[bug report] dma-buf: heaps: Add heap helpers

[Dan Carpenter]

Hello John Stultz,

The patch 7b87ea704fd9: "dma-buf: heaps: Add heap helpers" from Oct
21, 2019, leads to the following static checker warning:

	drivers/dma-buf/heaps/heap-helpers.c:165 dma_heap_vm_fault()
	warn: uncapped user index 'buffer->pages[vmf->pgoff]'

drivers/dma-buf/heaps/heap-helpers.c
   160  static vm_fault_t dma_heap_vm_fault(struct vm_fault *vmf)
   161  {
   162          struct vm_area_struct *vma = vmf->vma;
   163          struct heap_helper_buffer *buffer = vma->vm_private_data;
   164  
   165          vmf->page = buffer->pages[vmf->pgoff];
                                          ^^^^^^^^^^
Smatch for some reason thinks this needs to be checked.  Smatch also
gets confused by these fault handlers and thinks there is some recursion
involved...

   166          get_page(vmf->page);
   167  
   168          return 0;
   169  }
   170  
   171  static const struct vm_operations_struct dma_heap_vm_ops = {
   172          .fault = dma_heap_vm_fault,
   173  };
   174  

regards,
dan carpenter