Display driver crashes & "unknown error" on cudaMemcpyDeviceToHost

Compiles fine, display driver crashes and I get “Cuda error in file in line : unknown error” on stdout.

Line:
CUDA_SAFE_CALL(cudaMemcpy(in, gpu_in, dataSize, cudaMemcpyDeviceToHost));

Context:
CUDA_SAFE_CALL(cudaMemcpy(gpu_in, in, dataSize , cudaMemcpyHostToDevice));

	sha1_cuda<<<grid,threads>>>(gpu_in, pat_len, mode);
	
	CUDA_SAFE_CALL(cudaMemcpy(in, gpu_in, dataSize, cudaMemcpyDeviceToHost));

“unknown error” wasn’t very descriptive and I’m not quite sure what’s going on. I’m new to using CUDA and have little idea what is going on.

If anyone has any idea, I’d appreciate your input.