userfaultfd: change src_folio after ensuring it's unpinned in UFFDIO_MOVE

Commit d7a08838ab74 ("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: adef440691ba ("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>

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 9859aa4f755380a88013c70791e6e6df90ce861f..89f58c7603b255feb3dceaccfee603a503c40e49 100644 (file)
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -2259,9 +2259,6 @@ 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)) {
@@ -2270,6 +2267,9 @@ 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);