ---[ end trace 0000000000000000 ]--- > > Signed-off-by: Sungwoo Kim <iam@sung-woo.kim> > --- > v1 -> v2: > - Reply with an error code if a given MTU is not valid. > - Refuse hcon allocation if MTU is not still valid. > > include/net/bluetooth/hci.h | 6 ++++++ > net/bluetooth/hci_conn.c | 4 ++++ > net/bluetooth/hci_event.c | 6 ++++++ > 3 files changed, 16 insertions(+) > > diff --git a/include/net/bluetooth/hci.h b/include/net/bluetooth/hci.h > index 5c12761cb..a7bc07e9c 100644 > --- a/include/net/bluetooth/hci.h > +++ b/include/net/bluetooth/hci.h > @@ -1666,6 +1666,12 @@ struct hci_cp_le_set_event_mask { > __u8 mask[8]; > } __packed; > > +/* BLUETOOTH CORE SPECIFICATION Version 5.4 | Vol 4, Part E > + * 7.8.2 LE Read Buffer Size command > + */ > +#define HCI_MIN_LE_MTU 0x001b > +#define HCI_MAX_LE_MTU 0xFFFF Don't think we really need the MAX value here since it is that same as the maximum field can assume so doing x > MAX is sort of useless as it loops around if that happens. > #define HCI_OP_LE_READ_BUFFER_SIZE 0x2002 > struct hci_rp_le_read_buffer_size { > __u8 status; > diff --git a/net/bluetooth/hci_conn.c b/net/bluetooth/hci_conn.c > index 05346250f..0b86a7452 100644 > --- a/net/bluetooth/hci_conn.c > +++ b/net/bluetooth/hci_conn.c > @@ -1277,6 +1277,10 @@ struct hci_conn *hci_connect_le(struct hci_dev *hdev, bdaddr_t *dst, > return ERR_PTR(-EOPNOTSUPP); > } > > + /* Check the mtu is valid */ > + if (hdev->le_mtu < HCI_MIN_LE_MTU || HCI_MAX_LE_MTU < hdev->le_mtu) > + return ERR_PTR(-ECONNREFUSED); > + That probably needs to be done on hci_conn_add if we want to capture both incoming and outgoing. > /* Since the controller supports only one LE connection attempt at a > * time, we return -EBUSY if there is any connection attempt running. > */ > diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c > index 4a27e4a17..a8563cbe2 100644 > --- a/net/bluetooth/hci_event.c > +++ b/net/bluetooth/hci_event.c > @@ -1263,6 +1263,9 @@ static u8 hci_cc_le_read_buffer_size(struct hci_dev *hdev, void *data, > > BT_DBG("%s le mtu %d:%d", hdev->name, hdev->le_mtu, hdev->le_pkts); > > + if (hdev->le_mtu < HCI_MIN_LE_MTU || HCI_MAX_LE_MTU < hdev->le_mtu) > + return HCI_ERROR_INVALID_PARAMETERS; Value 0x00 means 'No dedicated LE Buffer exists. Use the HCI_Read_Buffer_Size command.' so it is not invalid to return it. > return rp->status; > } > > @@ -3821,6 +3824,9 @@ static u8 hci_cc_le_read_buffer_size_v2(struct hci_dev *hdev, void *data, > BT_DBG("%s acl mtu %d:%d iso mtu %d:%d", hdev->name, hdev->acl_mtu, > hdev->acl_pkts, hdev->iso_mtu, hdev->iso_pkts); > > + if (hdev->le_mtu < HCI_MIN_LE_MTU || HCI_MAX_LE_MTU < hdev->le_mtu) > + return HCI_ERROR_INVALID_PARAMETERS; Ditto, this should really be: if (hdev->le_mtu && hdev->le_mtu < HCI_MIN_LE_MTU) > return rp->status; > } > > -- > 2.34.1 >
diff --git a/include/net/bluetooth/hci.h b/include/net/bluetooth/hci.h index 5c12761cb..a7bc07e9c 100644 --- a/include/net/bluetooth/hci.h +++ b/include/net/bluetooth/hci.h @@ -1666,6 +1666,12 @@ struct hci_cp_le_set_event_mask { __u8 mask[8]; } __packed; +/* BLUETOOTH CORE SPECIFICATION Version 5.4 | Vol 4, Part E + * 7.8.2 LE Read Buffer Size command + */ +#define HCI_MIN_LE_MTU 0x001b +#define HCI_MAX_LE_MTU 0xFFFF + #define HCI_OP_LE_READ_BUFFER_SIZE 0x2002 struct hci_rp_le_read_buffer_size { __u8 status; diff --git a/net/bluetooth/hci_conn.c b/net/bluetooth/hci_conn.c index 05346250f..0b86a7452 100644 --- a/net/bluetooth/hci_conn.c +++ b/net/bluetooth/hci_conn.c @@ -1277,6 +1277,10 @@ struct hci_conn *hci_connect_le(struct hci_dev *hdev, bdaddr_t *dst, return ERR_PTR(-EOPNOTSUPP); } + /* Check the mtu is valid */ + if (hdev->le_mtu < HCI_MIN_LE_MTU || HCI_MAX_LE_MTU < hdev->le_mtu) + return ERR_PTR(-ECONNREFUSED); + /* Since the controller supports only one LE connection attempt at a * time, we return -EBUSY if there is any connection attempt running. */ diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c index 