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

From: Kees Cook <keescook@chromium.org>
To: Suren Baghdasaryan <surenb@google.com>
Cc: Dan Carpenter <dan.carpenter@oracle.com>,
	Security Officers <security@kernel.org>,
	Kevin Deus <kdeus@google.com>,
	Samuel Ortiz <sameo@linux.intel.com>,
	"David S. Miller" <davem@davemloft.net>,
	Allen Pais <allen.pais@oracle.com>,
	linux-wireless <linux-wireless@vger.kernel.org>,
	Network Development <netdev@vger.kernel.org>,
	LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 1/1] NFC: Fix possible memory corruption when handling SHDLC I-Frame commands
Date: Tue, 14 Aug 2018 13:33:28 -0700	[thread overview]
Message-ID: <CAGXu5jKqcpbpG0Ky4-yXV4d5q10HtGwJtdyPKcrwkJUPhA_Mpg@mail.gmail.com> (raw)
In-Reply-To: <CAJuCfpHSZuabLr6+t_n7UDamJCAP6EPTNEZ6kNqWOhk2mpYADg@mail.gmail.com>

On Tue, Aug 14, 2018 at 1:26 PM, Suren Baghdasaryan <surenb@google.com> wrote:
> On Tue, Aug 14, 2018 at 9:57 AM, Suren Baghdasaryan <surenb@google.com> wrote:
>> On Tue, Aug 14, 2018 at 2:54 AM, Dan Carpenter <dan.carpenter@oracle.com> 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.

-Kees

-- 
Kees Cook
Pixel Security