Re: [PATCH v3 1/2] Bluetooth: Fix not checking advertisement bondaries

[Salvatore Bonaccorso <carnil@debian.org>]

Hi Luiz,

On Fri, Oct 23, 2020 at 05:22:50PM -0700, Luiz Augusto von Dentz 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>
> ---
>  net/bluetooth/hci_event.c | 73 ++++++++++++++++++++++++++++++---------
>  1 file changed, 56 insertions(+), 17 deletions(-)
> 
> 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);
> -- 
> 2.26.2

Are both these two patches in the series still something which needs
to be applied as fixes, or has it been solved in other ways?

If so can you shorten the Fixes tags to the first 12 characters of the
SHA-1 ID, cf.
https://www.kernel.org/doc/html/latest/process/submitting-patches.html
.

Regards,
Salvatore