[PATCH] Bluetooth: stop proccessing malicious adv data

[PATCH] Bluetooth: stop proccessing malicious adv data

[Pavel Skripkin]

Syzbot reported slab-out-of-bounds read in hci_le_adv_report_evt(). The
problem was in missing validaion check.

We should check if data is not malicious and we can read next data block.
If we won't check ptr validness, code can read a way beyond skb->end and
it can cause problems, of course.

Fixes: e95beb414168 ("Bluetooth: hci_le_adv_report_evt code refactoring")
Reported-and-tested-by: syzbot+e3fcb9c4f3c2a931dc40@syzkaller.appspotmail.com
Signed-off-by: Pavel Skripkin <paskripkin@gmail.com>
---
 net/bluetooth/hci_event.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c
index 0bca035bf2dc..50d1d62c15ec 100644
--- a/net/bluetooth/hci_event.c
+++ b/net/bluetooth/hci_event.c
@@ -5780,7 +5780,8 @@ static void hci_le_adv_report_evt(struct hci_dev *hdev, struct sk_buff *skb)
 		struct hci_ev_le_advertising_info *ev = ptr;
 		s8 rssi;
 
-		if (ev->length <= HCI_MAX_AD_LENGTH) {
+		if (ev->length <= HCI_MAX_AD_LENGTH &&
+		    ev->data + ev->length <= skb_tail_pointer(skb)) {
 			rssi = ev->data[ev->length];
 			process_adv_report(hdev, ev->evt_type, &ev->bdaddr,
 					   ev->bdaddr_type, NULL, 0, rssi,
@@ -5790,6 +5791,11 @@ static void hci_le_adv_report_evt(struct hci_dev *hdev, struct sk_buff *skb)
 		}
 
 		ptr += sizeof(*ev) + ev->length + 1;
+
+		if (ptr > (void *) skb_tail_pointer(skb) - sizeof(*ev)) {
+			bt_dev_err(hdev, "Malicious advertising data. Stopping processing");
+			break;
+		}
 	}
 
 	hci_dev_unlock(hdev);
-- 
2.33.1

Re: [PATCH] Bluetooth: stop proccessing malicious adv data

[Pavel Skripkin]

On 11/1/21 10:12, Pavel Skripkin wrote:
> Syzbot reported slab-out-of-bounds read in hci_le_adv_report_evt(). The
> problem was in missing validaion check.
> 
> We should check if data is not malicious and we can read next data block.
> If we won't check ptr validness, code can read a way beyond skb->end and
> it can cause problems, of course.
> 
> Fixes: e95beb414168 ("Bluetooth: hci_le_adv_report_evt code refactoring")
> Reported-and-tested-by: syzbot+e3fcb9c4f3c2a931dc40@syzkaller.appspotmail.com
> Signed-off-by: Pavel Skripkin <paskripkin@gmail.com>
> ---

Hi, Bluetooth maintainers!

friendly ping :)


If anything is wrong with this one, please, let me know


With regards,
Pavel Skripkin


>   net/bluetooth/hci_event.c | 8 +++++++-
>   1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c
> index 0bca035bf2dc..50d1d62c15ec 100644
> --- a/net/bluetooth/hci_event.c
> +++ b/net/bluetooth/hci_event.c
> @@ -5780,7 +5780,8 @@ static void hci_le_adv_report_evt(struct hci_dev *hdev, struct sk_buff *skb)
>   		struct hci_ev_le_advertising_info *ev = ptr;
>   		s8 rssi;
>   
> -		if (ev->length <= HCI_MAX_AD_LENGTH) {
> +		if (ev->length <= HCI_MAX_AD_LENGTH &&
> +		    ev->data + ev->length <= skb_tail_pointer(skb)) {
>   			rssi = ev->data[ev->length];
>   			process_adv_report(hdev, ev->evt_type, &ev->bdaddr,
>   					   ev->bdaddr_type, NULL, 0, rssi,
> @@ -5790,6 +5791,11 @@ static void hci_le_adv_report_evt(struct hci_dev *hdev, struct sk_buff *skb)
>   		}
>   
>   		ptr += sizeof(*ev) + ev->length + 1;
> +
> +		if (ptr > (void *) skb_tail_pointer(skb) - sizeof(*ev)) {
> +			bt_dev_err(hdev, "Malicious advertising data. Stopping processing");
> +			break;
> +		}
>   	}
>   
>   	hci_dev_unlock(hdev);
> 

Re: [PATCH] Bluetooth: stop proccessing malicious adv data

[Marcel Holtmann]

Hi Pavel,

> Syzbot reported slab-out-of-bounds read in hci_le_adv_report_evt(). The
> problem was in missing validaion check.
> 
> We should check if data is not malicious and we can read next data block.
> If we won't check ptr validness, code can read a way beyond skb->end and
> it can cause problems, of course.
> 
> Fixes: e95beb414168 ("Bluetooth: hci_le_adv_report_evt code refactoring")
> Reported-and-tested-by: syzbot+e3fcb9c4f3c2a931dc40@syzkaller.appspotmail.com
> Signed-off-by: Pavel Skripkin <paskripkin@gmail.com>
> ---
> net/bluetooth/hci_event.c | 8 +++++++-
> 1 file changed, 7 insertions(+), 1 deletion(-)

patch has been applied to bluetooth-next tree.

Regards

Marcel