On Sat, Jun 13, 2026 at 8:24 PM Mario Limonciello
<[email protected]> wrote:
>
> Add a minimum-length check for the AMDGPU_CHUNK_ID_CP_GFX_SHADOW chunk in
> amdgpu_cs_pass1(), matching the gate already present for the IB, FENCE and
> BO_HANDLES chunk types.
>
> The CP_GFX_SHADOW case previously shared a bare break with the dependency
> and syncobj chunk types, which do not dereference a fixed-size struct. When
> userspace submits this chunk with length_dw == 0, vmemdup_array_user() is
> called with size 0 and returns ZERO_SIZE_PTR, which passes the IS_ERR()
> check. amdgpu_cs_p2_shadow() then dereferences chunk->kdata as a struct
> drm_amdgpu_cs_chunk_cp_gfx_shadow (reading shadow->flags), faulting on the
> ZERO_SIZE_PTR and causing a NULL-pointer dereference.
>
> This is reachable by an unprivileged process in the render group. Reject
> undersized chunks with -EINVAL during pass1 so the bad submission is
> rejected before pass2 ever dereferences the data.
>
> Signed-off-by: Mario Limonciello <[email protected]>
Fixes: ac9287055ff1 ("drm/amdgpu: add gfx shadow CS IOCTL support")
Reviewed-by: Alex Deucher <[email protected]>
> ---
> drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c | 6 +++++-
> 1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
> b/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
> index 0416827b4bb45..d63fbc7c568de 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
> @@ -248,13 +248,17 @@ static int amdgpu_cs_pass1(struct amdgpu_cs_parser *p,
> goto free_partial_kdata;
> break;
>
> + case AMDGPU_CHUNK_ID_CP_GFX_SHADOW:
> + if (size < sizeof(struct
> drm_amdgpu_cs_chunk_cp_gfx_shadow))
> + goto free_partial_kdata;
> + break;
> +
> case AMDGPU_CHUNK_ID_DEPENDENCIES:
> case AMDGPU_CHUNK_ID_SYNCOBJ_IN:
> case AMDGPU_CHUNK_ID_SYNCOBJ_OUT:
> case AMDGPU_CHUNK_ID_SCHEDULED_DEPENDENCIES:
> case AMDGPU_CHUNK_ID_SYNCOBJ_TIMELINE_WAIT:
> case AMDGPU_CHUNK_ID_SYNCOBJ_TIMELINE_SIGNAL:
> - case AMDGPU_CHUNK_ID_CP_GFX_SHADOW:
> break;
>
> default:
> --
> 2.43.0
>
