mm/mmap: use find_vma_intersection() in do_mmap() for overlap

Using find_vma_intersection() avoids the need for a temporary variable and
makes the code cleaner.

Link: https://lkml.kernel.org/r/20210511014328.2902782-1-Liam.Howlett@Oracle.comSigned-off-by: NLiam R. Howlett <Liam.Howlett@Oracle.com>
Reviewed-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

mm/mmap.c

@@ -1457,9 +1457,7 @@ unsigned long do_mmap(struct file *file, unsigned long addr,
 		return addr;
 
 	if (flags & MAP_FIXED_NOREPLACE) {
-		struct vm_area_struct *vma = find_vma(mm, addr);
-
-		if (vma && vma->vm_start < addr + len)
+		if (find_vma_intersection(mm, addr, addr + len))
 			return -EEXIST;
 	}