Messages in this thread Patch in this message | | | From | Chuhong Yuan <> | Subject | [PATCH] powerpc/mm: Use refcount_t for refcount | Date | Thu, 8 Aug 2019 15:18:08 +0800 |
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Reference counters are preferred to use refcount_t instead of atomic_t. This is because the implementation of refcount_t can prevent overflows and detect possible use-after-free. So convert atomic_t ref counters to refcount_t.
Signed-off-by: Chuhong Yuan <hslester96@gmail.com> --- arch/powerpc/mm/book3s64/mmu_context.c | 2 +- arch/powerpc/mm/book3s64/pgtable.c | 7 +++---- arch/powerpc/mm/pgtable-frag.c | 9 ++++----- include/linux/mm_types.h | 3 ++- 4 files changed, 10 insertions(+), 11 deletions(-)
diff --git a/arch/powerpc/mm/book3s64/mmu_context.c b/arch/powerpc/mm/book3s64/mmu_context.c index 2d0cb5ba9a47..f836fd5a6abc 100644 --- a/arch/powerpc/mm/book3s64/mmu_context.c +++ b/arch/powerpc/mm/book3s64/mmu_context.c @@ -231,7 +231,7 @@ static void pmd_frag_destroy(void *pmd_frag) /* drop all the pending references */ count = ((unsigned long)pmd_frag & ~PAGE_MASK) >> PMD_FRAG_SIZE_SHIFT; /* We allow PTE_FRAG_NR fragments from a PTE page */ - if (atomic_sub_and_test(PMD_FRAG_NR - count, &page->pt_frag_refcount)) { + if (refcount_sub_and_test(PMD_FRAG_NR - count, &page->pt_frag_refcount)) { pgtable_pmd_page_dtor(page); __free_page(page); } diff --git a/arch/powerpc/mm/book3s64/pgtable.c b/arch/powerpc/mm/book3s64/pgtable.c index 7d0e0d0d22c4..40056896ce4e 100644 --- a/arch/powerpc/mm/book3s64/pgtable.c +++ b/arch/powerpc/mm/book3s64/pgtable.c @@ -277,7 +277,7 @@ static pmd_t *__alloc_for_pmdcache(struct mm_struct *mm) return NULL; } - atomic_set(&page->pt_frag_refcount, 1); + refcount_set(&page->pt_frag_refcount, 1); ret = page_address(page); /* @@ -294,7 +294,7 @@ static pmd_t *__alloc_for_pmdcache(struct mm_struct *mm) * count. */ if (likely(!mm->context.pmd_frag)) { - atomic_set(&page->pt_frag_refcount, PMD_FRAG_NR); + refcount_set(&page->pt_frag_refcount, PMD_FRAG_NR); mm->context.pmd_frag = ret + PMD_FRAG_SIZE; } spin_unlock(&mm->page_table_lock); @@ -317,8 +317,7 @@ void pmd_fragment_free(unsigned long *pmd) { struct page *page = virt_to_page(pmd); - BUG_ON(atomic_read(&page->pt_frag_refcount) <= 0); - if (atomic_dec_and_test(&page->pt_frag_refcount)) { + if (refcount_dec_and_test(&page->pt_frag_refcount)) { pgtable_pmd_page_dtor(page); __free_page(page); } diff --git a/arch/powerpc/mm/pgtable-frag.c b/arch/powerpc/mm/pgtable-frag.c index a7b05214760c..4ef8231b677f 100644 --- a/arch/powerpc/mm/pgtable-frag.c +++ b/arch/powerpc/mm/pgtable-frag.c @@ -24,7 +24,7 @@ void pte_frag_destroy(void *pte_frag) /* drop all the pending references */ count = ((unsigned long)pte_frag & ~PAGE_MASK) >> PTE_FRAG_SIZE_SHIFT; /* We allow PTE_FRAG_NR fragments from a PTE page */ - if (atomic_sub_and_test(PTE_FRAG_NR - count, &page->pt_frag_refcount)) { + if (refcount_sub_and_test(PTE_FRAG_NR - count, &page->pt_frag_refcount)) { pgtable_page_dtor(page); __free_page(page); } @@ -71,7 +71,7 @@ static pte_t *__alloc_for_ptecache(struct mm_struct *mm, int kernel) return NULL; } - atomic_set(&page->pt_frag_refcount, 1); + refcount_set(&page->pt_frag_refcount, 1); ret = page_address(page); /* @@ -87,7 +87,7 @@ static pte_t *__alloc_for_ptecache(struct mm_struct *mm, int kernel) * count. */ if (likely(!pte_frag_get(&mm->context))) { - atomic_set(&page->pt_frag_refcount, PTE_FRAG_NR); + refcount_set(&page->pt_frag_refcount, PTE_FRAG_NR); pte_frag_set(&mm->context, ret + PTE_FRAG_SIZE); } spin_unlock(&mm->page_table_lock); @@ -110,8 +110,7 @@ void pte_fragment_free(unsigned long *table, int kernel) { struct page *page = virt_to_page(table); - BUG_ON(atomic_read(&page->pt_frag_refcount) <= 0); - if (atomic_dec_and_test(&page->pt_frag_refcount)) { + if (refcount_dec_and_test(&page->pt_frag_refcount)) { if (!kernel) pgtable_page_dtor(page); __free_page(page); diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h index 3a37a89eb7a7..7fe23a3faf95 100644 --- a/include/linux/mm_types.h +++ b/include/linux/mm_types.h @@ -14,6 +14,7 @@ #include <linux/uprobes.h> #include <linux/page-flags-layout.h> #include <linux/workqueue.h> +#include <linux/refcount.h> #include <asm/mmu.h> @@ -147,7 +148,7 @@ struct page { unsigned long _pt_pad_2; /* mapping */ union { struct mm_struct *pt_mm; /* x86 pgds only */ - atomic_t pt_frag_refcount; /* powerpc */ + refcount_t pt_frag_refcount; /* powerpc */ }; #if ALLOC_SPLIT_PTLOCKS spinlock_t *ptl; -- 2.20.1
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