From: Dave Hansen <[email protected]> init_mm is for kernel-exclusive use. If someone is allocating page tables for it, do not set _PAGE_USER on them.
Signed-off-by: Dave Hansen <[email protected]> Reviewed-by: Thomas Gleixner <[email protected]> Cc: Moritz Lipp <[email protected]> Cc: Daniel Gruss <[email protected]> Cc: Michael Schwarz <[email protected]> Cc: Richard Fellner <[email protected]> Cc: Andy Lutomirski <[email protected]> Cc: Linus Torvalds <[email protected]> Cc: Kees Cook <[email protected]> Cc: Hugh Dickins <[email protected]> Cc: [email protected] --- b/arch/x86/include/asm/pgalloc.h | 33 ++++++++++++++++++++++++++++----- 1 file changed, 28 insertions(+), 5 deletions(-) diff -puN arch/x86/include/asm/pgalloc.h~kaiser-prep-clear-_PAGE_USER-for-init_mm arch/x86/include/asm/pgalloc.h --- a/arch/x86/include/asm/pgalloc.h~kaiser-prep-clear-_PAGE_USER-for-init_mm 2017-11-08 10:45:25.928681403 -0800 +++ b/arch/x86/include/asm/pgalloc.h 2017-11-08 10:45:25.931681403 -0800 @@ -61,20 +61,37 @@ static inline void __pte_free_tlb(struct ___pte_free_tlb(tlb, pte); } +/* + * init_mm is for kernel-exclusive use. Any page tables that + * are seteup for it should not be usable by userspace. + * + * This also *signals* to code (like KAISER) that this page table + * entry is for kernel-exclusive use. + */ +static inline pteval_t mm_pgtable_flags(struct mm_struct *mm) +{ + if (!mm || (mm == &init_mm)) + return _KERNPG_TABLE; + return _PAGE_TABLE; +} + static inline void pmd_populate_kernel(struct mm_struct *mm, pmd_t *pmd, pte_t *pte) { + pteval_t pgtable_flags = mm_pgtable_flags(mm); + paravirt_alloc_pte(mm, __pa(pte) >> PAGE_SHIFT); - set_pmd(pmd, __pmd(__pa(pte) | _PAGE_TABLE)); + set_pmd(pmd, __pmd(__pa(pte) | pgtable_flags)); } static inline void pmd_populate(struct mm_struct *mm, pmd_t *pmd, struct page *pte) { + pteval_t pgtable_flags = mm_pgtable_flags(mm); unsigned long pfn = page_to_pfn(pte); paravirt_alloc_pte(mm, pfn); - set_pmd(pmd, __pmd(((pteval_t)pfn << PAGE_SHIFT) | _PAGE_TABLE)); + set_pmd(pmd, __pmd(((pteval_t)pfn << PAGE_SHIFT) | pgtable_flags)); } #define pmd_pgtable(pmd) pmd_page(pmd) @@ -117,16 +134,20 @@ extern void pud_populate(struct mm_struc #else /* !CONFIG_X86_PAE */ static inline void pud_populate(struct mm_struct *mm, pud_t *pud, pmd_t *pmd) { + pteval_t pgtable_flags = mm_pgtable_flags(mm); + paravirt_alloc_pmd(mm, __pa(pmd) >> PAGE_SHIFT); - set_pud(pud, __pud(_PAGE_TABLE | __pa(pmd))); + set_pud(pud, __pud(__pa(pmd) | pgtable_flags)); } #endif /* CONFIG_X86_PAE */ #if CONFIG_PGTABLE_LEVELS > 3 static inline void p4d_populate(struct mm_struct *mm, p4d_t *p4d, pud_t *pud) { + pteval_t pgtable_flags = mm_pgtable_flags(mm); + paravirt_alloc_pud(mm, __pa(pud) >> PAGE_SHIFT); - set_p4d(p4d, __p4d(_PAGE_TABLE | __pa(pud))); + set_p4d(p4d, __p4d(__pa(pud) | pgtable_flags)); } static inline pud_t *pud_alloc_one(struct mm_struct *mm, unsigned long addr) @@ -155,8 +176,10 @@ static inline void __pud_free_tlb(struct #if CONFIG_PGTABLE_LEVELS > 4 static inline void pgd_populate(struct mm_struct *mm, pgd_t *pgd, p4d_t *p4d) { + pteval_t pgtable_flags = mm_pgtable_flags(mm); + paravirt_alloc_p4d(mm, __pa(p4d) >> PAGE_SHIFT); - set_pgd(pgd, __pgd(_PAGE_TABLE | __pa(p4d))); + set_pgd(pgd, __pgd(__pa(p4d) | pgtable_flags)); } static inline p4d_t *p4d_alloc_one(struct mm_struct *mm, unsigned long addr) _
