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-rw-r--r--mm/mprotect.c670
1 files changed, 670 insertions, 0 deletions
diff --git a/mm/mprotect.c b/mm/mprotect.c
new file mode 100644
index 000000000..86837f250
--- /dev/null
+++ b/mm/mprotect.c
@@ -0,0 +1,670 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * 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 <linux/pkeys.h>
+#include <linux/ksm.h>
+#include <linux/uaccess.h>
+#include <linux/mm_inline.h>
+#include <asm/pgtable.h>
+#include <asm/cacheflush.h>
+#include <asm/mmu_context.h>
+#include <asm/tlbflush.h>
+
+#include "internal.h"
+
+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;
+ int target_node = NUMA_NO_NODE;
+
+ /*
+ * Can be called with only the mmap_sem for reading by
+ * prot_numa so we must check the pmd isn't constantly
+ * changing from under us from pmd_none to pmd_trans_huge
+ * and/or the other way around.
+ */
+ if (pmd_trans_unstable(pmd))
+ return 0;
+
+ /*
+ * The pmd points to a regular pte so the pmd can't change
+ * from under us even if the mmap_sem is only hold for
+ * reading.
+ */
+ pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
+
+ /* Get target node for single threaded private VMAs */
+ if (prot_numa && !(vma->vm_flags & VM_SHARED) &&
+ atomic_read(&vma->vm_mm->mm_users) == 1)
+ target_node = numa_node_id();
+
+ flush_tlb_batched_pending(vma->vm_mm);
+ 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;
+
+ /* Also skip shared copy-on-write pages */
+ if (is_cow_mapping(vma->vm_flags) &&
+ page_mapcount(page) != 1)
+ continue;
+
+ /*
+ * While migration can move some dirty pages,
+ * it cannot move them all from MIGRATE_ASYNC
+ * context.
+ */
+ if (page_is_file_cache(page) && PageDirty(page))
+ continue;
+
+ /* Avoid TLB flush if possible */
+ if (pte_protnone(oldpte))
+ continue;
+
+ /*
+ * Don't mess with PTEs if page is already on the node
+ * a single-threaded process is running on.
+ */
+ if (target_node == page_to_nid(page))
+ continue;
+ }
+
+ ptent = ptep_modify_prot_start(mm, addr, pte);
+ ptent = pte_modify(ptent, newprot);
+ if (preserve_write)
+ ptent = pte_mk_savedwrite(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++;
+ }
+
+ if (is_write_device_private_entry(entry)) {
+ pte_t newpte;
+
+ /*
+ * We do not preserve soft-dirtiness. See
+ * copy_one_pte() for explanation.
+ */
+ make_device_private_entry_read(&entry);
+ newpte = swp_entry_to_pte(entry);
+ 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;
+}
+
+/*
+ * Used when setting automatic NUMA hinting protection where it is
+ * critical that a numa hinting PMD is not confused with a bad PMD.
+ */
+static inline int pmd_none_or_clear_bad_unless_trans_huge(pmd_t *pmd)
+{
+ pmd_t pmdval = pmd_read_atomic(pmd);
+
+ /* See pmd_none_or_trans_huge_or_clear_bad for info on barrier */
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+ barrier();
+#endif
+
+ if (pmd_none(pmdval))
+ return 1;
+ if (pmd_trans_huge(pmdval))
+ return 0;
+ if (unlikely(pmd_bad(pmdval))) {
+ pmd_clear_bad(pmd);
+ return 1;
+ }
+
+ return 0;
+}
+
+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);
+
+ /*
+ * Automatic NUMA balancing walks the tables with mmap_sem
+ * held for read. It's possible a parallel update to occur
+ * between pmd_trans_huge() and a pmd_none_or_clear_bad()
+ * check leading to a false positive and clearing.
+ * Hence, it's necessary to atomically read the PMD value
+ * for all the checks.
