[CUDA] Problem accessing passed kernel variable

__global__ fmultiply(float* A, float *B, float *C)
{
      int idx = blockIdx.x*blockDim.x + threadIdx.x;
      //B[idx] gives Garbage Value here..      
      C[idx] = A[idx]*B[idx];
}

int N = 10; //Array Containing Maximum of 10 elements
size_t size = N*sizeof(float);
...
cudaMalloc((**void)&a_d, size);
cudaMalloc((**void)&b_d, size);
cudaMalloc((**void)&c_d, size);

...

cudaMemcpy(a_d, a_h, size, cudaMemcpyHostToDevice);
cudaMemcpy(b_d, b_h, size, cudaMemcpyHostToDevice);

int threadsPerBlock = 256;
int noOfBlocks = (N/threadsPerBlock);

//Calling Kernel Function
fmultiply<<<threadsPerBlock, noOfBlock>>>(a_d, b_d, c_d);

cudaMemcpy(c_d, c_h, size, cudaMemcpyDeviceToHost);
......

cudaFree(a_d);
cudaFree(b_d);
cudaFree(c_d);