From: Miaohe Lin <linmiaohe@xxxxxxxxxx> Subject: mm/memory.c: fix potential pte_unmap_unlock pte error If all pte entry is none in 'non-create' case, we would break the loop with pte unchanged. Then the wrong pte - 1 would be passed to pte_unmap_unlock. This is a theoretical issue which may not be a real bug. So it's not worth cc stable. Link: https://lkml.kernel.org/r/20210205081925.59809-1-linmiaohe@xxxxxxxxxx Fixes: aee16b3cee27 ("Add apply_to_page_range() which applies a function to a pte range") Signed-off-by: Miaohe Lin <linmiaohe@xxxxxxxxxx> Reviewed-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Cc: Ingo Molnar <mingo@xxxxxxx> Cc: Ian Pratt <ian.pratt@xxxxxxxxxxxxx> Cc: Chris Wright <chrisw@xxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/memory.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) --- a/mm/memory.c~mm-memoryc-fix-potential-pte_unmap_unlock-pte-error +++ a/mm/memory.c @@ -2394,18 +2394,18 @@ static int apply_to_pte_range(struct mm_ pte_fn_t fn, void *data, bool create, pgtbl_mod_mask *mask) { - pte_t *pte; + pte_t *pte, *mapped_pte; int err = 0; spinlock_t *ptl; if (create) { - pte = (mm == &init_mm) ? + mapped_pte = pte = (mm == &init_mm) ? pte_alloc_kernel_track(pmd, addr, mask) : pte_alloc_map_lock(mm, pmd, addr, &ptl); if (!pte) return -ENOMEM; } else { - pte = (mm == &init_mm) ? + mapped_pte = pte = (mm == &init_mm) ? pte_offset_kernel(pmd, addr) : pte_offset_map_lock(mm, pmd, addr, &ptl); } @@ -2428,7 +2428,7 @@ static int apply_to_pte_range(struct mm_ arch_leave_lazy_mmu_mode(); if (mm != &init_mm) - pte_unmap_unlock(pte-1, ptl); + pte_unmap_unlock(mapped_pte, ptl); return err; } _
