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From:   "Gustavo A. R. Silva" <gustavo@embeddedor.com>
To:     "Winkler, Tomas" <tomas.winkler@intel.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc:     "Usyskin, Alexander" <alexander.usyskin@intel.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "Gustavo A . R . Silva" <gustavoars@kernel.org>
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Subject: Re: [char-misc-next] Revert "mei: hdcp: Replace one-element array
 with flexible-array member"
Message-ID: <e2a00deb-831c-83a6-2580-2ec65076f7e3@embeddedor.com>
Date:   Tue, 28 Jul 2020 22:57:43 -0500
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On 7/28/20 18:16, Gustavo A. R. Silva wrote:
> 
> 
> On 7/28/20 18:04, Gustavo A. R. Silva wrote:
>> Tomas,
>>
>> Please, see some comments below...
>>
>> On 7/28/20 17:29, Winkler, Tomas wrote:
>>>>>>>
>>>>>>> Hi Tomas,
>>>>>>>
>>>>>>> On 7/28/20 16:41, Tomas Winkler wrote:
>>>>>>>> Greg please revert, this commit it changes size of struct
>>>>>>>> wired_cmd_repeater_auth_stream_req_in, this is not what firmware
>>>>>>>> is expecting.
>>>>>>>

Instead of reverting that commit, I think this patch should be applied
to fix it, if Tomas consider this is the appropiate solution:

diff --git a/drivers/misc/mei/hdcp/mei_hdcp.c b/drivers/misc/mei/hdcp/mei_hdcp.c
index d1d3e025ca0e..852374565cba 100644
--- a/drivers/misc/mei/hdcp/mei_hdcp.c
+++ b/drivers/misc/mei/hdcp/mei_hdcp.c
@@ -572,12 +572,12 @@ static int mei_hdcp_verify_mprime(struct device *dev,
               HDCP_2_2_MPRIME_LEN);
        drm_hdcp_cpu_to_be24(verify_mprime_in.seq_num_m, data->seq_num_m);
        memcpy(verify_mprime_in.streams, data->streams,
-              array_size(data->k, sizeof(*data->streams)));
+              flex_array_size(&verify_mprime_in, streams, data->k));

        verify_mprime_in.k = cpu_to_be16(data->k);

        byte = mei_cldev_send(cldev, (u8 *)&verify_mprime_in,
-                             sizeof(verify_mprime_in));
+                             struct_size(&verify_mprime_in, streams, data->k));
        if (byte < 0) {
                dev_dbg(dev, "mei_cldev_send failed. %zd\n", byte);
                return byte;

I'll write up a proper patch after getting some feedback.

