// 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/pagewalk.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,
                unsigned long cp_flags)
{
        pte_t *pte, oldpte;
        spinlock_t *ptl;
        unsigned long pages = 0;
        int target_node = NUMA_NO_NODE;
        bool dirty_accountable = cp_flags & MM_CP_DIRTY_ACCT;
        bool prot_numa = cp_flags & MM_CP_PROT_NUMA;
        bool uffd_wp = cp_flags & MM_CP_UFFD_WP;
        bool uffd_wp_resolve = cp_flags & MM_CP_UFFD_WP_RESOLVE;

        /*
         * 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;

                                /* Avoid TLB flush if possible */
                                if (pte_protnone(oldpte))
                                        continue;

                                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_lru(page) && PageDirty(page))
                                        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;
                        }

                        oldpte = ptep_modify_prot_start(vma, addr, pte);
                        ptent = pte_modify(oldpte, newprot);
                        if (preserve_write)
                                ptent = pte_mk_savedwrite(ptent);

                        if (uffd_wp) {
                                ptent = pte_wrprotect(ptent);
                                ptent = pte_mkuffd_wp(ptent);
                        } else if (uffd_wp_resolve) {
                                /*
                                 * Leave the write bit to be handled
                                 * by PF interrupt handler, then
                                 * things like COW could be properly
                                 * handled.
                                 */
                                ptent = pte_clear_uffd_wp(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(vma, addr, pte, oldpte, ptent);
                        pages++;
                } else if (is_swap_pte(oldpte)) {
                        swp_entry_t entry = pte_to_swp_entry(oldpte);
                        pte_t newpte;

                        if (is_write_migration_entry(entry)) {
                                /*
                                 * 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);
                                if (pte_swp_uffd_wp(oldpte))
                                        newpte = pte_swp_mkuffd_wp(newpte);
                        } else if (is_write_device_private_entry(entry)) {
                                /*
                                 * We do not preserve soft-dirtiness. See
                                 * copy_one_pte() for explanation.
                                 */
                                make_device_private_entry_read(&entry);
                                newpte = swp_entry_to_pte(entry);
                                if (pte_swp_uffd_wp(oldpte))
                                        newpte = pte_swp_mkuffd_wp(newpte);
                        } else {
                                newpte = oldpte;
                        }

                        if (uffd_wp)
                                newpte = pte_swp_mkuffd_wp(newpte);
                        else if (uffd_wp_resolve)
                                newpte = pte_swp_clear_uffd_wp(newpte);

                        if (!pte_same(oldpte, newpte)) {
                                set_pte_at(vma->vm_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, unsigned long cp_flags)
{
        pmd_t *pmd;
        unsigned long next;
        unsigned long pages = 0;
        unsigned long nr_huge_updates = 0;
        struct mmu_notifier_range range;

        range.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 (!range.start) {
                        mmu_notifier_range_init(&range,
                                MMU_NOTIFY_PROTECTION_VMA, 0,
                                vma, vma->vm_mm, addr, end);
                        mmu_notifier_invalidate_range_start(&range);
                }

                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, cp_flags);

                                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,
                                              cp_flags);
                pages += this_pages;
next:
                cond_resched();
        } while (pmd++, addr = next, addr != end);

        if (range.start)
                mmu_notifier_invalidate_range_end(&range);

        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, unsigned long cp_flags)
{
        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,
                                          cp_flags);
        } 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, unsigned long cp_flags)
{
        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,
                                          cp_flags);
        } 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,
                unsigned long cp_flags)
{
        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,
                                          cp_flags);
        } 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,
                       unsigned long cp_flags)
{
        unsigned long pages;

        BUG_ON((cp_flags & MM_CP_UFFD_WP_ALL) == MM_CP_UFFD_WP_ALL);

        if (is_vm_hugetlb_page(vma))
                pages = hugetlb_change_protection(vma, start, end, newprot);
        else
                pages = change_protection_range(vma, start, end, newprot,
                                                cp_flags);

        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 const struct mm_walk_ops prot_none_walk_ops = {
        .pte_entry              = prot_none_pte_entry,
        .hugetlb_entry          = prot_none_hugetlb_entry,
        .test_walk              = prot_none_test,
};

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_ACCESS_FLAGS) == 0) {
                pgprot_t new_pgprot = vm_get_page_prot(newflags);

                error = walk_page_range(current->mm, start, end,
                                &prot_none_walk_ops, &new_pgprot);
                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 ? MM_CP_DIRTY_ACCT : 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);

        start = untagged_addr(start);

        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_ACCESS_FLAGS) {
                        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 */