+ */
+ if (!is_swap_pmd(*pmd) && !pmd_devmap(*pmd) &&
+ pmd_none_or_clear_bad_unless_trans_huge(pmd))
+ goto next;
+
+ /* 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 (is_swap_pmd(*pmd) || pmd_trans_huge(*pmd) || pmd_devmap(*pmd)) {
+ if (next - addr != HPAGE_PMD_SIZE) {
+ __split_huge_pmd(vma, pmd, addr, false, NULL);
+ } 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 */
+ goto next;
+ }
+ }
+ /* 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;
+next:
+ cond_resched();
+ } 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,
+ p4d_t *p4d, 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(p4d, 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 inline unsigned long change_p4d_range(struct vm_area_struct *vma,
+ pgd_t *pgd, unsigned long addr, unsigned long end,
+ pgprot_t newprot, int dirty_accountable, int prot_numa)
+{
+ p4d_t *p4d;
+ unsigned long next;
+ unsigned long pages = 0;
+
+ p4d = p4d_offset(pgd, addr);
+ do {
+ next = p4d_addr_end(addr, end);
+ if (p4d_none_or_clear_bad(p4d))
+ continue;
+ pages += change_pud_range(vma, p4d, addr, next, newprot,
+ dirty_accountable, prot_numa);
+ } while (p4d++, 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);
+ inc_tlb_flush_pending(mm);
+ do {
+ next = pgd_addr_end(addr, end);
+ if (pgd_none_or_clear_bad(pgd))
+ continue;
+ pages += change_p4d_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);
+ dec_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;
+}
+
+static int prot_none_pte_entry(pte_t *pte, unsigned long addr,
+ unsigned long next, struct mm_walk *walk)
+{
+ return pfn_modify_allowed(pte_pfn(*pte), *(pgprot_t *)(walk->private)) ?
+ 0 : -EACCES;
+}
+
+static int prot_none_hugetlb_entry(pte_t *pte, unsigned long hmask,
+ unsigned long addr, unsigned long next,
+ struct mm_walk *walk)
+{
+ return pfn_modify_allowed(pte_pfn(*pte), *(pgprot_t *)(walk->private)) ?
+ 0 : -EACCES;
+}
+
+static int prot_none_test(unsigned long addr, unsigned long next,
+ struct mm_walk *walk)
+{
+ return 0;
+}
+
+static int prot_none_walk(struct vm_area_struct *vma, unsigned long start,
+ unsigned long end, unsigned long newflags)
+{
+ pgprot_t new_pgprot = vm_get_page_prot(newflags);
+ struct mm_walk prot_none_walk = {
+ .pte_entry = prot_none_pte_entry,
+ .hugetlb_entry = prot_none_hugetlb_entry,
+ .test_walk = prot_none_test,
+ .mm = current->mm,
+ .private = &new_pgprot,
+ };
+
+ return walk_page_range(start, end, &prot_none_walk);
+}
+
+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;
+ }
+
+ /*
+ * Do PROT_NONE PFN permission checks here when we can still
+ * bail out without undoing a lot of state. This is a rather
+ * uncommon case, so doesn't need to be very optimized.
+ */
+ if (arch_has_pfn_modify_check() &&
+ (vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) &&
+ (newflags & (VM_READ|VM_WRITE|VM_EXEC)) == 0) {
+ error = prot_none_walk(vma, start, end, newflags);
+ if (error)
+ return error;
+ }
+
+ /*
+ * 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) {
+ /* Check space limits when area turns into data. */
+ if (!may_expand_vm(mm, newflags, nrpages) &&
+ may_expand_vm(mm, oldflags, nrpages))
+ return -ENOMEM;
+ 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),
+ vma->vm_userfaultfd_ctx);
+ if (*pprev) {
+ vma = *pprev;
+ VM_WARN_ON((vma->vm_flags ^ newflags) & ~VM_SOFTDIRTY);
+ 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->vm_page_prot);
+ vma_set_page_prot(vma);
+
+ change_protection(vma, start, end, vma->vm_page_prot,
+ dirty_accountable, 0);
+
+ /*
+ * Private VM_LOCKED VMA becoming writable: trigger COW to avoid major
+ * fault on access.
