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mm: provide a saner PTE walking API for modules

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commit 9fd6dad1261a541b3f5fa7dc5b152222306e6702 upstream.

Currently, the follow_pfn function is exported for modules but
follow_pte is not.  However, follow_pfn is very easy to misuse,
because it does not provide protections (so most of its callers
assume the page is writable!) and because it returns after having
already unlocked the page table lock.

Provide instead a simplified version of follow_pte that does
not have the pmdpp and range arguments.  The older version
survives as follow_invalidate_pte() for use by fs/dax.c.

Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Paolo Bonzini
2021-02-05 05:07:11 -05:00
committed by Greg Kroah-Hartman
parent 83d42c2586
commit a42150f1c9
4 changed files with 45 additions and 11 deletions
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6
include/linux/mm.h
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@@ -1655,9 +1655,11 @@ void free_pgd_range(struct mmu_gather *tlb, unsigned long addr,
unsigned long end, unsigned long floor, unsigned long ceiling);
int
copy_page_range(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma);
int follow_invalidate_pte(struct mm_struct *mm, unsigned long address,
struct mmu_notifier_range *range, pte_t **ptepp,
pmd_t **pmdpp, spinlock_t **ptlp);
int follow_pte(struct mm_struct *mm, unsigned long address,
struct mmu_notifier_range *range, pte_t **ptepp, pmd_t **pmdpp,
spinlock_t **ptlp);
pte_t **ptepp, spinlock_t **ptlp);
int follow_pfn(struct vm_area_struct *vma, unsigned long address,
unsigned long *pfn);
int follow_phys(struct vm_area_struct *vma, unsigned long address,