Thanks
--
Gustavo

>>>>>>> Could you elaborate on what's the firmware expecting, exactly?
>>>>>> struct wired_cmd_repeater_auth_stream_req_in {
>>>>>>   -	struct hdcp2_streamid_type	streams[1];
>>>>>>   + 	struct hdcp2_streamid_type	streams[];
>>>>>> }
>>>>>>
>>>>>> But then you have, which you haven't changed to + 1 byte =
>>>>>> mei_cldev_send(cldev, (u8 *)&verify_mprime_in,
>>>>>>                               sizeof(verify_mprime_in));
>>>>>>
>>
>> I don't think the fix for this is to add 1 byte, if any, it seems
>> to be sizeof(*data->streams), or sizeof(struct hdcp2_streamid_type)
>> what needs to be added.
>>
>> But it might be better to code something like this, instead:
>>
>> diff --git a/drivers/misc/mei/hdcp/mei_hdcp.c b/drivers/misc/mei/hdcp/mei_hdcp.c
>> index e6c3dc595617..7fe63c915548 100644
>> --- a/drivers/misc/mei/hdcp/mei_hdcp.c
>> +++ b/drivers/misc/mei/hdcp/mei_hdcp.c
>> @@ -572,12 +572,12 @@ static int mei_hdcp_verify_mprime(struct device *dev,
>>                HDCP_2_2_MPRIME_LEN);
>>         drm_hdcp_cpu_to_be24(verify_mprime_in.seq_num_m, data->seq_num_m);
>>         memcpy(verify_mprime_in.streams, data->streams,
>> -              (data->k * sizeof(struct hdcp2_streamid_type)));
>> +              (data->k * sizeof(*data->streams)));
>>
>>         verify_mprime_in.k = cpu_to_be16(data->k);
>>
>>         byte = mei_cldev_send(cldev, (u8 *)&verify_mprime_in,
>> -                             sizeof(verify_mprime_in));
>> +                             struct_size(&verify_mprime_in, streams, data->k));
>>         if (byte < 0) {
>>                 dev_dbg(dev, "mei_cldev_send failed. %zd\n", byte);
>>                 return byte;
>>
>> struct_size(&verify_mprime_in, streams, data->k) will give us the size, in bytes,
>> of struct wired_cmd_repeater_auth_stream_req_in plus the size in bytes for
>> the streams[] flexible-array, which is determined by struct hdcp2_streamid_type and
>> data->k.
>>
>> What do you think?
>>
> 
> This is even better:
> 
> diff --git a/drivers/misc/mei/hdcp/mei_hdcp.c b/drivers/misc/mei/hdcp/mei_hdcp.c
> index e6c3dc595617..852374565cba 100644
> --- a/drivers/misc/mei/hdcp/mei_hdcp.c
> +++ b/drivers/misc/mei/hdcp/mei_hdcp.c
> @@ -572,12 +572,12 @@ static int mei_hdcp_verify_mprime(struct device *dev,
>                HDCP_2_2_MPRIME_LEN);
>         drm_hdcp_cpu_to_be24(verify_mprime_in.seq_num_m, data->seq_num_m);
>         memcpy(verify_mprime_in.streams, data->streams,
> -              (data->k * sizeof(struct hdcp2_streamid_type)));
> +              flex_array_size(&verify_mprime_in, streams, data->k));
> 
>         verify_mprime_in.k = cpu_to_be16(data->k);
> 
>         byte = mei_cldev_send(cldev, (u8 *)&verify_mprime_in,
> -                             sizeof(verify_mprime_in));
> +                             struct_size(&verify_mprime_in, streams, data->k));
>         if (byte < 0) {
>                 dev_dbg(dev, "mei_cldev_send failed. %zd\n", byte);
>                 return byte;
> 
> the flex_array_size() is a new helper that was designed for this situations. :)
> It calculates the size of a flexible array member within an enclosing structure,
> which is exactly the case.
> 
> Thanks
> --
> Gustavo
> 
>> See more comments below...
>>
>>>>>
>>>>> I see, this is the kind of feedback I need from people that knows the
>>>>> code better. Thanks!
>>>>>
>>>>>> But that's not the major point. Point is that we should be able to
>>>>>> review and test the code before it is merged.  You haven't run it, right?
>>>>>> There is MAINTAINERS file for a reason.
>>>>>>
>>>>>
>>>>> I'm using this command:
>>>>>
>>>>> $ scripts/get_maintainer.pl --nokeywords --nogit --nogit-fallback
