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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>
References: <20200728214139.3129532-1-tomas.winkler@intel.com>
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From:   "Gustavo A. R. Silva" <gustavo@embeddedor.com>
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Subject: Re: [char-misc-next] Revert "mei: hdcp: Replace one-element array
 with flexible-array member"
Message-ID: <c4a93287-6010-8ea4-cab2-09efa49e3391@embeddedor.com>
Date:   Tue, 28 Jul 2020 18:04:20 -0500
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Sender: linux-kernel-owner@vger.kernel.org
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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.
>>>>>
>>>>> 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?

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 {
>>>>>>