Re: [PATCH v7 1/6] drm/amdgpu: Fix init ordering in amdgpu_vram_mgr_init()

[Christian König]

Arun please take a look at this.

Thanks,
Christian.

On 7/3/26 15:05, Thomas Hellström wrote:
> drmm_cgroup_register_region() is called before INIT_LIST_HEAD() and
> gpu_buddy_init() in amdgpu_vram_mgr_init(). If it fails, the function
> returns early and bypasses those initializations.
> 
> Since adev->mman.initialized is set to true before amdgpu_vram_mgr_init()
> is called, a failure triggers amdgpu_ttm_fini(), which calls
> amdgpu_vram_mgr_fini(), which then:
> 
>  - Calls list_for_each_entry_safe() on reservations_pending and
>    reserved_pages, whose list_head::next pointers are zero-initialized
>    (NULL). The loop does not recognize them as empty and dereferences NULL.
> 
>  - Calls gpu_buddy_fini(), which iterates free_trees[] unconditionally
>    via for_each_free_tree(). Since mm->free_trees is NULL
>    (never allocated), this dereferences NULL.
> 
> Both result in a kernel panic on the module load error path.
> 
> Fix by moving drmm_cgroup_register_region() to after the list and buddy
> allocator are fully initialized, so the teardown path is safe to run.
> 
> Reported-by: Sashiko-bot <sashiko-bot@xxxxxxxxxx>
> Closes: https://sashiko.dev/#/patchset/20260428073116.15687-1-thomas.hellstrom@xxxxxxxxxxxxxxx?part=4
> Fixes: 2b624a2c1865 ("drm/ttm: Handle cgroup based eviction in TTM")
> Cc: Friedrich Vock <friedrich.vock@xxxxxx>
> Cc: Maarten Lankhorst <dev@xxxxxxxxxxxx>
> Cc: Tejun Heo <tj@xxxxxxxxxx>
> Cc: Maxime Ripard <mripard@xxxxxxxxxx>
> Cc: Christian König <christian.koenig@xxxxxxx>
> Cc: Alex Deucher <alexander.deucher@xxxxxxx>
> Cc: amd-gfx@xxxxxxxxxxxxxxxxxxxxx
> Cc: dri-devel@xxxxxxxxxxxxxxxxxxxxx
> Cc: <stable@xxxxxxxxxxxxxxx> # v6.14+
> Assisted-by: GitHub_Copilot:claude-sonnet-4.6
> Signed-off-by: Thomas Hellström <thomas.hellstrom@xxxxxxxxxxxxxxx>
> ---
>  drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c
> index 2a241a5b12c4..ac3f71d77140 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c
> @@ -918,9 +918,6 @@ int amdgpu_vram_mgr_init(struct amdgpu_device *adev)
>  	struct ttm_resource_manager *man = &mgr->manager;
>  	int err;
>  
> -	man->cg = drmm_cgroup_register_region(adev_to_drm(adev), "vram", adev->gmc.real_vram_size);
> -	if (IS_ERR(man->cg))
> -		return PTR_ERR(man->cg);
>  	ttm_resource_manager_init(man, &adev->mman.bdev,
>  				  adev->gmc.real_vram_size);
>  
> @@ -935,6 +932,10 @@ int amdgpu_vram_mgr_init(struct amdgpu_device *adev)
>  	if (err)
>  		return err;
>  
> +	man->cg = drmm_cgroup_register_region(adev_to_drm(adev), "vram", adev->gmc.real_vram_size);
> +	if (IS_ERR(man->cg))
> +		return PTR_ERR(man->cg);
> +
>  	ttm_set_driver_manager(&adev->mman.bdev, TTM_PL_VRAM, &mgr->manager);
>  	ttm_resource_manager_set_used(man, true);
>  	return 0;