diff options
Diffstat (limited to 'mm/mprotect.c')
| -rw-r--r-- | mm/mprotect.c | 282 |
1 files changed, 282 insertions, 0 deletions
diff --git a/mm/mprotect.c b/mm/mprotect.c new file mode 100644 index 00000000000..e9fbd013ad9 --- /dev/null +++ b/mm/mprotect.c @@ -0,0 +1,282 @@ +/* + * 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 <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) +{ + pte_t *pte; + + pte = pte_offset_map(pmd, addr); + do { + if (pte_present(*pte)) { + 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 = pte_modify(ptep_get_and_clear(mm, addr, pte), newprot); + set_pte_at(mm, addr, pte, ptent); + lazy_mmu_prot_update(ptent); + } + } while (pte++, addr += PAGE_SIZE, addr != end); + pte_unmap(pte - 1); +} + +static inline void change_pmd_range(struct mm_struct *mm, pud_t *pud, + unsigned long addr, unsigned long end, pgprot_t newprot) +{ + 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); + } 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) +{ + 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); + } while (pud++, addr = next, addr != end); +} + +static void change_protection(struct vm_area_struct *vma, + unsigned long addr, unsigned long end, pgprot_t newprot) +{ + 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); + spin_lock(&mm->page_table_lock); + do { + next = pgd_addr_end(addr, end); + if (pgd_none_or_clear_bad(pgd)) + continue; + change_pud_range(mm, pgd, addr, next, newprot); + } while (pgd++, addr = next, addr != end); + flush_tlb_range(vma, start, end); + spin_unlock(&mm->page_table_lock); +} + +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; + pgprot_t newprot; + pgoff_t pgoff; + int error; + + 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|VM_HUGETLB))) { + charged = nrpages; + if (security_vm_enough_memory(charged)) + return -ENOMEM; + newflags |= VM_ACCOUNT; + } + } + + newprot = protection_map[newflags & 0xf]; + + /* + * 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 = newprot; + change_protection(vma, start, end, newprot); + __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 (unlikely((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. */ + + if (is_vm_hugetlb_page(vma)) { + error = -EACCES; + goto out; + } + + newflags = vm_flags | (vma->vm_flags & ~(VM_READ | VM_WRITE | VM_EXEC)); + + if ((newflags & ~(newflags >> 4)) & 0xf) { + 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; +} |