From: Hugh Dickins <firstname.lastname@example.org> To: Andrew Morton <email@example.com> Cc: "Kirill A. Shutemov" <firstname.lastname@example.org>, Andrea Arcangeli <email@example.com>, Song Liu <firstname.lastname@example.org>, email@example.com, firstname.lastname@example.org Subject: [PATCH] khugepaged: collapse_pte_mapped_thp() flush the right range Date: Sun, 2 Aug 2020 12:12:42 -0700 (PDT) [thread overview] Message-ID: <alpine.LSU.email@example.com> (raw) 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 <firstname.lastname@example.org> Cc: email@example.com # v5.4+ --- mm/khugepaged.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- 5.8-rc7/mm/khugepaged.c 2020-07-26 16:58:02.189038680 -0700 +++ linux/mm/khugepaged.c 2020-08-02 10:48:59.890925896 -0700 @@ -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));
next reply other threads:[~2020-08-02 19:13 UTC|newest] Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-08-02 19:12 Hugh Dickins [this message] 2020-08-02 19:12 ` Hugh Dickins 2020-08-02 19:15 ` [PATCH] khugepaged: collapse_pte_mapped_thp() protect the pmd lock Hugh Dickins 2020-08-02 19:15 ` Hugh Dickins 2020-08-02 21:23 ` Kirill A. Shutemov 2020-08-02 19:16 ` [PATCH] khugepaged: retract_page_tables() remember to test exit Hugh Dickins 2020-08-02 19:16 ` Hugh Dickins 2020-08-02 21:44 ` Kirill A. Shutemov 2020-08-03 0:35 ` Hugh Dickins 2020-08-03 0:35 ` Hugh Dickins 2020-08-03 8:59 ` Kirill A. Shutemov 2020-08-02 19:18 ` [PATCH] khugepaged: khugepaged_test_exit() check mmget_still_valid() Hugh Dickins 2020-08-02 19:18 ` Hugh Dickins 2020-08-14 22:13 ` [PATCH] khugepaged: adjust VM_BUG_ON_MM() in __khugepaged_enter() Hugh Dickins 2020-08-14 22:13 ` Hugh Dickins 2020-08-17 20:50 ` Yang Shi 2020-08-17 20:50 ` Yang Shi 2020-08-02 21:07 ` [PATCH] khugepaged: collapse_pte_mapped_thp() flush the right range Kirill A. Shutemov
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