Date:   Wed, 9 Oct 2019 20:46:45 +0000
From:   "Lakha, Bhawanpreet" <Bhawanpreet.Lakha@....com>
To:     Daniel Vetter <daniel@...ll.ch>
CC:     Colin Ian King <colin.king@...onical.com>,
        "Wentland, Harry" <Harry.Wentland@....com>,
        "Li, Sun peng (Leo)" <Sunpeng.Li@....com>,
        "Deucher, Alexander" <Alexander.Deucher@....com>,
        "Koenig, Christian" <Christian.Koenig@....com>,
        "Zhou, David(ChunMing)" <David1.Zhou@....com>,
        David Airlie <airlied@...ux.ie>,
        amd-gfx mailing list <amd-gfx@...ts.freedesktop.org>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: drm/amd/display: Add HDCP module - static analysis bug report

I misunderstood and was talking about the ksv validation specifically 
(usage of drm_hdcp_check_ksvs_revoked()).

For the defines I will create patches to use drm_hdcp where it is usable.


Bhawan

On 2019-10-09 2:43 p.m., Daniel Vetter wrote:
> On Wed, Oct 9, 2019 at 8:23 PM Lakha, Bhawanpreet
> <Bhawanpreet.Lakha@....com> wrote:
>> Hi,
>>
>> The reason we don't use drm_hdcp is because our policy is to do hdcp
>> verification using PSP/HW (onboard secure processor).
> i915 also uses hw to auth, we still use the parts from drm_hdcp ...
> Did you actually look at what's in there? It's essentially just shared
> defines and data structures from the standard, plus a few minimal
> helpers to en/decode some bits. Just from a quick read the entire
> patch very much looks like midlayer everywhere design that we
> discussed back when DC landed ...
> -Daniel
>
>> Bhawan
>>
>> On 2019-10-09 12:32 p.m., Daniel Vetter wrote:
>>> On Thu, Oct 03, 2019 at 11:08:03PM +0100, Colin Ian King wrote:
>>>> Hi,
>>>>
>>>> Static analysis with Coverity has detected a potential issue with
>>>> function validate_bksv in
>>>> drivers/gpu/drm/amd/display/modules/hdcp/hdcp1_execution.c with recent
>>>> commit:
>>>>
>>>> commit ed9d8e2bcb003ec94658cafe9b1bb3960e2139ec
>>>> Author: Bhawanpreet Lakha <Bhawanpreet.Lakha@....com>
>>>> Date:   Tue Aug 6 17:52:01 2019 -0400
>>>>
>>>>       drm/amd/display: Add HDCP module
>>> I think the real question here is ... why is this not using drm_hdcp?
>>> -Daniel
>>>
>>>> The analysis is as follows:
>>>>
>>>>    28 static inline enum mod_hdcp_status validate_bksv(struct mod_hdcp *hdcp)
>>>>    29 {
>>>>
>>>> CID 89852 (#1 of 1): Out-of-bounds read (OVERRUN)
>>>>
>>>> 1. overrun-local:
>>>> Overrunning array of 5 bytes at byte offset 7 by dereferencing pointer
>>>> (uint64_t *)hdcp->auth.msg.hdcp1.bksv.
>>>>
>>>>    30        uint64_t n = *(uint64_t *)hdcp->auth.msg.hdcp1.bksv;
>>>>    31        uint8_t count = 0;
>>>>    32
>>>>    33        while (n) {
>>>>    34                count++;
>>>>    35                n &= (n - 1);
>>>>    36        }
>>>>
>>>> hdcp->auth.msg.hdcp1.bksv is an array of 5 uint8_t as defined in
>>>> drivers/gpu/drm/amd/display/modules/hdcp/hdcp.h as follows:
>>>>
>>>> struct mod_hdcp_message_hdcp1 {
>>>>           uint8_t         an[8];
>>>>           uint8_t         aksv[5];
>>>>           uint8_t         ainfo;
>>>>           uint8_t         bksv[5];
>>>>           uint16_t        r0p;
>>>>           uint8_t         bcaps;
>>>>           uint16_t        bstatus;
>>>>           uint8_t         ksvlist[635];
>>>>           uint16_t        ksvlist_size;
>>>>           uint8_t         vp[20];
>>>>
>>>>           uint16_t        binfo_dp;
>>>> };
>>>>
>>>> variable n is going to contain the contains of r0p and bcaps. I'm not
>>>> sure if that is intentional. If not, then the count is going to be
>>>> incorrect if these are non-zero.
>>>>
>>>> Colin
>> _______________________________________________
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>
>

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