>>>>>
>>>>> and this is the output for both files:
>>>>>
>>>>> $ scripts/get_maintainer.pl --nokeywords --nogit --nogit-fallback
>>>>> drivers/misc/mei/hdcp/mei_hdcp.c Arnd Bergmann <arnd@arndb.de>
>>>>> (supporter:CHAR and MISC DRIVERS) Greg Kroah-Hartman
>>>>> <gregkh@linuxfoundation.org> (supporter:CHAR and MISC DRIVERS) linux-
>>>>> kernel@vger.kernel.org (open list) $ scripts/get_maintainer.pl
>>>>> --nokeywords -- nogit --nogit-fallback
>>>>> drivers/misc/mei/hdcp/mei_hdcp.h Arnd Bergmann <arnd@arndb.de>
>>>>> (supporter:CHAR and MISC DRIVERS) Greg Kroah-Hartman
>>>>> <gregkh@linuxfoundation.org> (supporter:CHAR and MISC DRIVERS) linux-
>>>>> kernel@vger.kernel.org (open list)
>>>>
>>>>
>>>>> For some reason you don't appear on the list above. Do you see
>>>>> anything wrong with the command I'm running to get the maintainers and
>>>> lists?
>>>>
>>>> Not sure, it should be caught by drivers/misc/mei/* ?
>>>> Maybe it is not recursive? Need to check the script, frankly I usually check this
>>>> manually.
>>>>
>>>> INTEL MANAGEMENT ENGINE (mei)
>>>> M:      Tomas Winkler <tomas.winkler@intel.com>
>>>> L:      linux-kernel@vger.kernel.org
>>>> S:      Supported
>>>> F:      Documentation/driver-api/mei/*
>>>> F:      drivers/misc/mei/*
>>>> F:      drivers/watchdog/mei_wdt.c
>>>> F:      include/linux/mei_cl_bus.h
>>>> F:      include/uapi/linux/mei.h
>>>> F:      samples/mei/*
>>>>
>>>
>>> It's not recursive, when I add drivers/misc/mei/hdcp/* . It works correctly 
>>> I will post a patch.
>>>
>>
>> Great. I'm glad we got to the root cause of this issue. :)
>>
>> Thanks
>> --
>> Gustavo
>>
>>> Thanks
>>> Tomas
>>>
>>>
>>>>
>>>>>
>>>>> Thanks
>>>>> --
>>>>> Gustavo
>>>>>
>>>>>>>
>>>>>>>> I really do not appreciate that the code is bypassing driver
>>>>>>>> maintaner review, I think this is a minimum we can ask for, this
>>>>>>>> is not for a first time.
>>>>>>>>
>>>>>>>> This reverts commit c56967d674e361ebe716e66992e3c5332b25ac1f.
>>>>>>>>
>>>>>>>> Cc: Gustavo A. R. Silva <gustavoars@kernel.org>
>>>>>>>> Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
>>>>>>>> ---
>>>>>>>>  drivers/misc/mei/hdcp/mei_hdcp.c | 2 +-
>>>>>>>> drivers/misc/mei/hdcp/mei_hdcp.h | 2 +-
>>>>>>>>  2 files changed, 2 insertions(+), 2 deletions(-)
>>>>>>>>
>>>>>>>> diff --git a/drivers/misc/mei/hdcp/mei_hdcp.c
>>>>>>>> b/drivers/misc/mei/hdcp/mei_hdcp.c
>>>>>>>> index d1d3e025ca0e..e6c3dc595617 100644
>>>>>>>> --- a/drivers/misc/mei/hdcp/mei_hdcp.c
>>>>>>>> +++ b/drivers/misc/mei/hdcp/mei_hdcp.c
>>>>>>>> @@ -572,7 +572,7 @@ static int mei_hdcp_verify_mprime(struct
>>>>>>>> device
>>>>>>> *dev,
>>>>>>>>  	       HDCP_2_2_MPRIME_LEN);
>>>>>>>>  	drm_hdcp_cpu_to_be24(verify_mprime_in.seq_num_m, data-
>>>>> seq_num_m);
>>>>>>>>  	memcpy(verify_mprime_in.streams, data->streams,
>>>>>>>> -	       array_size(data->k, sizeof(*data->streams)));
>>>>>>>> +	       (data->k * sizeof(struct hdcp2_streamid_type)));
>>>>>>>>
>>>>>>>>  	verify_mprime_in.k = cpu_to_be16(data->k);
>>>>>>>>
>>>>>>>> diff --git a/drivers/misc/mei/hdcp/mei_hdcp.h
>>>>>>>> b/drivers/misc/mei/hdcp/mei_hdcp.h
>>>>>>>> index 834757f5e072..18ffc773fa18 100644
>>>>>>>> --- a/drivers/misc/mei/hdcp/mei_hdcp.h
>>>>>>>> +++ b/drivers/misc/mei/hdcp/mei_hdcp.h
>>>>>>>> @@ -358,7 +358,7 @@ struct
>>>> wired_cmd_repeater_auth_stream_req_in
>>>>> {
>>>>>>>>  	u8
>>>>>>> 	seq_num_m[HDCP_2_2_SEQ_NUM_LEN];
>>>>>>>>  	u8				m_prime[HDCP_2_2_MPRIME_LEN];
>>>>>>>>  	__be16				k;
>>>>>>>> -	struct hdcp2_streamid_type	streams[];
>>>>>>>> +	struct hdcp2_streamid_type	streams[1];
>>>>>>>>  } __packed;
>>>>>>>>
>>>>>>>>  struct wired_cmd_repeater_auth_stream_req_out {
>>>>>>>>