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

[Arunpravin Paneer Selvam <arunpravin.paneerselvam@amd.com>]

On 7/3/2026 6:38 PM, Christian König wrote:
> Arun please take a look at this.
Sure Christian. This fix looks correct to me.
Reviewed-by: Arunpravin Paneer Selvam <Arunpravin.PaneerSelvam@amd.com>

Thanks,
Arun.
>
> 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@kernel.org>
>> Closes: https://sashiko.dev/#/patchset/20260428073116.15687-1-thomas.hellstrom@linux.intel.com?part=4
>> Fixes: 2b624a2c1865 ("drm/ttm: Handle cgroup based eviction in TTM")
>> Cc: Friedrich Vock <friedrich.vock@gmx.de>
>> Cc: Maarten Lankhorst <dev@lankhorst.se>
>> Cc: Tejun Heo <tj@kernel.org>
>> Cc: Maxime Ripard <mripard@kernel.org>
>> Cc: Christian König <christian.koenig@amd.com>
>> Cc: Alex Deucher <alexander.deucher@amd.com>
>> Cc: amd-gfx@lists.freedesktop.org
>> Cc: dri-devel@lists.freedesktop.org
>> Cc: <stable@vger.kernel.org> # v6.14+
>> Assisted-by: GitHub_Copilot:claude-sonnet-4.6
>> Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
>> ---
>>   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;