[PATCH 1/2] drm/amdgpu: fix tear down order in amdgpu_vm_pt_free

[Alex Deucher]

On Fri, Dec 8, 2023 at 7:55 AM Christian König
<ckoenig.leichtzumerken at gmail.com> wrote:
>
> When freeing PD/PT with shadows it can happen that the shadow
> destruction races with detaching the PD/PT from the VM causing a NULL
> pointer dereference in the invalidation code.
>
> Fix this by detaching the the PD/PT from the VM first and then
> freeinguthe shadow instead.

typo.  Should read:
freeing the shadow.

WIth that fixed, the series is:
Reviewed-by: Alex Deucher <alexander.deucher at amd.com>


>
> Signed-off-by: Christian König <christian.koenig at amd.com>
> Fixes: https://gitlab.freedesktop.org/drm/amd/-/issues/2867
> Cc: <stable at vger.kernel.org>
> ---
>  drivers/gpu/drm/amd/amdgpu/amdgpu_vm_pt.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm_pt.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm_pt.c
> index a2287bb25223..a160265ddc07 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm_pt.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm_pt.c
> @@ -642,13 +642,14 @@ static void amdgpu_vm_pt_free(struct amdgpu_vm_bo_base *entry)
>
>         if (!entry->bo)
>                 return;
> +
> +       entry->bo->vm_bo = NULL;
>         shadow = amdgpu_bo_shadowed(entry->bo);
>         if (shadow) {
>                 ttm_bo_set_bulk_move(&shadow->tbo, NULL);
>                 amdgpu_bo_unref(&shadow);
>         }
>         ttm_bo_set_bulk_move(&entry->bo->tbo, NULL);
> -       entry->bo->vm_bo = NULL;
>
>         spin_lock(&entry->vm->status_lock);
>         list_del(&entry->vm_status);
> --
> 2.34.1
>