From 57f0f512b273f60d52568b8c6b77e17f5636edc0 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Andr=C3=A9=20Fabian=20Silva=20Delgado?= Date: Wed, 5 Aug 2015 17:04:01 -0300 Subject: Initial import --- mm/mprotect.c | 433 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 433 insertions(+) create mode 100644 mm/mprotect.c (limited to 'mm/mprotect.c') diff --git a/mm/mprotect.c b/mm/mprotect.c new file mode 100644 index 000000000..88584838e --- /dev/null +++ b/mm/mprotect.c @@ -0,0 +1,433 @@ +/* + * mm/mprotect.c + * + * (C) Copyright 1994 Linus Torvalds + * (C) Copyright 2002 Christoph Hellwig + * + * Address space accounting code + * (C) Copyright 2002 Red Hat Inc, All Rights Reserved + */ + +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +/* + * For a prot_numa update we only hold mmap_sem for read so there is a + * potential race with faulting where a pmd was temporarily none. This + * function checks for a transhuge pmd under the appropriate lock. It + * returns a pte if it was successfully locked or NULL if it raced with + * a transhuge insertion. + */ +static pte_t *lock_pte_protection(struct vm_area_struct *vma, pmd_t *pmd, + unsigned long addr, int prot_numa, spinlock_t **ptl) +{ + pte_t *pte; + spinlock_t *pmdl; + + /* !prot_numa is protected by mmap_sem held for write */ + if (!prot_numa) + return pte_offset_map_lock(vma->vm_mm, pmd, addr, ptl); + + pmdl = pmd_lock(vma->vm_mm, pmd); + if (unlikely(pmd_trans_huge(*pmd) || pmd_none(*pmd))) { + spin_unlock(pmdl); + return NULL; + } + + pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, ptl); + spin_unlock(pmdl); + return pte; +} + +static unsigned long change_pte_range(struct vm_area_struct *vma, pmd_t *pmd, + unsigned long addr, unsigned long end, pgprot_t newprot, + int dirty_accountable, int prot_numa) +{ + struct mm_struct *mm = vma->vm_mm; + pte_t *pte, oldpte; + spinlock_t *ptl; + unsigned long pages = 0; + + pte = lock_pte_protection(vma, pmd, addr, prot_numa, &ptl); + if (!pte) + return 0; + + arch_enter_lazy_mmu_mode(); + do { + oldpte = *pte; + if (pte_present(oldpte)) { + pte_t ptent; + bool preserve_write = prot_numa && pte_write(oldpte); + + /* + * Avoid trapping faults against the zero or KSM + * pages. See similar comment in change_huge_pmd. + */ + if (prot_numa) { + struct page *page; + + page = vm_normal_page(vma, addr, oldpte); + if (!page || PageKsm(page)) + continue; + + /* Avoid TLB flush if possible */ + if (pte_protnone(oldpte)) + continue; + } + + ptent = ptep_modify_prot_start(mm, addr, pte); + ptent = pte_modify(ptent, newprot); + if (preserve_write) + ptent = pte_mkwrite(ptent); + + /* Avoid taking write faults for known dirty pages */ + if (dirty_accountable && pte_dirty(ptent) && + (pte_soft_dirty(ptent) || + !(vma->vm_flags & VM_SOFTDIRTY))) { + ptent = pte_mkwrite(ptent); + } + ptep_modify_prot_commit(mm, addr, pte, ptent); + pages++; + } else if (IS_ENABLED(CONFIG_MIGRATION)) { + swp_entry_t entry = pte_to_swp_entry(oldpte); + + if (is_write_migration_entry(entry)) { + pte_t newpte; + /* + * A protection check is difficult so + * just be safe and disable write + */ + make_migration_entry_read(&entry); + newpte = swp_entry_to_pte(entry); + if (pte_swp_soft_dirty(oldpte)) + newpte = pte_swp_mksoft_dirty(newpte); + set_pte_at(mm, addr, pte, newpte); + + pages++; + } + } + } while (pte++, addr += PAGE_SIZE, addr != end); + arch_leave_lazy_mmu_mode(); + pte_unmap_unlock(pte - 1, ptl); + + return pages; +} + +static inline unsigned long change_pmd_range(struct vm_area_struct *vma, + pud_t *pud, unsigned long addr, unsigned long end, + pgprot_t newprot, int