Re: [PATCH 1/1] NFC: Fix possible memory corruption when handling SHDLC I-Frame commands

[Kees Cook]

On Tue, Aug 14, 2018 at 1:55 PM, Suren Baghdasaryan <surenb@xxxxxxxxxx> wrote:
> On Tue, Aug 14, 2018 at 1:33 PM, Kees Cook <keescook@xxxxxxxxxxxx> wrote:
>> On Tue, Aug 14, 2018 at 1:26 PM, Suren Baghdasaryan <surenb@xxxxxxxxxx> wrote:
>>> On Tue, Aug 14, 2018 at 9:57 AM, Suren Baghdasaryan <surenb@xxxxxxxxxx> wrote:
>>>> On Tue, Aug 14, 2018 at 2:54 AM, Dan Carpenter <dan.carpenter@xxxxxxxxxx> wrote:
>>>>> Thanks.  This is great.  I'm so glad these are finally getting fixed.
>>>>>
>>>>> Do we need to fix nfc_hci_msg_rx_work() and nfc_hci_recv_from_llc() as
>>>>> well?  In nfc_hci_recv_from_llc() we allow pipe to be NFC_HCI_FRAGMENT
>>>>> (0x7f) so that's one element beyond the end of the array and the
>>>>> NFC_HCI_HCP_RESPONSE isn't checked.
>>>>>
>>>>> Also nci_hci_msg_rx_work() and nci_hci_data_received_cb() use
>>>>> NCI_HCP_MSG_GET_PIPE() so those could be off by one.
>>>>
>>>> Good point. From hci.h:
>>>>
>>>> /*
>>>>  * According to specification 102 622 chapter 4.4 Pipes,
>>>>  * the pipe identifier is 7 bits long.
>>>>  */
>>>> #define NFC_HCI_MAX_PIPES 127
>>>>
>>>> And then:
>>>>
>>>> struct nfc_hci_dev {
>>>>   ...
>>>>   struct nfc_hci_pipe pipes[NFC_HCI_MAX_PIPES];
>>>>   ...
>>>> }
>>>>
>>>> I think the correct fix would be to change it to:
>>>>
>>>>   struct nfc_hci_pipe pipes[NFC_HCI_MAX_PIPES + 1];
>>>>
>>>> What do you think?
>>>>
>>>
>>> Just to be clear, this would fix the problem Dan described in his
>>> reply and it should be implemented in a separate patch. The original
>>> fix is still valid.
>>
>> I think you could merge the fixes into a single patch.
>
> Couple reasons I would prefer to keep them separate:
> - I feel that descriptions for these two issues should be different
> and it's easier if we don't mix them up
> - This one is already merged into Android kernels, so would be easier
> to introduce the second fix separately
> - I would like to give credit to people who noticed the problem (in
> this case those are different people)
>
> However if more people think we should fix both issues in the same
> patch I'll happily do that.
> Thanks!

If it's already landed separately somewhere else, then yeah, 2 patches
sounds good. No objection either way from me!

-Kees

-- 
Kees Cook
Pixel Security