diff mbox series

[RFC,v1,1/2] Bluetooth: queue ACL packets if no handle is found

Message ID 20200627185320.RFC.v1.1.Icea550bb064a24b89f2217cf19e35b4480a31afd@changeid
State New
Headers show
Series [RFC,v1,1/2] Bluetooth: queue ACL packets if no handle is found | expand

Commit Message

Archie Pusaka June 27, 2020, 10:54 a.m. UTC
From: Archie Pusaka <apusaka@chromium.org>

There is a possibility that an ACL packet is received before we
receive the HCI connect event for the corresponding handle. If this
happens, we discard the ACL packet.

Rather than just ignoring them, this patch provides a queue for
incoming ACL packet without a handle. The queue is processed when
receiving a HCI connection event. If 2 seconds elapsed without
receiving the HCI connection event, assume something bad happened
and discard the queued packet.

Signed-off-by: Archie Pusaka <apusaka@chromium.org>
Reviewed-by: Abhishek Pandit-Subedi <abhishekpandit@chromium.org>

---

 include/net/bluetooth/hci_core.h |  8 +++
 net/bluetooth/hci_core.c         | 84 +++++++++++++++++++++++++++++---
 net/bluetooth/hci_event.c        |  2 +
 3 files changed, 88 insertions(+), 6 deletions(-)

Comments

Alain Michaud July 17, 2020, 1:17 p.m. UTC | #1
Hi Marcel,

On Fri, Jul 17, 2020 at 2:51 AM Marcel Holtmann <marcel@holtmann.org> wrote:
>

> Hi Alain,

>

> > >>> There is a possibility that an ACL packet is received before we

> > >>> receive the HCI connect event for the corresponding handle. If this

> > >>> happens, we discard the ACL packet.

> > >>>

> > >>> Rather than just ignoring them, this patch provides a queue for

> > >>> incoming ACL packet without a handle. The queue is processed when

> > >>> receiving a HCI connection event. If 2 seconds elapsed without

> > >>> receiving the HCI connection event, assume something bad happened

> > >>> and discard the queued packet.

> > >>>

> > >>> Signed-off-by: Archie Pusaka <apusaka@chromium.org>

> > >>> Reviewed-by: Abhishek Pandit-Subedi <abhishekpandit@chromium.org>

> > >>

> > >> so two things up front. I want to hide this behind a HCI_QUIRK_OUT_OF_ORDER_ACL that a transport driver has to set first. Frankly if this kind of out-of-order happens on UART or SDIO transports, then something is obviously going wrong. I have no plan to fix up after a fully serialized transport.

> > >>

> > >> Secondly, if a transport sets HCI_QUIRK_OUT_OF_ORDER_ACL, then I want this off by default. You can enable it via an experimental setting. The reason here is that we have to make it really hard and fail as often as possible so that hardware manufactures and spec writers realize that something is fundamentally broken here.

> > I don't have any objection to making this explicit enable to non serialized transports.  However, I do wonder what the intention is around making this off by default.  We already know there is a race condition between the interupt and bulk endpoints over USB, so this can and does happen.  Hardware manufaturers can't relly do much about this other than trying to pull the interupt endpoint more often, but that's only a workaround, it can't avoid it all together.

> >

> > IMO, this seems like a legitimate fix at the host level and I don't see any obvious benefits to hide this fix under an experimental feature and make it more difficult for the customers and system integrators to discover.

>

> the problem is that this is not a fix. It is papering over a hole and at best a workaround with both eyes closed and hoping for the best. I am not looking forward for the first security researcher to figure out that they have a chance to inject an unencrypted packet since we are waiting 2 seconds for the USB transport to get its act together.

I don't think this is the right characterization but I agree, 2
seconds would be too long, it would ideally be no longer than the USB
polling interval diff.

>

> In addition, I think that Luiz attempt to align with the poll intervals inside the USB transport directly is a cleaner and more self-contained approach. It also reduces the window of opportunity for any attacker since we actually align the USB transport specific intervals with each other.

I'll have to look at Luiz's patch and think through if this really
eliminates the problem.  If may indeed be a more practical approach to
this problem.

