Re: [PATCH 0/9] drm: Annotate structs with __counted_by

[Christian König]

Am 02.10.23 um 18:53 schrieb Kees Cook:
> On Mon, Oct 02, 2023 at 11:06:19AM -0400, Alex Deucher wrote:
> > On Mon, Oct 2, 2023 at 5:20 AM Christian König
> > <ckoenig.leichtzumerken@xxxxxxxxx> wrote:
> > > Am 29.09.23 um 21:33 schrieb Kees Cook:
> > > > On Fri, 22 Sep 2023 10:32:05 -0700, Kees Cook wrote:
> > > > > This is a batch of patches touching drm for preparing for the coming
> > > > > implementation by GCC and Clang of the __counted_by attribute. Flexible
> > > > > array members annotated with __counted_by can have their accesses
> > > > > bounds-checked at run-time checking via CONFIG_UBSAN_BOUNDS (for array
> > > > > indexing) and CONFIG_FORTIFY_SOURCE (for strcpy/memcpy-family functions).
> > > > >
> > > > > As found with Coccinelle[1], add __counted_by to structs that would
> > > > > benefit from the annotation.
> > > > >
> > > > > [...]
> > > > Since this got Acks, I figure I should carry it in my tree. Let me know
> > > > if this should go via drm instead.
> > > >
> > > > Applied to for-next/hardening, thanks!
> > > >
> > > > [1/9] drm/amd/pm: Annotate struct smu10_voltage_dependency_table with __counted_by
> > > >         https://git.kernel.org/kees/c/a6046ac659d6
> > > STOP! In a follow up discussion Alex and I figured out that this won't work.
> I'm so confused; from the discussion I saw that Alex said both instances
> were false positives?
>
> > > The value in the structure is byte swapped based on some firmware
> > > endianness which not necessary matches the CPU endianness.
> > SMU10 is APU only so the endianess of the SMU firmware and the CPU
> > will always match.
> Which I think is what is being said here?
>
> > > Please revert that one from going upstream if it's already on it's way.
> > >
> > > And because of those reasons I strongly think that patches like this
> > > should go through the DRM tree :)
> Sure, that's fine -- please let me know. It was others Acked/etc. Who
> should carry these patches?

Probably best if the relevant maintainer pick them up individually.

Some of those structures are filled in by firmware/hardware and only the 
maintainers can judge if that value actually matches what the compiler 
needs.

We have cases where individual bits are used as flags or when the size 
is byte swapped etc...

Even Alex and I didn't immediately say how and where that field is 
actually used and had to dig that up. That's where the confusion came from.

Regards,
Christian.

> Thanks!
>
> -Kees
>
>
> > > Regards,
> > > Christian.
> > >
> > > > [2/9] drm/amdgpu/discovery: Annotate struct ip_hw_instance with __counted_by
> > > >         https://git.kernel.org/kees/c/4df33089b46f
> > > > [3/9] drm/i915/selftests: Annotate struct perf_series with __counted_by
> > > >         https://git.kernel.org/kees/c/ffd3f823bdf6
> > > > [4/9] drm/msm/dpu: Annotate struct dpu_hw_intr with __counted_by
> > > >         https://git.kernel.org/kees/c/2de35a989b76
> > > > [5/9] drm/nouveau/pm: Annotate struct nvkm_perfdom with __counted_by
> > > >         https://git.kernel.org/kees/c/188aeb08bfaa
> > > > [6/9] drm/vc4: Annotate struct vc4_perfmon with __counted_by
> > > >         https://git.kernel.org/kees/c/59a54dc896c3
> > > > [7/9] drm/virtio: Annotate struct virtio_gpu_object_array with __counted_by
> > > >         https://git.kernel.org/kees/c/5cd476de33af
> > > > [8/9] drm/vmwgfx: Annotate struct vmw_surface_dirty with __counted_by
> > > >         https://git.kernel.org/kees/c/b426f2e5356a
> > > > [9/9] drm/v3d: Annotate struct v3d_perfmon with __counted_by
> > > >         https://git.kernel.org/kees/c/dc662fa1b0e4
> > > >
> > > > Take care,