Hi,
sorry for the multiple emails but I have checked again the code and
looks like process_adv_report() reads from ev->data for a size of
ev->length.
I attach a patch that applies the bound check to both
hci_le_ext_adv_report_evt() and hci_le_adv_report_evt().
Let me know your opinion,
Best regards,
Tomas
On 3/30/19 10:20 AM, Tomas Bortoli wrote:
> Hi Dan,
>
> On 3/30/19 8:25 AM, Dan Carpenter wrote:
>> There is a potential out of bounds if "ev->length" is too high or if the
>> number of reports are too many.
>>
>> Fixes: c215e9397b00 ("Bluetooth: Process extended ADV report event")
>> Signed-off-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
> Reviewed-By: Tomas Bortoli <tomasbortoli@xxxxxxxxx>
>
>> ---
>> Not tested. I suck at pointer math, and I don't know why the protocol
>> requires a "+ 1". Please review carefully.
>>
>> net/bluetooth/hci_event.c | 3 +++
>> 1 file changed, 3 insertions(+)
>>
>> diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c
>> index 609fd6871c5a..ee945b3d12e1 100644
>> --- a/net/bluetooth/hci_event.c
>> +++ b/net/bluetooth/hci_event.c
>> @@ -5417,6 +5417,7 @@ 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];
>> + void *end = &skb->data[skb->len];
>>
>> hci_dev_lock(hdev);
>>
>> @@ -5425,6 +5426,8 @@ static void hci_le_ext_adv_report_evt(struct hci_dev *hdev, struct sk_buff *skb)
>> u8 legacy_evt_type;
>> u16 evt_type;
>>
>> + if (ptr + sizeof(*ev) + ev->length + 1 > end)
>> + break;
>
> Assuming that per each iteration, the while cycle, including the call to
> process_adv_report() read up to (sizeof(*ev) + ev->length + 1) bytes,
>
> (I don't understand why the +1, but, anyway..)
>
> If the assumption is correct, then the if condition should be:
>
> if (ptr + sizeof(*ev) + ev->length + 1 >= end)
>
> Because as soon as we try to read from the `end` pointer on, we are
> out-of-bound.. the valid skb bytes end at `end-1` (included)
>
> Note that also hci_le_adv_report_evt() is likely to need the same fix!
>
>
>> evt_type = __le16_to_cpu(ev->evt_type);
>> legacy_evt_type = ext_evt_type_to_legacy(evt_type);
>> if (legacy_evt_type != LE_ADV_INVALID) {
>>
>
>
> Kind regards,
> Tomas
>
diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c
index 609fd6871c5a..275926e0753e 100644
--- a/net/bluetooth/hci_event.c
+++ b/net/bluetooth/hci_event.c
@@ -5345,6 +5345,7 @@ 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];
+ u8 *end = &skb->data[skb->len - 1];
hci_dev_lock(hdev);
@@ -5352,6 +5353,9 @@ 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->data + ev->length > end)
+ break;
+
if (ev->length <= HCI_MAX_AD_LENGTH) {
rssi = ev->data[ev->length];
process_adv_report(hdev, ev->evt_type, &ev->bdaddr,
@@ -5417,6 +5421,7 @@ 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];
+ u8 *end = &skb->data[skb->len - 1];
hci_dev_lock(hdev);
@@ -5425,6 +5430,9 @@ static void hci_le_ext_adv_report_evt(struct hci_dev *hdev, struct sk_buff *skb)
u8 legacy_evt_type;
u16 evt_type;
+ if (ev->data + ev->length > end)
+ break;
+
evt_type = __le16_to_cpu(ev->evt_type);
legacy_evt_type = ext_evt_type_to_legacy(evt_type);
if (legacy_evt_type != LE_ADV_INVALID) {