>

> Regards

>

> Marcel

>
diff mbox series

Patch

diff --git a/include/net/bluetooth/hci_core.h b/include/net/bluetooth/hci_core.h
index 836dc997ff94..b69ecdd0d15a 100644
--- a/include/net/bluetooth/hci_core.h
+++ b/include/net/bluetooth/hci_core.h
@@ -270,6 +270,9 @@  struct adv_monitor {
 /* Default authenticated payload timeout 30s */
 #define DEFAULT_AUTH_PAYLOAD_TIMEOUT   0x0bb8
 
+/* Time to keep ACL packets without a corresponding handle queued (2s) */
+#define PENDING_ACL_TIMEOUT		msecs_to_jiffies(2000)
+
 struct amp_assoc {
 	__u16	len;
 	__u16	offset;
@@ -538,6 +541,9 @@  struct hci_dev {
 	struct delayed_work	rpa_expired;
 	bdaddr_t		rpa;
 
+	struct delayed_work	remove_pending_acl;
+	struct sk_buff_head	pending_acl_q;
+
 #if IS_ENABLED(CONFIG_BT_LEDS)
 	struct led_trigger	*power_led;
 #endif
@@ -1773,6 +1779,8 @@  void hci_le_start_enc(struct hci_conn *conn, __le16 ediv, __le64 rand,
 void hci_copy_identity_address(struct hci_dev *hdev, bdaddr_t *bdaddr,
 			       u8 *bdaddr_type);
 
+void hci_process_pending_acl(struct hci_dev *hdev, struct hci_conn *conn);
+
 #define SCO_AIRMODE_MASK       0x0003
 #define SCO_AIRMODE_CVSD       0x0000
 #define SCO_AIRMODE_TRANSP     0x0003
diff --git a/net/bluetooth/hci_core.c b/net/bluetooth/hci_core.c
index 7959b851cc63..30780242c267 100644
--- a/net/bluetooth/hci_core.c
+++ b/net/bluetooth/hci_core.c
@@ -1786,6 +1786,7 @@  int hci_dev_do_close(struct hci_dev *hdev)
 	skb_queue_purge(&hdev->rx_q);
 	skb_queue_purge(&hdev->cmd_q);
 	skb_queue_purge(&hdev->raw_q);
+	skb_queue_purge(&hdev->pending_acl_q);
 
 	/* Drop last sent command */
 	if (hdev->sent_cmd) {
@@ -3518,6 +3519,78 @@  static int hci_suspend_notifier(struct notifier_block *nb, unsigned long action,
 	return NOTIFY_STOP;
 }
 