dirty_accountable, int prot_numa) +{ + pmd_t *pmd; + struct mm_struct *mm = vma->vm_mm; + unsigned long next; + unsigned long pages = 0; + unsigned long nr_huge_updates = 0; + unsigned long mni_start = 0; + + pmd = pmd_offset(pud, addr); + do { + unsigned long this_pages; + + next = pmd_addr_end(addr, end); + if (!pmd_trans_huge(*pmd) && pmd_none_or_clear_bad(pmd)) + continue; + + /* invoke the mmu notifier if the pmd is populated */ + if (!mni_start) { + mni_start = addr; + mmu_notifier_invalidate_range_start(mm, mni_start, end); + } + + if (pmd_trans_huge(*pmd)) { + if (next - addr != HPAGE_PMD_SIZE) + split_huge_page_pmd(vma, addr, pmd); + else { + int nr_ptes = change_huge_pmd(vma, pmd, addr, + newprot, prot_numa); + + if (nr_ptes) { + if (nr_ptes == HPAGE_PMD_NR) { + pages += HPAGE_PMD_NR; + nr_huge_updates++; + } + + /* huge pmd was handled */ + continue; + } + } + /* fall through, the trans huge pmd just split */ + } + this_pages = change_pte_range(vma, pmd, addr, next, newprot, + dirty_accountable, prot_numa); + pages += this_pages; + } while (pmd++, addr = next, addr != end); + + if (mni_start) + mmu_notifier_invalidate_range_end(mm, mni_start, end); + + if (nr_huge_updates) + count_vm_numa_events(NUMA_HUGE_PTE_UPDATES, nr_huge_updates); + return pages; +} + +static inline unsigned long change_pud_range(struct vm_area_struct *vma, + pgd_t *pgd, unsigned long addr, unsigned long end, + pgprot_t newprot, int dirty_accountable, int prot_numa) +{ + pud_t *pud; + unsigned long next; + unsigned long pages = 0; + + pud = pud_offset(pgd, addr); + do { + next = pud_addr_end(addr, end); + if (pud_none_or_clear_bad(pud)) + continue; + pages += change_pmd_range(vma, pud, addr, next, newprot, + dirty_accountable, prot_numa); + } while (pud++, addr = next, addr != end); + + return pages; +} + +static unsigned long change_protection_range(struct vm_area_struct *vma, + unsigned long addr, unsigned long end, pgprot_t newprot, + int dirty_accountable, int prot_numa) +{ + struct mm_struct *mm = vma->vm_mm; + pgd_t *pgd; + unsigned long next; + unsigned long start = addr; + unsigned long pages = 0; + + BUG_ON(addr >= end); + pgd = pgd_offset(mm, addr); + flush_cache_range(vma, addr, end); + set_tlb_flush_pending(mm); + do { + next = pgd_addr_end(addr, end); + if (pgd_none_or_clear_bad(pgd)) + continue; + pages += change_pud_range(vma, pgd, addr, next, newprot, + dirty_accountable, prot_numa); + } while (pgd++, addr = next, addr != end); + + /* Only flush the TLB if we actually modified any entries: */ + if (pages) + flush_tlb_range(vma, start, end); + clear_tlb_flush_pending(mm); + + return pages; +} + +unsigned long change_protection(struct vm_area_struct *vma, unsigned long start, + unsigned long end, pgprot_t newprot, + int dirty_accountable, int prot_numa) +{ + unsigned long pages; + + if (is_vm_hugetlb_page(vma)) + pages = hugetlb_change_protection(vma, start, end, newprot); + else + pages = change_protection_range(vma, start, end, newprot, dirty_accountable, prot_numa); + + return pages; +} + +int +mprotect_fixup(struct vm_area_struct *vma, struct vm_area_struct **pprev, + unsigned long start, unsigned long end, unsigned long newflags) +{ + struct mm_struct *mm = vma->vm_mm; + unsigned long oldflags = vma->vm_flags; + long nrpages = (end - start) >> PAGE_SHIFT; + unsigned long charged = 0; + pgoff_t pgoff; + int error; + int dirty_accountable = 0; + + if (newflags == oldflags) { + *pprev = vma; + return 0; + } + + /* + * If we make a private mapping writable we increase our commit; + * but (without finer accounting) cannot reduce our commit if we + * make it unwritable again. hugetlb mapping were accounted for + * even if read-only so there is no need to account for them here + */ + if (newflags & VM_WRITE) { + if (!