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mm/memory.c: fix potential pte_unmap_unlock pte error

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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@huawei.com
Fixes: aee16b3cee27 ("Add apply_to_page_range() which applies a function to a pte range")
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Ian Pratt <ian.pratt@xensource.com>
Cc: Chris Wright <chrisw@sous-sol.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Miaohe Lin 2021-02-24 12:04:42 -08:00 committed by Linus Torvalds
parent 374437a274
commit 8abb50c76b
1 changed files with 4 additions and 4 deletions
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8
mm/memory.c
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@ -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, pte_fn_t fn, void *data, bool create,
pgtbl_mod_mask *mask) pgtbl_mod_mask *mask)
{ {
pte_t *pte; pte_t *pte, *mapped_pte;
int err = 0; int err = 0;
spinlock_t *ptl; spinlock_t *ptl;
if (create) { if (create) {
pte = (mm == &init_mm) ? mapped_pte = pte = (mm == &init_mm) ?
pte_alloc_kernel_track(pmd, addr, mask) : pte_alloc_kernel_track(pmd, addr, mask) :
pte_alloc_map_lock(mm, pmd, addr, &ptl); pte_alloc_map_lock(mm, pmd, addr, &ptl);
if (!pte) if (!pte)
return -ENOMEM; return -ENOMEM;
} else { } else {
pte = (mm == &init_mm) ? mapped_pte = pte = (mm == &init_mm) ?
pte_offset_kernel(pmd, addr) : pte_offset_kernel(pmd, addr) :
pte_offset_map_lock(mm, pmd, addr, &ptl); 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(); arch_leave_lazy_mmu_mode();
if (mm != &init_mm) if (mm != &init_mm)
pte_unmap_unlock(pte-1, ptl); pte_unmap_unlock(mapped_pte, ptl);
return err; return err;
} }