mm: userfaultfd: fix unexpected change to src_folio when UFFDIO_MOVE fails

After ptep_clear_flush(), if we find that src_folio is pinned we will fail
UFFDIO_MOVE and put src_folio back to src_pte entry, but the change to
src_folio->{mapping,index} is not restored in this process. This is not
what we expected, so fix it.

This can cause the rmap for that page to be invalid, possibly resulting
in memory corruption.  At least swapout+migration would no longer work,
because we might fail to locate the mappings of that folio.

Link: https://lkml.kernel.org/r/[email protected]
Fixes: adef440691ba ("userfaultfd: UFFDIO_MOVE uABI")
Signed-off-by: Qi Zheng <[email protected]>
Reviewed-by: David Hildenbrand <[email protected]>
Reviewed-by: Suren Baghdasaryan <[email protected]>
Cc: Andrea Arcangeli <[email protected]>
Cc: <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

0 files changed, 0 insertions, 0 deletions