This is a note to let you know that I've just added the patch titled khugepaged: collapse_pte_mapped_thp() flush the right range to the 5.8-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: khugepaged-collapse_pte_mapped_thp-flush-the-right-range.patch and it can be found in the queue-5.8 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From 723a80dafed5c95889d48baab9aa433a6ffa0b4e Mon Sep 17 00:00:00 2001 From: Hugh Dickins <hughd@xxxxxxxxxx> Date: Thu, 6 Aug 2020 23:26:15 -0700 Subject: khugepaged: collapse_pte_mapped_thp() flush the right range From: Hugh Dickins <hughd@xxxxxxxxxx> commit 723a80dafed5c95889d48baab9aa433a6ffa0b4e upstream. pmdp_collapse_flush() should be given the start address at which the huge page is mapped, haddr: it was given addr, which at that point has been used as a local variable, incremented to the end address of the extent. Found by source inspection while chasing a hugepage locking bug, which I then could not explain by this. At first I thought this was very bad; then saw that all of the page translations that were not flushed would actually still point to the right pages afterwards, so harmless; then realized that I know nothing of how different architectures and models cache intermediate paging structures, so maybe it matters after all - particularly since the page table concerned is immediately freed. Much easier to fix than to think about. Fixes: 27e1f8273113 ("khugepaged: enable collapse pmd for pte-mapped THP") Signed-off-by: Hugh Dickins <hughd@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Acked-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx> Cc: Mike Kravetz <mike.kravetz@xxxxxxxxxx> Cc: Song Liu <songliubraving@xxxxxx> Cc: <stable@xxxxxxxxxxxxxxx> [5.4+] Link: http://lkml.kernel.org/r/alpine.LSU.2.11.2008021204390.27773@eggly.anvils Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- mm/khugepaged.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -1502,7 +1502,7 @@ void collapse_pte_mapped_thp(struct mm_s /* step 4: collapse pmd */ ptl = pmd_lock(vma->vm_mm, pmd); - _pmd = pmdp_collapse_flush(vma, addr, pmd); + _pmd = pmdp_collapse_flush(vma, haddr, pmd); spin_unlock(ptl); mm_dec_nr_ptes(mm); pte_free(mm, pmd_pgtable(_pmd)); Patches currently in stable-queue which might be from hughd@xxxxxxxxxx are queue-5.8/khugepaged-collapse_pte_mapped_thp-flush-the-right-range.patch queue-5.8/hugetlbfs-remove-call-to-huge_pte_alloc-without-i_mmap_rwsem.patch queue-5.8/khugepaged-khugepaged_test_exit-check-mmget_still_valid.patch queue-5.8/khugepaged-retract_page_tables-remember-to-test-exit.patch queue-5.8/khugepaged-collapse_pte_mapped_thp-protect-the-pmd-lock.patch