Commit e9c74b54 authored by Qi Zheng's avatar Qi Zheng Committed by Andrew Morton
Browse files

mm: userfaultfd: move_pages_pte() use pte_offset_map_rw_nolock() 

In move_pages_pte(), we may modify the dst_pte and src_pte after acquiring
the ptl, so convert it to using pte_offset_map_rw_nolock().  But since we
will use pte_same() to detect the change of the pte entry, there is no
need to get pmdval, so just pass a dummy variable to it.

Link: https://lkml.kernel.org/r/1530e8fdbfc72eacf3b095babe139ce3d715600a.1727332572.git.zhengqi.arch@bytedance.com


Signed-off-by: default avatarQi Zheng <zhengqi.arch@bytedance.com>
Reviewed-by: default avatarMuchun Song <muchun.song@linux.dev>
Cc: David Hildenbrand <david@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Mike Rapoport (Microsoft) <rppt@kernel.org>
Cc: Peter Xu <peterx@redhat.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Vishal Moola (Oracle) <vishal.moola@gmail.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 04965da7

mm/userfaultfd.c

+12 −3
Original line number Diff line number Diff line
@@ -1135,7 +1135,7 @@ static int move_pages_pte(struct mm_struct *mm, pmd_t *dst_pmd, pmd_t *src_pmd, 
	spinlock_t *src_ptl, *dst_ptl;

	pte_t *src_pte = NULL;

	pte_t *dst_pte = NULL;



	pmd_t dummy_pmdval;

	struct folio *src_folio = NULL;

	struct anon_vma *src_anon_vma = NULL;

	struct mmu_notifier_range range;
@@ -1146,7 +1146,14 @@ static int move_pages_pte(struct mm_struct *mm, pmd_t *dst_pmd, pmd_t *src_pmd, 
				src_addr, src_addr + PAGE_SIZE);

	mmu_notifier_invalidate_range_start(&range);

retry:

	dst_pte = pte_offset_map_nolock(mm, dst_pmd, dst_addr, &dst_ptl);

	/*

	 * Use the maywrite version to indicate that dst_pte will be modified,

	 * but since we will use pte_same() to detect the change of the pte

	 * entry, there is no need to get pmdval, so just pass a dummy variable

	 * to it.

	 */

	dst_pte = pte_offset_map_rw_nolock(mm, dst_pmd, dst_addr, &dummy_pmdval,

					   &dst_ptl);



	/* Retry if a huge pmd materialized from under us */

	if (unlikely(!dst_pte)) {
@@ -1154,7 +1161,9 @@ static int move_pages_pte(struct mm_struct *mm, pmd_t *dst_pmd, pmd_t *src_pmd, 
		goto out;

	}



	src_pte = pte_offset_map_nolock(mm, src_pmd, src_addr, &src_ptl);

	/* same as dst_pte */

	src_pte = pte_offset_map_rw_nolock(mm, src_pmd, src_addr, &dummy_pmdval,

					   &src_ptl);



	/*

	 * We held the mmap_lock for reading so MADV_DONTNEED