From 7ece09f6cd633d195992c92f371f2809caaaceb2 Mon Sep 17 00:00:00 2001 From: Miaohe Lin Date: Wed, 24 Feb 2021 12:04:33 -0800 Subject: [PATCH] mm/memory.c: fix potential pte_unmap_unlock pte error Since commit f749ac706631 ("x86/speculation/l1tf: Disallow non privileged high MMIO PROT_NONE mappings"), when the first pfn modify is not allowed, we would break the loop with pte unchanged. Then the wrong pte - 1 would be passed to pte_unmap_unlock. Andi said: "While the fix is correct, I'm not sure if it actually is a real bug. Is there any architecture that would do something else than unlocking the underlying page? If it's just the underlying page then it should be always the same page, so no bug" Link: https://lkml.kernel.org/r/20210109080118.20885-1-linmiaohe@huawei.com Fixes: f749ac70663 ("x86/speculation/l1tf: Disallow non privileged high MMIO PROT_NONE mappings") Signed-off-by: Hongxiang Lou Signed-off-by: Miaohe Lin Cc: Thomas Gleixner Cc: Dave Hansen Cc: Andi Kleen Cc: Josh Poimboeuf Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/memory.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/mm/memory.c b/mm/memory.c index 5da964079678f..83e1bcf7a6694 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -2177,11 +2177,11 @@ static int remap_pte_range(struct mm_struct *mm, pmd_t *pmd, unsigned long addr, unsigned long end, unsigned long pfn, pgprot_t prot) { - pte_t *pte; + pte_t *pte, *mapped_pte; spinlock_t *ptl; int err = 0; - pte = pte_alloc_map_lock(mm, pmd, addr, &ptl); + mapped_pte = pte = pte_alloc_map_lock(mm, pmd, addr, &ptl); if (!pte) return -ENOMEM; arch_enter_lazy_mmu_mode(); @@ -2195,7 +2195,7 @@ static int remap_pte_range(struct mm_struct *mm, pmd_t *pmd, pfn++; } while (pte++, addr += PAGE_SIZE, addr != end); arch_leave_lazy_mmu_mode(); - pte_unmap_unlock(pte - 1, ptl); + pte_unmap_unlock(mapped_pte, ptl); return err; } -- 2.39.5