Linux v5.4.199: Bluetooth: hci_event: Ignore multiple conn complete events

* Linux v5.4.199: Bluetooth: hci_event: Ignore multiple conn complete events
@ 2022-06-24 22:46 John Klug
  2022-06-24 23:45 ` bluez.test.bot
  2022-06-29  6:33 ` Sönke Huster
  0 siblings, 2 replies; 4+ messages in thread
From: John Klug @ 2022-06-24 22:46 UTC (permalink / raw)
  To: Linux-Bluetooth MailingList; +Cc: Sönke Huster

This patch updated for the 5.4.199 kernel on Friday, 24 June 2022 by
John Klug <john.klug@multitech.com>

From: Soenke Huster <soenke.huster@eknoes.de>
Date: Sun, 23 Jan 2022 15:06:24 +0100
Subject: Bluetooth: hci_event: Ignore multiple conn complete events

When one of the three connection complete events is received multiple
times for the same handle, the device is registered multiple times which
leads to memory corruptions. Therefore, consequent events for a single
connection are ignored.

The conn->state can hold different values, therefore HCI_CONN_HANDLE_UNSET
is introduced to identify new connections. To make sure the events do not
contain this or another invalid handle HCI_CONN_HANDLE_MAX and checks
are introduced.

---
 include/net/bluetooth/hci_core.h |  3 ++
 net/bluetooth/hci_conn.c         |  1 +
 net/bluetooth/hci_event.c        | 63 ++++++++++++++++++++++++++++++----------
 3 files changed, 52 insertions(+), 15 deletions(-)

diff -Naru a/include/net/bluetooth/hci_core.h b/include/net/bluetooth/hci_core.h

--- a/include/net/bluetooth/hci_core.h	2022-06-24 09:07:33.521766338 -0500
+++ b/include/net/bluetooth/hci_core.h	2022-06-24 09:16:20.317754010 -0500
@@ -193,6 +193,9 @@
 
 #define HCI_MAX_SHORT_NAME_LENGTH	10
 
+#define HCI_CONN_HANDLE_UNSET		0xffff
+#define HCI_CONN_HANDLE_MAX		0x0eff
+
 /* Min encryption key size to match with SMP */
 #define HCI_MIN_ENC_KEY_SIZE		7
 
diff -Naru a/net/bluetooth/hci_conn.c b/net/bluetooth/hci_conn.c
--- a/net/bluetooth/hci_conn.c	2022-06-24 09:08:47.105764616 -0500
+++ b/net/bluetooth/hci_conn.c	2022-06-24 09:16:20.317754010 -0500
@@ -504,6 +504,7 @@
 
 	bacpy(&conn->dst, dst);
 	bacpy(&conn->src, &hdev->bdaddr);
+	conn->handle = HCI_CONN_HANDLE_UNSET;
 	conn->hdev  = hdev;
 	conn->type  = type;
 	conn->role  = role;
diff -Naru a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c
--- a/net/bluetooth/hci_event.c	2022-06-24 09:09:10.825764061 -0500
+++ b/net/bluetooth/hci_event.c	2022-06-24 09:19:52.017749056 -0500
@@ -2494,6 +2494,11 @@
 	struct hci_ev_conn_complete *ev = (void *) skb->data;
 	struct hci_conn *conn;
 
+	if (__le16_to_cpu(ev->handle) > HCI_CONN_HANDLE_MAX) {
+		BT_DBG("Ignoring HCI_Connection_Complete for invalid handle");
+		return;
+	}
+        
 	BT_DBG("%s", hdev->name);
 
 	hci_dev_lock(hdev);
@@ -2510,6 +2515,17 @@
 		conn->type = SCO_LINK;
 	}
 
+	/* The HCI_Connection_Complete event is only sent once per connection.
+	 * Processing it more than once per connection can corrupt kernel memory.
+	 *
+	 * As the connection handle is set here for the first time, it indicates
+	 * whether the connection is already set up.
+	 */
+	if (conn->handle != HCI_CONN_HANDLE_UNSET) {
+		BT_DBG("Ignoring HCI_Connection_Complete for existing connection");
+		goto unlock;
+	}
+
 	if (!ev->status) {
 		conn->handle = __le16_to_cpu(ev->handle);
 
@@ -4177,6 +4193,11 @@
 	struct hci_ev_sync_conn_complete *ev = (void *) skb->data;
 	struct hci_conn *conn;
 
+	if (__le16_to_cpu(ev->handle) > HCI_CONN_HANDLE_MAX) {
+		BT_DBG("Ignoring HCI_Sync_Conn_Complete event for invalid handle");
+		return;
+	}
+
 	BT_DBG("%s status 0x%2.2x", hdev->name, ev->status);
 
 	hci_dev_lock(hdev);
@@ -4200,23 +4221,19 @@
 			goto unlock;
 	}
 
+	/* The HCI_Synchronous_Connection_Complete event is only sent once per connection.
+	 * Processing it more than once per connection can corrupt kernel memory.
+	 *
+	 * As the connection handle is set here for the first time, it indicates
+	 * whether the connection is already set up.
+	 */
+	if (conn->handle != HCI_CONN_HANDLE_UNSET) {
+	    BT_DBG("Ignoring HCI_Sync_Conn_Complete event for existing connection");
+		goto unlock;
+	}
+
 	switch (ev->status) {
 	case 0x00:
-		/* The synchronous connection complete event should only be
-		 * sent once per new connection. Receiving a successful
-		 * complete event when the connection status is already
-		 * BT_CONNECTED means that the device is misbehaving and sent
-		 * multiple complete event packets for the same new connection.
-		 *
-		 * Registering the device more than once can corrupt kernel
-		 * memory, hence upon detecting this invalid event, we report
-		 * an error and ignore the packet.
-		 */
-		if (conn->state == BT_CONNECTED) {
-			bt_dev_err(hdev, "Ignoring connect complete event for existing connection");
-			goto unlock;
-		}
-
 		conn->handle = __le16_to_cpu(ev->handle);
 		conn->state  = BT_CONNECTED;
 		conn->type   = ev->link_type;
@@ -4985,6 +5002,11 @@
 	struct smp_irk *irk;
 	u8 addr_type;
 
+	if (handle > HCI_CONN_HANDLE_MAX) {
+		BT_DBG("Ignoring HCI_LE_Connection_Complete for invalid handle");
+		return;
+	}
+
 	hci_dev_lock(hdev);
 
 	/* All controllers implicitly stop advertising in the event of a
@@ -5026,6 +5048,17 @@
 		cancel_delayed_work(&conn->le_conn_timeout);
 	}
 
+	/* The HCI_LE_Connection_Complete event is only sent once per connection.
+	 * Processing it more than once per connection can corrupt kernel memory.
+	 *
+	 * As the connection handle is set here for the first time, it indicates
+	 * whether the connection is already set up.
+	 */
+	if (conn->handle != HCI_CONN_HANDLE_UNSET) {
+		BT_DBG("Ignoring HCI_Connection_Complete for existing connection");
+		goto unlock;
+	}
+
 	le_conn_update_addr(conn, bdaddr, bdaddr_type, local_rpa);
 
 	/* Lookup the identity address from the stored connection

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