mmap: fix remap_file_pages() regression

When using the VMA iterator, the final execution will set the variable
'next' to NULL which causes the function to fail out.  Restore the break
in the loop to exit the VMA iterator early without clearing NULL fixes the
issue.

Link: https://lore.kernel.org/lkml/29344.1666681759@jrobl/
Link: https://lkml.kernel.org/r/[email protected]
Fixes: 763ecb0 (mm: remove the vma linked list)
Signed-off-by: Liam R. Howlett <[email protected]>
Reported-by: "J. R. Okajima" <[email protected]>
Tested-by: "J. R. Okajima" <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

Author: howlett

mm/mmap.c

@@ -2852,6 +2852,9 @@ SYSCALL_DEFINE5(remap_file_pages, unsigned long, start, unsigned long, size,
 			if (next->vm_flags != vma->vm_flags)
 				goto out;
 
+			if (start + size <= next->vm_end)
+				break;
+
 			prev = next;
 		}