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Subject[PATCH] mm/memory.c: fix potential pte_unmap_unlock pte error
Date
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.

Fixes: aee16b3cee27 ("Add apply_to_page_range() which applies a function to a pte range")
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
---
mm/memory.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/mm/memory.c b/mm/memory.c
index 9d68a2340589..b2d6a0a6088b 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2394,18 +2394,18 @@ static int apply_to_pte_range(struct mm_struct *mm, pmd_t *pmd,
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_struct *mm, pmd_t *pmd,
arch_leave_lazy_mmu_mode();

if (mm != &init_mm)
- pte_unmap_unlock(pte-1, ptl);
+ pte_unmap_unlock(mapped_pte, ptl);
return err;
}

--
2.19.1
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