(oldflags & (VM_ACCOUNT|VM_WRITE|VM_HUGETLB| + VM_SHARED|VM_NORESERVE))) { + charged = nrpages; + if (security_vm_enough_memory_mm(mm, charged)) + return -ENOMEM; + newflags |= VM_ACCOUNT; + } + } + + /* + * First try to merge with previous and/or next vma. + */ + pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT); + *pprev = vma_merge(mm, *pprev, start, end, newflags, + vma->anon_vma, vma->vm_file, pgoff, vma_policy(vma)); + if (*pprev) { + vma = *pprev; + goto success; + } + + *pprev = vma; + + if (start != vma->vm_start) { + error = split_vma(mm, vma, start, 1); + if (error) + goto fail; + } + + if (end != vma->vm_end) { + error = split_vma(mm, vma, end, 0); + if (error) + goto fail; + } + +success: + /* + * vm_flags and vm_page_prot are protected by the mmap_sem + * held in write mode. + */ + vma->vm_flags = newflags; + dirty_accountable = vma_wants_writenotify(vma); + vma_set_page_prot(vma); + + change_protection(vma, start, end, vma->vm_page_prot, + dirty_accountable, 0); + + vm_stat_account(mm, oldflags, vma->vm_file, -nrpages); + vm_stat_account(mm, newflags, vma->vm_file, nrpages); + perf_event_mmap(vma); + return 0; + +fail: + vm_unacct_memory(charged); + return error; +} + +SYSCALL_DEFINE3(mprotect, unsigned long, start, size_t, len, + unsigned long, prot) +{ + unsigned long vm_flags, nstart, end, tmp, reqprot; + struct vm_area_struct *vma, *prev; + int error = -EINVAL; + const int grows = prot & (PROT_GROWSDOWN|PROT_GROWSUP); + prot &= ~(PROT_GROWSDOWN|PROT_GROWSUP); + if (grows == (PROT_GROWSDOWN|PROT_GROWSUP)) /* can't be both */ + return -EINVAL; + + if (start & ~PAGE_MASK) + return -EINVAL; + if (!len) + return 0; + len = PAGE_ALIGN(len); + end = start + len; + if (end <= start) + return -ENOMEM; + if (!arch_validate_prot(prot)) + return -EINVAL; + + reqprot = prot; + /* + * Does the application expect PROT_READ to imply PROT_EXEC: + */ + if ((prot & PROT_READ) && (current->personality & READ_IMPLIES_EXEC)) + prot |= PROT_EXEC; + + vm_flags = calc_vm_prot_bits(prot); + + down_write(¤t->mm->mmap_sem); + + vma = find_vma(current->mm, start); + error = -ENOMEM; + if (!vma) + goto out; + prev = vma->vm_prev; + if (unlikely(grows & PROT_GROWSDOWN)) { + if (vma->vm_start >= end) + goto out; + start = vma->vm_start; + error = -EINVAL; + if (!(vma->vm_flags & VM_GROWSDOWN)) + goto out; + } else { + if (vma->vm_start > start) + goto out; + if (unlikely(grows & PROT_GROWSUP)) { + end = vma->vm_end; + error = -EINVAL; + if (!(vma->vm_flags & VM_GROWSUP)) + goto out; + } + } + if (start > vma->vm_start) + prev = vma; + + for (nstart = start ; ; ) { + unsigned long newflags; + + /* Here we know that vma->vm_start <= nstart < vma->vm_end. */ + + newflags = vm_flags; + newflags |= (vma->vm_flags & ~(VM_READ | VM_WRITE | VM_EXEC)); + + /* newflags >> 4 shift VM_MAY% in place of VM_% */ + if ((newflags & ~(newflags >> 4)) & (VM_READ | VM_WRITE | VM_EXEC)) { + error = -EACCES; + goto out; + } + + error = security_file_mprotect(vma, reqprot, prot); + if (error) + goto out; + + tmp = vma->vm_end; + if (tmp > end) + tmp = end; + error = mprotect_fixup(vma, &prev, nstart, tmp, newflags); + if (error) + goto out; + nstart = tmp; + + if (nstart < prev->vm_end) + nstart = prev->vm_end; + if (nstart >= end) + goto out; + + vma = prev->vm_next; + if (!vma || vma->vm_start != nstart) { + error = -ENOMEM; + goto out; + } + } +out: + up_write(¤t->mm->mmap_sem); + return error; +} -- cgit v1.2.3