From: Peter Xu <peterx@xxxxxxxxxx> Subject: mm: clear vmf->pte after pte_unmap_same() returns pte_unmap_same() will always unmap the pte pointer. After the unmap, vmf->pte will not be valid any more, we should clear it. It was safe only because no one is accessing vmf->pte after pte_unmap_same() returns, since the only caller of pte_unmap_same() (so far) is do_swap_page(), where vmf->pte will in most cases be overwritten very soon. Directly pass in vmf into pte_unmap_same() and then we can also avoid the long parameter list too, which should be a nice cleanup. Link: https://lkml.kernel.org/r/20210915181533.11188-1-peterx@xxxxxxxxxx Signed-off-by: Peter Xu <peterx@xxxxxxxxxx> Reviewed-by: Miaohe Lin <linmiaohe@xxxxxxxxxx> Reviewed-by: David Hildenbrand <david@xxxxxxxxxx> Reviewed-by: Liam Howlett <liam.howlett@xxxxxxxxxx> Acked-by: Hugh Dickins <hughd@xxxxxxxxxx> Cc: Alistair Popple <apopple@xxxxxxxxxx> Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx> Cc: Axel Rasmussen <axelrasmussen@xxxxxxxxxx> Cc: Jerome Glisse <jglisse@xxxxxxxxxx> Cc: "Kirill A . Shutemov" <kirill@xxxxxxxxxxxxx> Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx> Cc: Mike Rapoport <rppt@xxxxxxxxxxxxxxxxxx> Cc: Yang Shi <shy828301@xxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/memory.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) --- a/mm/memory.c~mm-clear-vmf-pte-after-pte_unmap_same-returns +++ a/mm/memory.c @@ -2728,19 +2728,19 @@ EXPORT_SYMBOL_GPL(apply_to_existing_page * proceeding (but do_wp_page is only called after already making such a check; * and do_anonymous_page can safely check later on). */ -static inline int pte_unmap_same(struct mm_struct *mm, pmd_t *pmd, - pte_t *page_table, pte_t orig_pte) +static inline int pte_unmap_same(struct vm_fault *vmf) { int same = 1; #if defined(CONFIG_SMP) || defined(CONFIG_PREEMPTION) if (sizeof(pte_t) > sizeof(unsigned long)) { - spinlock_t *ptl = pte_lockptr(mm, pmd); + spinlock_t *ptl = pte_lockptr(vmf->vma->vm_mm, vmf->pmd); spin_lock(ptl); - same = pte_same(*page_table, orig_pte); + same = pte_same(*vmf->pte, vmf->orig_pte); spin_unlock(ptl); } #endif - pte_unmap(page_table); + pte_unmap(vmf->pte); + vmf->pte = NULL; return same; } @@ -3492,7 +3492,7 @@ vm_fault_t do_swap_page(struct vm_fault vm_fault_t ret = 0; void *shadow = NULL; - if (!pte_unmap_same(vma->vm_mm, vmf->pmd, vmf->pte, vmf->orig_pte)) + if (!pte_unmap_same(vmf)) goto out; entry = pte_to_swp_entry(vmf->orig_pte); _
