Hi Greg,
>> The function l2cap_get_conf_opt will return L2CAP_CONF_OPT_SIZE + opt->len
>> as length value. The opt->len however is in control over the remote user
>> and can be used by an attacker to gain access beyond the bounds of the
>> actual packet.
>>
>> To prevent any potential leak of heap memory, it is enough to check that
>> the resulting len calculation after calling l2cap_get_conf_opt is not
>> below zero. A well formed packet will always return >= 0 here and will
>> end with the length value being zero after the last option has been
>> parsed. In case of malformed packets messing with the opt->len field the
>> length value will become negative. If that is the case, then just abort
>> and ignore the option.
>>
>> In case an attacker uses a too short opt->len value, then garbage will
>> be parsed, but that is protected by the unknown option handling and also
>> the option parameter size checks.
>>
>> Signed-off-by: Marcel Holtmann <marcel@xxxxxxxxxxxx>
>> ---
>> net/bluetooth/l2cap_core.c | 6 ++++++
>> 1 file changed, 6 insertions(+)
>>
>> diff --git a/net/bluetooth/l2cap_core.c b/net/bluetooth/l2cap_core.c
>> index 77799e7d5a34..ccdc5c67d22a 100644
>> --- a/net/bluetooth/l2cap_core.c
>> +++ b/net/bluetooth/l2cap_core.c
>> @@ -3337,6 +3337,8 @@ static int l2cap_parse_conf_req(struct l2cap_chan *chan, void *data, size_t data
>>
>> while (len >= L2CAP_CONF_OPT_SIZE) {
>> len -= l2cap_get_conf_opt(&req, &type, &olen, &val);
>> + if (len < 0)
>> + break;
>
> <snip>
>
> Patch looks good to me, thanks for fixing this all up:
it would be still good if we can get this verified by the reporter.
Regards
Marcel
