[PATCH] drm/amdgpu: Add a GEM_CREATE mask and bugfix

[Christian König]

Am 18.02.20 um 22:46 schrieb Luben Tuikov:
> On 2020-02-17 10:08 a.m., Christian König wrote:
>> Am 17.02.20 um 15:44 schrieb Alex Deucher:
>>> On Fri, Feb 14, 2020 at 7:17 PM Luben Tuikov <luben.tuikov at amd.com> wrote:
>>>> Add a AMDGPU_GEM_CREATE_MASK and use it to check
>>>> for valid/invalid GEM create flags coming in from
>>>> userspace.
>>>>
>>>> Fix a bug in checking whether TMZ is supported at
>>>> GEM create time.
>>>>
>>>> Signed-off-by: Luben Tuikov <luben.tuikov at amd.com>
>>>> ---
>>>>    drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c | 11 ++---------
>>>>    include/uapi/drm/amdgpu_drm.h           |  2 ++
>>>>    2 files changed, 4 insertions(+), 9 deletions(-)
>>>>
>>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c
>>>> index b51a060c637d..74bb79e64fa3 100644
>>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c
>>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c
>>>> @@ -221,21 +221,14 @@ int amdgpu_gem_create_ioctl(struct drm_device *dev, void *data,
>>>>           int r;
>>>>
>>>>           /* reject invalid gem flags */
>>>> -       if (flags & ~(AMDGPU_GEM_CREATE_CPU_ACCESS_REQUIRED |
>>>> -                     AMDGPU_GEM_CREATE_NO_CPU_ACCESS |
>>>> -                     AMDGPU_GEM_CREATE_CPU_GTT_USWC |
>>>> -                     AMDGPU_GEM_CREATE_VRAM_CLEARED |
>>>> -                     AMDGPU_GEM_CREATE_VM_ALWAYS_VALID |
>>>> -                     AMDGPU_GEM_CREATE_EXPLICIT_SYNC |
>>>> -                     AMDGPU_GEM_CREATE_ENCRYPTED))
>>>> -
>>> I'd rather keep the list explicit so no one ends up forgetting to
>>> update the mask the next time new flags are added.
>> Additional to that this patch is bogus.
> So the only "additional" thing you're contributing to the review of
> this patch is calling it "bogus". Characterizing the patch with an adjective
> as "bogus" is very disturbing. What's next?

Well the patch is technical incorrect and breaks the code in a very 
subtle and hard to detect manner. Alex didn't noticed that either.

I'm not a native speaker of English, but as far as I have learned 
"bogus" is the right adjective for that.

>> We intentionally filter out the flags here which userspace is allowed to
>> specify in the GEM interface, but after this patch we would allow all
>> flags to be specified.
> I thought that that could be the case.

Then why did you send out a patch which is seriously broken like that?

I mean if I hadn't noticed it by chance we would have committed this and 
added a potentially security problematic bug to the IOCTL interface.

> But in your review why not
> recommend we have a mask to check user-settable flags? So the
> actual flags are collected and visible in one place and well
> understood that that is what is being checked and well-defined
> by a macro with an appropriate name?

See the flags tested here are the flags currently accepted by the 
amdgpu_gem_create_ioctl() function. It doesn't say anything about what 
the kernel would accept in the future.

So when we move that into the UAPI header we give userspace a 
technically incorrect value.

> Why did NO ONE comment on the bug fix below? No one.

Because you mixed up a style change into some bug fix. That people go 
for the problematic parts during code review is not really surprising at 
all.

Regards,
Christian.

>
> Regards,
> Luben
>
>> Christian.
>>
>>
>>
>>> Alex
>>>
>>>> +       if (flags & ~AMDGPU_GEM_CREATE_MASK)
>>>>                   return -EINVAL;
>>>>
>>>>           /* reject invalid gem domains */
>>>>           if (args->in.domains & ~AMDGPU_GEM_DOMAIN_MASK)
>>>>                   return -EINVAL;
>>>>
>>>> -       if (amdgpu_is_tmz(adev) && (flags & AMDGPU_GEM_CREATE_ENCRYPTED)) {
>>>> +       if (!amdgpu_is_tmz(adev) && flags & AMDGPU_GEM_CREATE_ENCRYPTED) {
>>>>                   DRM_ERROR("Cannot allocate secure buffer since TMZ is disabled\n");
>>>>                   return -EINVAL;
>>>>           }
>>>> diff --git a/include/uapi/drm/amdgpu_drm.h b/include/uapi/drm/amdgpu_drm.h
>>>> index eaf94a421901..c8463cdf4448 100644
>>>> --- a/include/uapi/drm/amdgpu_drm.h
>>>> +++ b/include/uapi/drm/amdgpu_drm.h
>>>> @@ -141,6 +141,8 @@ extern "C" {
>>>>     */
>>>>    #define AMDGPU_GEM_CREATE_ENCRYPTED            (1 << 10)
>>>>
>>>> +#define AMDGPU_GEM_CREATE_MASK                  ((1 << 11)-1)
>>>> +
>>>>    struct drm_amdgpu_gem_create_in  {
>>>>           /** the requested memory size */
>>>>           __u64 bo_size;
>>>> --
>>>> 2.25.0.232.gd8437c57fa
>>>>
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