[PATCH] drm/amdgpu: Handle null atom context in VBIOS info ioctl

[Alex Deucher]

On Tue, Sep 5, 2023 at 12:15 PM Francis, David <David.Francis at amd.com> wrote:
>
> [AMD Official Use Only - General]
>
>
> [AMD Official Use Only - General]
>
> Yeah we've had JIRAs (e.g. https://ontrack-internal.amd.com/browse/SWDEV-409711 ) raised that ASAN can't compile the thunk due to using = {0} . Using memset is definitely preferred to save trouble later.
>
>  Kent
>
> This is kernel code, not thunk. {} and {0} are extensively used throughout
> the kernel in general and our driver in particular, so I don't see this causing problems.

Speaking for the kernel, we've seen problematic behavior when using {}
vs {0} vs memset.  memset always seems to do the right thing, the
others don't.  E.g., there was a series of patch sets to switch
everything from {} to {0} or vice versa, we just traded one issue for
another.  For this patch, you can probably just drop that hunk as I
don't see a need to change it.  Whether you switch to memset or not is
up to you.

Alex


>
>  David
>
> -----Original Message-----
> From: amd-gfx <amd-gfx-bounces at lists.freedesktop.org> On Behalf Of Alex
> Deucher
> Sent: Tuesday, September 5, 2023 10:53 AM
> To: Francis, David <David.Francis at amd.com>
> Cc: amd-gfx at lists.freedesktop.org
> Subject: Re: [PATCH] drm/amdgpu: Handle null atom context in VBIOS info ioctl
>
> On Tue, Sep 5, 2023 at 10:50 AM David Francis <David.Francis at amd.com> wrote:
>
> On some APU systems, there is no atom context and so the
> atom_context struct is null.
>
> Add a check to the VBIOS_INFO branch of amdgpu_info_ioctl
> to handle this case, returning all zeroes.
>
> Signed-off-by: David Francis <David.Francis at amd.com>
> ---
>  drivers/gpu/drm/amd/amdgpu/amdgpu_kms.c | 19 ++++++++++++-------
>  1 file changed, 12 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_kms.c
>
> b/drivers/gpu/drm/amd/amdgpu/amdgpu_kms.c
>
> index 3a48bec10aea..86748290ead7 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_kms.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_kms.c
> @@ -947,16 +947,21 @@ int amdgpu_info_ioctl(struct drm_device *dev, void
>
> *data, struct drm_file *filp)
>
>                                         ? -EFAULT : 0;
>                 }
>                 case AMDGPU_INFO_VBIOS_INFO: {
> -                       struct drm_amdgpu_info_vbios vbios_info = {};
> +                       struct drm_amdgpu_info_vbios vbios_info = {0};
>
> IIRC, these should be equivalent.  That said, I believe memset is
> generally preferred as not all compilers seem to handle these cases
> correctly.
>
> Alex
>
>                         struct atom_context *atom_context;
>
>                         atom_context = adev->mode_info.atom_context;
> -                       memcpy(vbios_info.name, atom_context->name,
>
> sizeof(atom_context->name));
>
> -                       memcpy(vbios_info.vbios_pn, atom_context->vbios_pn,
>
> sizeof(atom_context->vbios_pn));
>
> -                       vbios_info.version = atom_context->version;
> -                       memcpy(vbios_info.vbios_ver_str, atom_context->vbios_ver_str,
> -                                               sizeof(atom_context->vbios_ver_str));
> -                       memcpy(vbios_info.date, atom_context->date,
>
> sizeof(atom_context->date));
>
> +                       if (atom_context) {
> +                               memcpy(vbios_info.name, atom_context->name,
> +                                      sizeof(atom_context->name));
> +                               memcpy(vbios_info.vbios_pn, atom_context->vbios_pn,
> +                                      sizeof(atom_context->vbios_pn));
> +                               vbios_info.version = atom_context->version;
> +                               memcpy(vbios_info.vbios_ver_str, atom_context-
> vbios_ver_str,
> +                                      sizeof(atom_context->vbios_ver_str));
> +                               memcpy(vbios_info.date, atom_context->date,
> +                                      sizeof(atom_context->date));
> +                       }
>
>                         return copy_to_user(out, &vbios_info,
>                                                 min((size_t)size, sizeof(vbios_info))) ? -EFAULT : 0;
> --
> 2.34.1
>