d3d11va_device_create() crashes when the graphics device is disabled.

[haviet]

Summary of the bug:
1) Environment:
Purpose: Decoding video via HW Acceleration

Before the crash: It decodes video well via both CUDA, DXVA2 and D3D11VA.
Crash condition: Disables the graphics device.
Graphics device: NVIDIA
OS: Windows 10 x64 Pro
Version:
ffmpeg version N-90264-g80798e3857 Copyright (c) 2000-2018 the FFmpeg developers

built with Microsoft (R) C/C++ Optimizing Compiler Version 19.13.26128 for x64
configuration: --toolchain=msvc --arch=x86_64 --target-os=win64

libavutil 56. 8.100 / 56. 8.100
libavcodec 58. 14.100 / 58. 14.100
libavformat 58. 10.100 / 58. 10.100
libavdevice 58. 2.100 / 58. 2.100

2) How to reproduce:

In Windows 10 OS, go to the menu as below and disable the graphics device
Computer Manager -> Device Manager -> Display adapters -> Graphics device.

Then make a call to the function

av_hwdevice_ctx_create(&pHwDeviceCtx, AV_HWDEVICE_TYPE_D3D11VA, "hw", nullptr, 0);

This shall trigger the crash in d3d11va_device_create() function.
The order of calls leading to the crash is:
-> av_hwdevice_ctx_create
-> d3d11va_device_create
-> ID3D11Device_QueryInterface

Note that I had tried other device types as below, though the function return an error but it did not cause crash.

AV_HWDEVICE_TYPE_CUDA, <-- OK
AV_HWDEVICE_TYPE_DXVA2, <-- OK
AV_HWDEVICE_TYPE_QSV, <-- OK
AV_HWDEVICE_TYPE_OPENCL, <-- OK
AV_HWDEVICE_TYPE_D3D11VA, <-- crashed

//	function is crashed
static int d3d11va_device_create(AVHWDeviceContext *ctx, const char *device,
                                 AVDictionary *opts, int flags)
{
    AVD3D11VADeviceContext *device_hwctx = ctx->hwctx;

    //	other lines ...

    hr = mD3D11CreateDevice(pAdapter, pAdapter ? D3D_DRIVER_TYPE_UNKNOWN : D3D_DRIVER_TYPE_HARDWARE, NULL, creationFlags, NULL, 0,
                   D3D11_SDK_VERSION, &device_hwctx->device, NULL, NULL);

//	Right here the hr status is:
	hr = 0x887a0004 : The specified device interface or feature level is not supported on this system. 
	
	// The block "if (FAILED(hr))" should be placed here.

    if (pAdapter) {
        DXGI_ADAPTER_DESC2 desc;
        hr = IDXGIAdapter2_GetDesc(pAdapter, &desc);
        if (!FAILED(hr)) {
            av_log(ctx, AV_LOG_INFO, "Using device %04x:%04x (%ls).\n",
                   desc.VendorId, desc.DeviceId, desc.Description);
        }
        IDXGIAdapter_Release(pAdapter);
    }
    if (FAILED(hr)) {
        av_log(ctx, AV_LOG_ERROR, "Failed to create Direct3D device (%lx)\n", (long)hr);
        return AVERROR_UNKNOWN;
    }

	//	Crashed here due to device_hwctx->device is NULL
	//
    hr = ID3D11Device_QueryInterface(device_hwctx->device, &IID_ID3D10Multithread, (void **)&pMultithread);
    if (SUCCEEDED(hr)) {
        ID3D10Multithread_SetMultithreadProtected(pMultithread, TRUE);
        ID3D10Multithread_Release(pMultithread);
    }
}

I realized that the call to mD3D11CreateDevice() returns
hr = 0x887a0004 : "The specified device interface or feature level is not supported on this system."
But hr value is not checked before moving to the next statement.
That is the cause.

[jkqxz]

Fixed in 44000b7744a0a3c425bc6d8d924b4efa866aad39.

Thank you for the report!