From 2ba99c5e08812494bc57f319fb562f527d9bacd8 Mon Sep 17 00:00:00 2001 From: Jann Horn Date: Fri, 25 Nov 2022 22:37:13 +0100 Subject: mm/khugepaged: fix GUP-fast interaction by sending IPI Since commit 70cbc3cc78a99 ("mm: gup: fix the fast GUP race against THP collapse"), the lockless_pages_from_mm() fastpath rechecks the pmd_t to ensure that the page table was not removed by khugepaged in between. However, lockless_pages_from_mm() still requires that the page table is not concurrently freed. Fix it by sending IPIs (if the architecture uses semi-RCU-style page table freeing) before freeing/reusing page tables. Link: https://lkml.kernel.org/r/20221129154730.2274278-2-jannh@google.com Link: https://lkml.kernel.org/r/20221128180252.1684965-2-jannh@google.com Link: https://lkml.kernel.org/r/20221125213714.4115729-2-jannh@google.com Fixes: ba76149f47d8 ("thp: khugepaged") Signed-off-by: Jann Horn Reviewed-by: Yang Shi Acked-by: David Hildenbrand Cc: John Hubbard Cc: Peter Xu Cc: Signed-off-by: Andrew Morton --- mm/khugepaged.c | 2 ++ 1 file changed, 2 insertions(+) (limited to 'mm/khugepaged.c') diff --git a/mm/khugepaged.c b/mm/khugepaged.c index 0a11e132ad6b..294cb75d9c22 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -1051,6 +1051,7 @@ static int collapse_huge_page(struct mm_struct *mm, unsigned long address, _pmd = pmdp_collapse_flush(vma, address, pmd); spin_unlock(pmd_ptl); mmu_notifier_invalidate_range_end(&range); + tlb_remove_table_sync_one(); spin_lock(pte_ptl); result = __collapse_huge_page_isolate(vma, address, pte, cc, @@ -1410,6 +1411,7 @@ static void collapse_and_free_pmd(struct mm_struct *mm, struct vm_area_struct *v lockdep_assert_held_write(&vma->anon_vma->root->rwsem); pmd = pmdp_collapse_flush(vma, addr, pmdp); + tlb_remove_table_sync_one(); mm_dec_nr_ptes(mm); page_table_check_pte_clear_range(mm, addr, pmd); pte_free(mm, pmd_pgtable(pmd)); -- cgit v1.2.3