4a27e4a17..a8563cbe2 100644 --- a/net/bluetooth/hci_event.c +++ b/net/bluetooth/hci_event.c @@ -1263,6 +1263,9 @@ static u8 hci_cc_le_read_buffer_size(struct hci_dev *hdev, void *data, BT_DBG("%s le mtu %d:%d", hdev->name, hdev->le_mtu, hdev->le_pkts); + if (hdev->le_mtu < HCI_MIN_LE_MTU || HCI_MAX_LE_MTU < hdev->le_mtu) + return HCI_ERROR_INVALID_PARAMETERS; + return rp->status; } @@ -3821,6 +3824,9 @@ static u8 hci_cc_le_read_buffer_size_v2(struct hci_dev *hdev, void *data, BT_DBG("%s acl mtu %d:%d iso mtu %d:%d", hdev->name, hdev->acl_mtu, hdev->acl_pkts, hdev->iso_mtu, hdev->iso_pkts); + if (hdev->le_mtu < HCI_MIN_LE_MTU || HCI_MAX_LE_MTU < hdev->le_mtu) + return HCI_ERROR_INVALID_PARAMETERS; + return rp->status; }
Hi Luiz, could you review this patch? This patch prevents a div-by-zero error and potential int overflow by adding a range check for MTU in hci_cc_le_read_buffer_size() and hci_cc_le_read_buffer_size_v2(). Also, hci_connect_le() will refuse to allocate hcon if the MTU is not in the valid range. Bug description: l2cap_le_flowctl_init() can cause both div-by-zero and an integer overflow. l2cap_le_flowctl_init() chan->mps = min_t(u16, chan->imtu, chan->conn->mtu - L2CAP_HDR_SIZE); chan->rx_credits = (chan->imtu / chan->mps) + 1; <- div-by-zero Here, chan->conn->mtu could be less than or equal to L2CAP_HDR_SIZE (4). If mtu is 4, it causes div-by-zero. If mtu is less than 4, it causes an integer overflow. How mtu could have such low value: hci_cc_le_read_buffer_size() hdev->le_mtu = __le16_to_cpu(rp->le_mtu); l2cap_conn_add() conn->mtu = hcon->hdev->le_mtu; As shown, mtu is an input from an HCI device. So, any HCI device can set mtu value to any value, such as lower than 4. According to the spec v5.4 7.8.2 LE Read Buffer Size command, the value should be fall in [0x001b, 0xffff]. Thank you, Sungwoo. divide error: 0000 [#1] PREEMPT SMP KASAN NOPTI CPU: 0 PID: 67 Comm: kworker/u5:0 Tainted: G W 6.9.0-rc5+ #20 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014 Workqueue: hci0 hci_rx_work RIP: 0010:l2cap_le_flowctl_init+0x19e/0x3f0 net/bluetooth/l2cap_core.c:547 Code: e8 17 17 0c 00 66 41 89 9f 84 00 00 00 bf 01 00 00 00 41 b8 02 00 00 00 4c 89 fe 4c 89 e2 89 d9 e8 27 17 0c 00 44 89 f0 31 d2 <66> f7 f3 89 c3 ff c3 4d 8d b7 88 00 00 00 4c 89 f0 48 c1 e8 03 42 RSP: 0018:ffff88810bc0f858 EFLAGS: 00010246 RAX: 00000000000002a0 RBX: 0000000000000000 RCX: dffffc0000000000 RDX: 0000000000000000 RSI: ffff88810bc0f7c0 RDI: ffffc90002dcb66f RBP: ffff88810bc0f880 R08: aa69db2dda70ff01 R09: 0000ffaaaaaaaaaa R10: 0084000000ffaaaa R11: 0000000000000000 R12: ffff88810d65a084 R13: dffffc0000000000 R14: 00000000000002a0 R15: ffff88810d65a000 FS: 0000000000000000(0000) GS:ffff88811ac00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000020000100 CR3: 0000000103268003 CR4: 0000000000770ef0 PKRU: 55555554 Call Trace: <TASK> l2cap_le_connect_req net/bluetooth/l2cap_core.c:4902 [inline] l2cap_le_sig_cmd net/bluetooth/l2cap_core.c:5420 [inline] l2cap_le_sig_channel net/bluetooth/l2cap_core.c:5486 [inline] l2cap_recv_frame+0xe59d/0x11710 net/bluetooth/l2cap_core.c:6809 l2cap_recv_acldata+0x544/0x10a0 net/bluetooth/l2cap_core.c:7506 hci_acldata_packet net/bluetooth/hci_core.c:3939 [inline] hci_rx_work+0x5e5/0xb20 net/bluetooth/hci_core.c:4176 process_one_work kernel/workqueue.c:3254 [inline] process_scheduled_works+0x90f/0x1530 kernel/workqueue.c:3335 worker_thread+0x926/0xe70 kernel/workqueue.c:3416 kthread+0x2e3/0x380 kernel/kthread.c:388 ret_from_fork+0x5c/0x90 arch/x86/kernel/process.c:147 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244 </TASK> Modules linked in: ---[ end trace 0000000000000000 ]--- Signed-off-by: Sungwoo Kim <iam@sung-woo.kim> --- v1 -> v2: - Reply with an error code if a given MTU is not valid. - Refuse hcon allocation if MTU is not still valid. include/net/bluetooth/hci.h | 6 ++++++ net/bluetooth/hci_conn.c | 4 ++++ net/bluetooth/hci_event.c | 6 ++++++ 3 files changed, 16 insertions(+)