+ */
+ if ((oldflags & (VM_WRITE | VM_SHARED | VM_LOCKED)) == VM_LOCKED &&
+ (newflags & VM_WRITE)) {
+ populate_vma_page_range(vma, start, end, NULL);
+ }
+
+ vm_stat_account(mm, oldflags, -nrpages);
+ vm_stat_account(mm, newflags, nrpages);
+ perf_event_mmap(vma);
+ return 0;
+
+fail:
+ vm_unacct_memory(charged);
+ return error;
+}
+
+/*
+ * pkey==-1 when doing a legacy mprotect()
+ */
+static int do_mprotect_pkey(unsigned long start, size_t len,
+ unsigned long prot, int pkey)
+{
+ unsigned long nstart, end, tmp, reqprot;
+ struct vm_area_struct *vma, *prev;
+ int error = -EINVAL;
+ const int grows = prot & (PROT_GROWSDOWN|PROT_GROWSUP);
+ const bool rier = (current->personality & READ_IMPLIES_EXEC) &&
+ (prot & PROT_READ);
+
+ 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, start))
+ return -EINVAL;
+
+ reqprot = prot;
+
+ if (down_write_killable(&current->mm->mmap_sem))
+ return -EINTR;
+
+ /*
+ * If userspace did not allocate the pkey, do not let
+ * them use it here.
+ */
+ error = -EINVAL;
+ if ((pkey != -1) && !mm_pkey_is_allocated(current->mm, pkey))
+ goto out;
+
+ 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 mask_off_old_flags;
+ unsigned long newflags;
+ int new_vma_pkey;
+
+ /* Here we know that vma->vm_start <= nstart < vma->vm_end. */
+
+ /* Does the application expect PROT_READ to imply PROT_EXEC */
+ if (rier && (vma->vm_flags & VM_MAYEXEC))
+ prot |= PROT_EXEC;
+
+ /*
+ * Each mprotect() call explicitly passes r/w/x permissions.
+ * If a permission is not passed to mprotect(), it must be
+ * cleared from the VMA.
+ */
+ mask_off_old_flags = VM_READ | VM_WRITE | VM_EXEC |
+ VM_FLAGS_CLEAR;
+
+ new_vma_pkey = arch_override_mprotect_pkey(vma, prot, pkey);
+ newflags = calc_vm_prot_bits(prot, new_vma_pkey);
+ newflags |= (vma->vm_flags & ~mask_off_old_flags);
+
+ /* 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;
+ }
+ prot = reqprot;
+ }
+out:
+ up_write(&current->mm->mmap_sem);
+ return error;
+}
+
+SYSCALL_DEFINE3(mprotect, unsigned long, start, size_t, len,
+ unsigned long, prot)
+{
+ return do_mprotect_pkey(start, len, prot, -1);
+}
+
+#ifdef CONFIG_ARCH_HAS_PKEYS
+
+SYSCALL_DEFINE4(pkey_mprotect, unsigned long, start, size_t, len,
+ unsigned long, prot, int, pkey)
+{
+ return do_mprotect_pkey(start, len, prot, pkey);
+}
+
+SYSCALL_DEFINE2(pkey_alloc, unsigned long, flags, unsigned long, init_val)
+{
+ int pkey;
+ int ret;
+
+ /* No flags supported yet. */
+ if (flags)
+ return -EINVAL;
+ /* check for unsupported init values */
+ if (init_val & ~PKEY_ACCESS_MASK)
+ return -EINVAL;
+
+ down_write(&current->mm->mmap_sem);
+ pkey = mm_pkey_alloc(current->mm);
+
+ ret = -ENOSPC;
+ if (pkey == -1)
+ goto out;
+
+ ret = arch_set_user_pkey_access(current, pkey, init_val);
+ if (ret) {
+ mm_pkey_free(current->mm, pkey);
+ goto out;
+ }
+ ret = pkey;
+out:
+ up_write(&current->mm->mmap_sem);
+ return ret;
+}
+
+SYSCALL_DEFINE1(pkey_free, int, pkey)
+{
+ int ret;
+
+ down_write(&current->mm->mmap_sem);
+ ret = mm_pkey_free(current->mm, pkey);
+ up_write(&current->mm->mmap_sem);
+
+ /*
+ * We could provie warnings or errors if any VMA still
+ * has the pkey set here.
+ */
+ return ret;
+}
+
+#endif /* CONFIG_ARCH_HAS_PKEYS */
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-29 22:18:07 +0000