[PATCH] mm: Fix potential pte_unmap_unlock pte error

[Miaohe Lin]

Since commit 42e4089c7890 ("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.

Fixes: 42e4089c789 ("x86/speculation/l1tf: Disallow non privileged high MMIO 
PROT_NONE mappings")
Signed-off-by: Hongxiang Lou <louhongxi...@huawei.com>
Signed-off-by: Miaohe Lin <linmia...@huawei.com>
Cc: sta...@kernel.org
---
 mm/memory.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/mm/memory.c b/mm/memory.c
index feff48e1465a..351b78ebd5a4 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2165,11 +2165,11 @@ 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();
@@ -2183,7 +2183,7 @@ 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;
 }
 
-- 
2.19.1