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-rw-r--r--mm/mprotect.c329
1 files changed, 329 insertions, 0 deletions
diff --git a/mm/mprotect.c b/mm/mprotect.c
new file mode 100644
index 00000000..5a688a27
--- /dev/null
+++ b/mm/mprotect.c
@@ -0,0 +1,329 @@
+/*
+ * mm/mprotect.c
+ *
+ * (C) Copyright 1994 Linus Torvalds
+ * (C) Copyright 2002 Christoph Hellwig
+ *
+ * Address space accounting code <alan@lxorguk.ukuu.org.uk>
+ * (C) Copyright 2002 Red Hat Inc, All Rights Reserved
+ */
+
+#include <linux/mm.h>
+#include <linux/hugetlb.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 <linux/mmu_notifier.h>
+#include <linux/migrate.h>
+#include <linux/perf_event.h>
+#include <asm/uaccess.h>
+#include <asm/pgtable.h>
+#include <asm/cacheflush.h>
+#include <asm/tlbflush.h>
+
+#ifndef pgprot_modify
+static inline pgprot_t pgprot_modify(pgprot_t oldprot, pgprot_t newprot)
+{
+ return newprot;
+}
+#endif
+
+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);
+ arch_enter_lazy_mmu_mode();
+ do {
+ oldpte = *pte;
+ if (pte_present(oldpte)) {
+ pte_t ptent;
+
+ ptent = ptep_modify_prot_start(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);
+
+ ptep_modify_prot_commit(mm, addr, pte, ptent);
+ } else if (PAGE_MIGRATION && !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));
+ }
+ }
+ } while (pte++, addr += PAGE_SIZE, addr != end);
+ arch_leave_lazy_mmu_mode();
+ pte_unmap_unlock(pte - 1, ptl);
+}
+
+static inline void change_pmd_range(struct vm_area_struct *vma, 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_trans_huge(*pmd)) {
+ if (next - addr != HPAGE_PMD_SIZE)
+ split_huge_page_pmd(vma->vm_mm, pmd);
+ else if (change_huge_pmd(vma, pmd, addr, newprot))
+ continue;
+ /* fall through */
+ }
+ if (pmd_none_or_clear_bad(pmd))
+ continue;
+ change_pte_range(vma->vm_mm, pmd, addr, next, newprot,
+ dirty_accountable);
+ } while (pmd++, addr = next, addr != end);
+}
+
+static inline void change_pud_range(struct vm_area_struct *vma, 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(vma, 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(vma, pgd, addr, next, newprot,
+ dirty_accountable);
+ } while (pgd++, addr = next, addr != end);
+ flush_tlb_range(vma, start, end);
+}
+
+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(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 = pgprot_modify(vma->vm_page_prot,
+ vm_get_page_prot(newflags));
+
+ if (vma_wants_writenotify(vma)) {
+ vma->vm_page_prot = vm_get_page_prot(newflags & ~VM_SHARED);
+ dirty_accountable = 1;
+ }
+
+ mmu_notifier_invalidate_range_start(mm, start, end);
+ 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);
+ mmu_notifier_invalidate_range_end(mm, start, end);
+ 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(&current->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(&current->mm->mmap_sem);
+ return error;
+}