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.
>
> The "reporter" seems to have disappeared once they reported this stuff,
> so I would not count on them doing anything here, we asked numerous
> times :(
>
> If the patches look correct, I recommend just merging it and I can
> backport it to the stable releases and the distros can pick it up from
> there.
I think that I have Johan merge them into bluetooth-next first and let them sit a little so we can verify they do not break anything else. You can pick them up later into -stable if nobody complained and we didn’t break qualification.
Regards
Marcel
