diff mbox series

[v2,1/2] Bluetooth: Fix not checking advertisement bondaries

Message ID 20201019172529.1179996-1-luiz.dentz@gmail.com (mailing list archive)
State New, archived
Headers show
Series [v2,1/2] Bluetooth: Fix not checking advertisement bondaries | expand

Commit Message

Luiz Augusto von Dentz Oct. 19, 2020, 5:25 p.m. UTC 
From: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>

When receiving advertisements check if the length is actually within
the skb, this also make use of skb_pull to advance on the skb->data
instead of a custom ptr that way skb->len shall always indicates how
much data is remaining and can be used to perform checks if there is
enough data to parse.

Fixes: a2ec905d1e160a33b2e210e45ad30445ef26ce0e ("Bluetooth: fix kernel oops in store_pending_adv_report")
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
---
v2: Fixes rssi parsing.

 net/bluetooth/hci_event.c | 73 ++++++++++++++++++++++++++++++---------
 1 file changed, 56 insertions(+), 17 deletions(-)

Comments

Abhishek Pandit-Subedi Oct. 21, 2020, 4:34 p.m. UTC | #1 
On Mon, Oct 19, 2020 at 10:25 AM Luiz Augusto von Dentz
<luiz.dentz@gmail.com> wrote:
>
> From: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
>
> When receiving advertisements check if the length is actually within
> the skb, this also make use of skb_pull to advance on the skb->data
> instead of a custom ptr that way skb->len shall always indicates how
> much data is remaining and can be used to perform checks if there is
> enough data to parse.
>
> Fixes: a2ec905d1e160a33b2e210e45ad30445ef26ce0e ("Bluetooth: fix kernel oops in store_pending_adv_report")
> Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
> ---
> v2: Fixes rssi parsing.
>
>  net/bluetooth/hci_event.c | 73 ++++++++++++++++++++++++++++++---------
>  1 file changed, 56 insertions(+), 17 deletions(-)

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

---

I cherry-picked this to our 4.19 kernel and ran our LE Health tests on
the Kohaku chromebook (AX201 controller). All tests are passing.
Johan Hedberg Oct. 22, 2020, 8:55 p.m. UTC | #2 
Hi Luiz,

On Mon, Oct 19, 2020, Luiz Augusto von Dentz wrote:
> When receiving advertisements check if the length is actually within
> the skb, this also make use of skb_pull to advance on the skb->data
> instead of a custom ptr that way skb->len shall always indicates how
> much data is remaining and can be used to perform checks if there is
> enough data to parse.
> 
> Fixes: a2ec905d1e160a33b2e210e45ad30445ef26ce0e ("Bluetooth: fix kernel oops in store_pending_adv_report")
> Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
> ---
> v2: Fixes rssi parsing.
> 
>  net/bluetooth/hci_event.c | 73 ++++++++++++++++++++++++++++++---------
>  1 file changed, 56 insertions(+), 17 deletions(-)

Could we get the matching HCI logs for these corrupted events? It'd be
good to include that in the commit message. Unless I misunderstood
something, from what I can see from the changes the fields you are
adding checks for are generated by the Bluetooth controller, i.e. only a
buggy or broken Bluetooth controller would generate such events
(meaning, this shouldn't be generally remotely exploitable), so it'd be
good to know exactly which controllers generate such broken events.

Johan
diff mbox series

Patch

diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c
index a4c3703f2e94..6925c090a9e0 100644
--- a/net/bluetooth/hci_event.c
+++ b/net/bluetooth/hci_event.c
@@ -5599,24 +5599,41 @@  static void process_adv_report(struct hci_dev *hdev, u8 type, bdaddr_t *bdaddr,
 static void hci_le_adv_report_evt(struct hci_dev *hdev, struct sk_buff *skb)
 {
 	u8 num_reports = skb->data[0];
-	void *ptr = &skb->data[1];
 
 	hci_dev_lock(hdev);
 
+	skb_pull(skb, sizeof(num_reports));
+
 	while (num_reports--) {
-		struct hci_ev_le_advertising_info *ev = ptr;
+		struct hci_ev_le_advertising_info *ev;
 		s8 rssi;
 