+static void hci_add_pending_acl(struct hci_dev *hdev, struct sk_buff *skb)
+{
+	skb_queue_tail(&hdev->pending_acl_q, skb);
+
+	queue_delayed_work(hdev->workqueue, &hdev->remove_pending_acl,
+			   PENDING_ACL_TIMEOUT);
+}
+
+void hci_process_pending_acl(struct hci_dev *hdev, struct hci_conn *conn)
+{
+	struct sk_buff *skb, *tmp;
+	struct hci_acl_hdr *hdr;
+	u16 handle, flags;
+	bool reset_timer = false;
+
+	skb_queue_walk_safe(&hdev->pending_acl_q, skb, tmp) {
+		hdr = (struct hci_acl_hdr *)skb->data;
+		handle = __le16_to_cpu(hdr->handle);
+		flags  = hci_flags(handle);
+		handle = hci_handle(handle);
+
+		if (handle != conn->handle)
+			continue;
+
+		__skb_unlink(skb, &hdev->pending_acl_q);
+		skb_pull(skb, HCI_ACL_HDR_SIZE);
+
+		l2cap_recv_acldata(conn, skb, flags);
+		reset_timer = true;
+	}
+
+	if (reset_timer)
+		mod_delayed_work(hdev->workqueue, &hdev->remove_pending_acl,
+				 PENDING_ACL_TIMEOUT);
+}
+
+/* Remove the oldest pending ACL, and all pending ACLs with the same handle */
+static void hci_remove_pending_acl(struct work_struct *work)
+{
+	struct hci_dev *hdev;
+	struct sk_buff *skb, *tmp;
+	struct hci_acl_hdr *hdr;
+	u16 handle, oldest_handle;
+
+	hdev = container_of(work, struct hci_dev, remove_pending_acl.work);
+	skb = skb_dequeue(&hdev->pending_acl_q);
+
+	if (!skb)
+		return;
+
+	hdr = (struct hci_acl_hdr *)skb->data;
+	oldest_handle = hci_handle(__le16_to_cpu(hdr->handle));
+	kfree_skb(skb);
+
+	bt_dev_err(hdev, "ACL packet for unknown connection handle %d",
+		   oldest_handle);
+
+	skb_queue_walk_safe(&hdev->pending_acl_q, skb, tmp) {
+		hdr = (struct hci_acl_hdr *)skb->data;
+		handle = hci_handle(__le16_to_cpu(hdr->handle));
+
+		if (handle == oldest_handle) {
+			__skb_unlink(skb, &hdev->pending_acl_q);
+			kfree_skb(skb);
+		}
+	}
+
+	if (!skb_queue_empty(&hdev->pending_acl_q))
+		queue_delayed_work(hdev->workqueue, &hdev->remove_pending_acl,
+				   PENDING_ACL_TIMEOUT);
+}
+
 /* Alloc HCI device */
 struct hci_dev *hci_alloc_dev(void)
 {
@@ -3610,10 +3683,12 @@  struct hci_dev *hci_alloc_dev(void)
 	INIT_WORK(&hdev->suspend_prepare, hci_prepare_suspend);
 
 	INIT_DELAYED_WORK(&hdev->power_off, hci_power_off);
+	INIT_DELAYED_WORK(&hdev->remove_pending_acl, hci_remove_pending_acl);
 
 	skb_queue_head_init(&hdev->rx_q);
 	skb_queue_head_init(&hdev->cmd_q);
 	skb_queue_head_init(&hdev->raw_q);
+	skb_queue_head_init(&hdev->pending_acl_q);
 
 	init_waitqueue_head(&hdev->req_wait_q);
 	init_waitqueue_head(&hdev->suspend_wait_q);
@@ -4662,8 +4737,6 @@  static void hci_acldata_packet(struct hci_dev *hdev, struct sk_buff *skb)
 	struct hci_conn *conn;
 	__u16 handle, flags;
 
-	skb_pull(skb, HCI_ACL_HDR_SIZE);
-
 	handle = __le16_to_cpu(hdr->handle);
 	flags  = hci_flags(handle);
 	handle = hci_handle(handle);
@@ -4678,17 +4751,16 @@  static void hci_acldata_packet(struct hci_dev *hdev, struct sk_buff *skb)
 	hci_dev_unlock(hdev);
 
 	if (conn) {
+		skb_pull(skb, HCI_ACL_HDR_SIZE);
+
 		hci_conn_enter_active_mode(conn, BT_POWER_FORCE_ACTIVE_OFF);
 
 		/* Send to upper protocol */
 		l2cap_recv_acldata(conn, skb, flags);
 		return;
 	} else {
-		bt_dev_err(hdev, "ACL packet for unknown connection handle %d",
-			   handle);
+		hci_add_pending_acl(hdev, skb);
 	}
-
-	kfree_skb(skb);
 }
 
 /* SCO data packet */
diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c
index e060fc9ebb18..108c6c102a6a 100644
--- a/net/bluetooth/hci_event.c
+++ b/net/bluetooth/hci_event.c
@@ -2627,6 +2627,8 @@  static void hci_conn_complete_evt(struct hci_dev *hdev, struct sk_buff *skb)
 			hci_send_cmd(hdev, HCI_OP_CHANGE_CONN_PTYPE, sizeof(cp),
 				     &cp);
 		}
+
+		hci_process_pending_acl(hdev, conn);
 	} else {
 		conn->state = BT_CLOSED;
 		if (conn->type == ACL_LINK)