Flipping image vertically in C

I'm trying to flip an image vertically (in C). This is what I've done so far. I think it works in theory, but when I run it I get segmentation fault. I somehow managed to fix this error a few days ago, but I didn't save it. This function that you see gives segmentation fault when I try to run. Is there a way to fix it so that it doesn't give that error and flips an image vertically?

void vertical( uint8_t array[], 
            unsigned int cols, 
            unsigned int rows )
{
   unsigned int top = 0;
   unsigned int bottom = rows-1;
   for(int r = 0; r < cols; r++)
{
   while(top != bottom && bottom > top)
    {
      int index1= r * cols + top;
      int index2= r * cols + bottom;

      int temp= array[index1];
      array[index1]= array[index2];
      array[index2] = temp;        
      bottom++;
      top++;
    } 

      top =0;
      bottom= rows-1;
 } 

}