-		if (ev->length <= HCI_MAX_AD_LENGTH) {
-			rssi = ev->data[ev->length];
-			process_adv_report(hdev, ev->evt_type, &ev->bdaddr,
-					   ev->bdaddr_type, NULL, 0, rssi,
-					   ev->data, ev->length, false);
-		} else {
-			bt_dev_err(hdev, "Dropping invalid advertising data");
+		if (skb->len < sizeof(*ev)) {
+			bt_dev_err(hdev, "Malformed advertising report");
+			break;
+		}
+
+		ev = (void *) skb->data;
+		skb_pull(skb, sizeof(*ev));
+
+		if (skb->len < ev->length || ev->length > HCI_MAX_AD_LENGTH) {
+			bt_dev_err(hdev, "Malformed advertising data");
+			break;
 		}
 
-		ptr += sizeof(*ev) + ev->length + 1;
+		skb_pull(skb, ev->length);
+
+		if (skb->len < sizeof(rssi)) {
+			bt_dev_err(hdev, "Malformed advertising rssi");
+			break;
+		}
+
+		rssi = skb->data[0];
+		skb_pull(skb, sizeof(rssi));
+
+		process_adv_report(hdev, ev->evt_type, &ev->bdaddr,
+				   ev->bdaddr_type, NULL, 0, rssi,
+				   ev->data, ev->length, false);
 	}
 
 	hci_dev_unlock(hdev);
@@ -5669,15 +5686,31 @@  static u8 ext_evt_type_to_legacy(struct hci_dev *hdev, u16 evt_type)
 static void hci_le_ext_adv_report_evt(struct hci_dev *hdev, struct sk_buff *skb)
 {
 	u8 num_reports = skb->data[0];
-	void *ptr = &skb->data[1];
 
 	hci_dev_lock(hdev);
 
+	skb_pull(skb, sizeof(num_reports));
+
 	while (num_reports--) {
-		struct hci_ev_le_ext_adv_report *ev = ptr;
+		struct hci_ev_le_ext_adv_report *ev;
 		u8 legacy_evt_type;
 		u16 evt_type;
 
+		if (skb->len < sizeof(*ev)) {
+			bt_dev_err(hdev, "Malformed ext advertising report");
+			break;
+		}
+
+		ev = (void *) skb->data;
+		skb_pull(skb, sizeof(*ev));
+
+		if (skb->len < ev->length || ev->length > HCI_MAX_AD_LENGTH) {
+			bt_dev_err(hdev, "Malformed ext advertising data");
+			break;
+		}
+
+		skb_pull(skb, ev->length);
+
 		evt_type = __le16_to_cpu(ev->evt_type);
 		legacy_evt_type = ext_evt_type_to_legacy(hdev, evt_type);
 		if (legacy_evt_type != LE_ADV_INVALID) {
@@ -5687,7 +5720,6 @@  static void hci_le_ext_adv_report_evt(struct hci_dev *hdev, struct sk_buff *skb)
 					   !(evt_type & LE_EXT_ADV_LEGACY_PDU));
 		}
 
-		ptr += sizeof(*ev) + ev->length;
 	}
 
 	hci_dev_unlock(hdev);
@@ -5873,19 +5905,26 @@  static void hci_le_direct_adv_report_evt(struct hci_dev *hdev,
 					 struct sk_buff *skb)
 {
 	u8 num_reports = skb->data[0];
-	void *ptr = &skb->data[1];
 
 	hci_dev_lock(hdev);
 
+	skb_pull(skb, sizeof(num_reports));
+
 	while (num_reports--) {
-		struct hci_ev_le_direct_adv_info *ev = ptr;
+		struct hci_ev_le_direct_adv_info *ev;
+
+		if (skb->len < sizeof(*ev)) {
+			bt_dev_err(hdev, "Malformed direct advertising");
+			break;
+		}
+
+		ev = (void *) skb->data;
+		skb_pull(skb, sizeof(*ev));
 
 		process_adv_report(hdev, ev->evt_type, &ev->bdaddr,
 				   ev->bdaddr_type, &ev->direct_addr,
 				   ev->direct_addr_type, ev->rssi, NULL, 0,
 				   false);
-
-		ptr += sizeof(*ev);
 	}
 
 	hci_dev_unlock(hdev);