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

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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/20240222080815.46291-1-zhengqi.arch@bytedance.com
Fixes: adef440691ba ("userfaultfd: UFFDIO_MOVE uABI")
Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Suren Baghdasaryan <surenb@google.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

(cherry picked from commit d7a08838ab74652f2b53fee9763f0178278c3a4b)
Conflicts:
	mm/userfaultfd.c

1. Replace folio_move_anon_rmap() with page_move_anon_rmap().

Bug: 274911254
Change-Id: Ie4bf5785244271ab233c6230ed71460fd571bd1a
Signed-off-by: Lokesh Gidra <lokeshgidra@google.com>
This commit is contained in:
Qi Zheng 2024-02-22 16:08:15 +08:00 • committed by Lokesh Gidra
parent 6ecd08eaf4
commit bfb4b24b64
1 changed files with 3 additions and 3 deletions
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6
mm/userfaultfd.c
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@ -852,9 +852,6 @@ static int move_present_pte(struct mm_struct *mm,
goto out;
}
page_move_anon_rmap(&src_folio->page, dst_vma);
WRITE_ONCE(src_folio->index, linear_page_index(dst_vma, dst_addr));
orig_src_pte = ptep_clear_flush(src_vma, src_addr, src_pte);
/* Folio got pinned from under us. Put it back and fail the move. */
if (folio_maybe_dma_pinned(src_folio)) {
@ -863,6 +860,9 @@ static int move_present_pte(struct mm_struct *mm,
goto out;
}
page_move_anon_rmap(&src_folio->page, dst_vma);
WRITE_ONCE(src_folio->index, linear_page_index(dst_vma, dst_addr));
orig_dst_pte = mk_pte(&src_folio->page, dst_vma->vm_page_prot);
/* Follow mremap() behavior and treat the entry dirty after the move */
orig_dst_pte = pte_mkwrite(pte_mkdirty(orig_dst_pte));