/* * mm/mprotect.c * * (C) Copyright 1994 Linus Torvalds * (C) Copyright 2002 Christoph Hellwig * * Address space accounting code <alan@redhat.com> * (C) Copyright 2002 Red Hat Inc, All Rights Reserved */ #include <linux/mm.h> #include <linux/hugetlb.h> #include <linux/slab.h> #include <linux/shm.h> #include <linux/mman.h> #include <linux/fs.h> #include <linux/highmem.h> #include <linux/security.h> #include <linux/mempolicy.h> #include <linux/personality.h> #include <linux/syscalls.h> #include <linux/swap.h> #include <linux/swapops.h> #include <asm/uaccess.h> #include <asm/pgtable.h> #include <asm/cacheflush.h> #include <asm/tlbflush.h> static void change_pte_range(struct mm_struct *mm, pmd_t *pmd, unsigned long addr, unsigned long end, pgprot_t newprot, int dirty_accountable) { pte_t *pte, oldpte; spinlock_t *ptl; pte = pte_offset_map_lock(mm, pmd, addr, &ptl); do { oldpte = *pte; if (pte_present(oldpte)) { pte_t ptent; /* Avoid an SMP race with hardware updated dirty/clean * bits by wiping the pte and then setting the new pte * into place. */ ptent = ptep_get_and_clear(mm, addr, pte); ptent = pte_modify(ptent, newprot); /* * Avoid taking write faults for pages we know to be * dirty. */ if (dirty_accountable && pte_dirty(ptent)) ptent = pte_mkwrite(ptent); set_pte_at(mm, addr, pte, ptent); lazy_mmu_prot_update(ptent); #ifdef CONFIG_MIGRATION } else if (!pte_file(oldpte)) { swp_entry_t entry = pte_to_swp_entry(oldpte); if (is_write_migration_entry(entry)) { /* * A protection check is difficult so * just be safe and disable write */ make_migration_entry_read(&entry); set_pte_at(mm, addr, pte, swp_entry_to_pte(entry)); } #endif } } while (pte++, addr += PAGE_SIZE, addr != end); pte_unmap_unlock(pte - 1, ptl); } static inline void change_pmd_range(struct mm_struct *mm, pud_t *pud, unsigned long addr, unsigned long end, pgprot_t newprot, int dirty_accountable) { pmd_t *pmd; unsigned long next; pmd = pmd_offset(pud, addr); do { next = pmd_addr_end(addr, end); if (pmd_none_or_clear_bad(pmd)) continue; change_pte_range(mm, pmd, addr, next, newprot, dirty_accountable); } while (pmd++, addr = next, addr != end); } static inline void change_pud_range(struct mm_struct *mm, pgd_t *pgd, unsigned long addr, unsigned long end, pgprot_t newprot, int dirty_accountable) { pud_t *pud; unsigned long next; pud = pud_offset(pgd, addr); do { next = pud_addr_end(addr, end); if (pud_none_or_clear_bad(pud)) continue; change_pmd_range(mm, pud, addr, next, newprot, dirty_accountable); } while (pud++, addr = next, addr != end); } static void change_protection(struct vm_area_struct *vma, unsigned long addr, unsigned long end, pgprot_t newprot, int dirty_accountable) { struct mm_struct *mm = vma->vm_mm; pgd_t *pgd; unsigned long next; unsigned long start = addr; BUG_ON(addr >= end); pgd = pgd_offset(mm, addr); flush_cache_range(vma, addr, end); do { next = pgd_addr_end(addr, end); if (pgd_none_or_clear_bad(pgd)) continue; change_pud_range(mm, pgd, addr, next, newprot, dirty_accountable); } while (pgd++, addr = next, addr != end); flush_tlb_range(vma, start, end); } static 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. * * FIXME? We haven't defined a VM_NORESERVE flag, so mprotecting * a MAP_NORESERVE private mapping to writable will now reserve. */ if (newflags & VM_WRITE) { if (!(oldflags & (VM_ACCOUNT|VM_WRITE|VM_SHARED))) { charged = nrpages; if (security_vm_enough_memory(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; vma->vm_page_prot = protection_map[newflags & (VM_READ|VM_WRITE|VM_EXEC|VM_SHARED)]; if (vma_wants_writenotify(vma)) { vma->vm_page_prot = protection_map[newflags & (VM_READ|VM_WRITE|VM_EXEC)]; dirty_accountable = 1; } if (is_vm_hugetlb_page(vma)) hugetlb_change_protection(vma, start, end, vma->vm_page_prot); else change_protection(vma, start, end, vma->vm_page_prot, dirty_accountable); vm_stat_account(mm, oldflags, vma->vm_file, -nrpages); vm_stat_account(mm, newflags, vma->vm_file, nrpages); return 0; fail: vm_unacct_memory(charged); return error; } asmlinkage long sys_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 (prot & ~(PROT_READ | PROT_WRITE | PROT_EXEC | PROT_SEM)) 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_prev(current->mm, start, &prev); error = -ENOMEM; if (!vma) goto out; 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 | (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; }