From: Miaohe Lin <linmiaohe@xxxxxxxxxx>
Subject: mm/memory.c: fix potential pte_unmap_unlock pte error
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.
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@xxxxxxxxxx
Fixes: 42e4089c789 ("x86/speculation/l1tf: Disallow non privileged high MMIO PROT_NONE mappings")
Signed-off-by: Hongxiang Lou <louhongxiang@xxxxxxxxxx>
Signed-off-by: Miaohe Lin <linmiaohe@xxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxx>
Cc: Andi Kleen <ak@xxxxxxxxxxxxxxx>
Cc: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/memory.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
--- a/mm/memory.c~mm-fix-potential-pte_unmap_unlock-pte-error
+++ a/mm/memory.c
@@ -2177,11 +2177,11 @@ static int remap_pte_range(struct mm_str
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_str
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;
}
_
