[PATCH 2/3] powerpc/mm/book3s/64: Add proper pte access check helper
From: Aneesh Kumar K.V <hidden>
Date: 2017-12-04 02:19:30
Subsystem:
linux for powerpc (32-bit and 64-bit), the rest · Maintainers:
Madhavan Srinivasan, Linus Torvalds
pte_access_premitted get called in get_user_pages_fast path. If we have marked the pte PROT_NONE, we should not allow a read access on the address. With the current implementation we are not checking the READ and only check for WRITE. This is needed on archs like ppc64 that implement PROT_NONE using RWX access instead of _PAGE_PRESENT. Also add pte_user check just to make sure we are not accessing kernel mapping. Signed-off-by: Aneesh Kumar K.V <redacted> --- arch/powerpc/include/asm/book3s/64/pgtable.h | 41 ++++++++++++++++++++++++++++ 1 file changed, 41 insertions(+)
diff --git a/arch/powerpc/include/asm/book3s/64/pgtable.h b/arch/powerpc/include/asm/book3s/64/pgtable.h
index 2006fec40a00..efa5bd6bc1d3 100644
--- a/arch/powerpc/include/asm/book3s/64/pgtable.h
+++ b/arch/powerpc/include/asm/book3s/64/pgtable.h@@ -520,6 +520,30 @@ static inline int pte_present(pte_t pte) { return !!(pte_raw(pte) & cpu_to_be64(_PAGE_PRESENT)); } + +#define pte_access_permitted pte_access_permitted +static inline bool pte_access_permitted(pte_t pte, bool write) +{ + unsigned long pteval = pte_val(pte); + /* Also check for pte_user */ + unsigned long clear_pte_bits = _PAGE_PRIVILEGED; + /* + * _PAGE_READ is needed for any access and will be + * cleared for PROT_NONE + */ + unsigned long need_pte_bits = _PAGE_PRESENT | _PAGE_READ; + + if (write) + need_pte_bits |= _PAGE_WRITE; + + if ((pteval & need_pte_bits) != need_pte_bits) + return false; + + if ((pteval & clear_pte_bits) == clear_pte_bits) + return false; + return true; +} + /* * Conversion functions: convert a page and protection to a page entry, * and a page entry and page directory to the page they refer to.
@@ -824,6 +848,11 @@ static inline int pud_bad(pud_t pud) return hash__pud_bad(pud); } +#define pud_access_permitted pud_access_permitted +static inline bool pud_access_permitted(pud_t pud, bool write) +{ + return pte_access_permitted(pud_pte(pud), write); +} #define pgd_write(pgd) pte_write(pgd_pte(pgd)) static inline void pgd_set(pgd_t *pgdp, unsigned long val)
@@ -863,6 +892,12 @@ static inline int pgd_bad(pgd_t pgd) return hash__pgd_bad(pgd); } +#define pgd_access_permitted pgd_access_permitted +static inline bool pgd_access_permitted(pgd_t pgd, bool write) +{ + return pte_access_permitted(pgd_pte(pgd), write); +} + extern struct page *pgd_page(pgd_t pgd); /* Pointers in the page table tree are physical addresses */
@@ -984,6 +1019,12 @@ static inline int pmd_protnone(pmd_t pmd) #define __pmd_write(pmd) __pte_write(pmd_pte(pmd)) #define pmd_savedwrite(pmd) pte_savedwrite(pmd_pte(pmd)) +#define pmd_access_permitted pmd_access_permitted +static inline bool pmd_access_permitted(pmd_t pmd, bool write) +{ + return pte_access_permitted(pmd_pte(pmd), write); +} + #ifdef CONFIG_TRANSPARENT_HUGEPAGE extern pmd_t pfn_pmd(unsigned long pfn, pgprot_t pgprot); extern pmd_t mk_pmd(struct page *page, pgprot_t pgprot);
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2.14.3