[PATCH] drm/amdkfd: fix kgd_mem memory leak when importing dmabuf

[Felix Kuehling]

Am 2022-07-26 um 07:15 schrieb Lang Yu:
> The kgd_mem memory allocated in amdgpu_amdkfd_gpuvm_import_dmabuf()
> is not freed properly.
>
> Explicitly free it in amdgpu_amdkfd_gpuvm_free_memory_of_gpu()
> under condition "mem->bo->kfd_bo != mem".
>
> Suggested-by: Felix Kuehling <Felix.Kuehling at amd.com>
> Signed-off-by: Lang Yu <Lang.Yu at amd.com>

Some suggestions inline to make the code more readable. Other than that, 
the patch is

Reviewed-by: Felix Kuehling <Felix.Kuehling at amd.com>


> ---
>   drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c | 8 ++++++++
>   1 file changed, 8 insertions(+)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c
> index 6bba6961eee7..086bed40cf34 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c
> @@ -1803,6 +1803,7 @@ int amdgpu_amdkfd_gpuvm_free_memory_of_gpu(
>   		uint64_t *size)
>   {
>   	struct amdkfd_process_info *process_info = mem->process_info;
> +	struct kgd_mem *tmp_mem = mem->bo->kfd_bo;

Right, you need this because using mem after drm_gem_object_put would be 
a potential use-after-free. Instead of saving this pointer with some 
obscure variable name, you could just save a bool with a more meaningful 
name. E.g.:

	bool use_release_notifier = (mem->bo->kfd_bo == mem);

This way you have the entire condition in one place, and the variable 
name explains the meaning.


>   	unsigned long bo_size = mem->bo->tbo.base.size;
>   	struct kfd_mem_attachment *entry, *tmp;
>   	struct bo_vm_reservation_context ctx;
> @@ -1895,6 +1896,13 @@ int amdgpu_amdkfd_gpuvm_free_memory_of_gpu(
>   	 */
>   	drm_gem_object_put(&mem->bo->tbo.base);
>   
> +	/*
> +	 * For kgd_mem allocated in amdgpu_amdkfd_gpuvm_import_dmabuf(),
> +	 * explicitly free it here.
> +	 */
> +	if (mem != tmp_mem)

	if (!use_release_notifier)
		kfree(mem);

Regards,
   Felix


> +		kfree(mem);
> +
>   	return ret;
>   }
>