gpu: ion: Only map as much of the vma as the user requested

Signed-off-by: Rebecca Schultz Zavin <rebecca@android.com>
[jstultz: modified patch to apply to staging directory]
Signed-off-by: John Stultz <john.stultz@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/android/ion/ion_system_heap.c

@@ -192,6 +192,8 @@ int ion_system_heap_map_user(struct ion_heap *heap, struct ion_buffer *buffer,
 		remap_pfn_range(vma, addr, page_to_pfn(sg_page(sg)),
 				sg_dma_len(sg), vma->vm_page_prot);
 		addr += sg_dma_len(sg);
+		if (addr >= vma->vm_end)
+			return 0;
 	}
 	return 0;
 }