userfaultfd: change src_folio after ensuring it's unpinned in UFFDIO_…

…MOVE

commit c0205ea upstream.

Commit d7a0883 ("mm: userfaultfd: fix unexpected change to src_folio
when UFFDIO_MOVE fails") moved the src_folio->{mapping, index} changing to
after clearing the page-table and ensuring that it's not pinned.  This
avoids failure of swapout+migration and possibly memory corruption.

However, the commit missed fixing it in the huge-page case.

Link: https://lkml.kernel.org/r/20240404171726.2302435-1-lokeshgidra@google.com
Fixes: adef440 ("userfaultfd: UFFDIO_MOVE uABI")
Signed-off-by: Lokesh Gidra <lokeshgidra@google.com>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Kalesh Singh <kaleshsingh@google.com>
Cc: Lokesh Gidra <lokeshgidra@google.com>
Cc: Nicolas Geoffray <ngeoffray@google.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Qi Zheng <zhengqi.arch@bytedance.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Lokesh Gidra <lokeshgidra@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

mm/huge_memory.c

@@ -2244,9 +2244,6 @@ int move_pages_huge_pmd(struct mm_struct *mm, pmd_t *dst_pmd, pmd_t *src_pmd, pm
 		goto unlock_ptls;
 	}
 
-	folio_move_anon_rmap(src_folio, dst_vma);
-	WRITE_ONCE(src_folio->index, linear_page_index(dst_vma, dst_addr));
-
 	src_pmdval = pmdp_huge_clear_flush(src_vma, src_addr, src_pmd);
 	/* Folio got pinned from under us. Put it back and fail the move. */
 	if (folio_maybe_dma_pinned(src_folio)) {
@@ -2255,6 +2252,9 @@ int move_pages_huge_pmd(struct mm_struct *mm, pmd_t *dst_pmd, pmd_t *src_pmd, pm
 		goto unlock_ptls;
 	}
 
+	folio_move_anon_rmap(src_folio, dst_vma);
+	WRITE_ONCE(src_folio->index, linear_page_index(dst_vma, dst_addr));
+
 	_dst_pmd = mk_huge_pmd(&src_folio->page, dst_vma->vm_page_prot);
 	/* Follow mremap() behavior and treat the entry dirty after the move */
 	_dst_pmd = pmd_mkwrite(pmd_mkdirty(_dst_pmd), dst_vma);