diff options
Diffstat (limited to 'mm/mprotect.c')
| -rw-r--r-- | mm/mprotect.c | 1079 |
1 files changed, 1079 insertions, 0 deletions
diff --git a/mm/mprotect.c b/mm/mprotect.c new file mode 100644 index 000000000..2888ee638 --- /dev/null +++ b/mm/mprotect.c @@ -0,0 +1,1079 @@ +// 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 <linux/pgtable.h> +#include <linux/userfaultfd_k.h> +#include <uapi/linux/mman.h> +#include <asm/cacheflush.h> +#include <asm/mmu_context.h> +#include <asm/tlbflush.h> +#include <asm/tlb.h> + +#include "internal.h" + +static bool maybe_change_pte_writable(struct vm_area_struct *vma, pte_t pte) +{ + if (WARN_ON_ONCE(!vma_test(vma, VMA_WRITE_BIT))) + return false; + + /* Don't touch entries that are not even readable. */ + if (pte_protnone(pte)) + return false; + + /* Do we need write faults for softdirty tracking? */ + if (pte_needs_soft_dirty_wp(vma, pte)) + return false; + + /* Do we need write faults for uffd-wp tracking? */ + if (userfaultfd_pte_wp(vma, pte)) + return false; + + return true; +} + +static bool can_change_private_pte_writable(struct vm_area_struct *vma, + unsigned long addr, pte_t pte) +{ + struct page *page; + + if (!maybe_change_pte_writable(vma, pte)) + return false; + + /* + * Writable MAP_PRIVATE mapping: We can only special-case on + * exclusive anonymous pages, because we know that our + * write-fault handler similarly would map them writable without + * any additional checks while holding the PT lock. + */ + page = vm_normal_page(vma, addr, pte); + return page && PageAnon(page) && PageAnonExclusive(page); +} + +static bool can_change_shared_pte_writable(struct vm_area_struct *vma, + pte_t pte) +{ + if (!maybe_change_pte_writable(vma, pte)) + return false; + + VM_WARN_ON_ONCE(is_zero_pfn(pte_pfn(pte)) && pte_dirty(pte)); + + /* + * Writable MAP_SHARED mapping: "clean" might indicate that the FS still + * needs a real write-fault for writenotify + * (see vma_wants_writenotify()). If "dirty", the assumption is that the + * FS was already notified and we can simply mark the PTE writable + * just like the write-fault handler would do. + */ + return pte_dirty(pte); +} + +bool can_change_pte_writable(struct vm_area_struct *vma, unsigned long addr, + pte_t pte) +{ + if (!vma_test(vma, VMA_SHARED_BIT)) + return can_change_private_pte_writable(vma, addr, pte); + + return can_change_shared_pte_writable(vma, pte); +} + +static int mprotect_folio_pte_batch(struct folio *folio, pte_t *ptep, + pte_t pte, int max_nr_ptes, fpb_t flags) +{ + /* No underlying folio, so cannot batch */ + if (!folio) + return 1; + + if (!folio_test_large(folio)) + return 1; + + return folio_pte_batch_flags(folio, NULL, ptep, &pte, max_nr_ptes, flags); +} + +/* Set nr_ptes number of ptes, starting from idx */ +static __always_inline void prot_commit_flush_ptes(struct vm_area_struct *vma, + unsigned long addr, pte_t *ptep, pte_t oldpte, pte_t ptent, + int nr_ptes, int idx, bool set_write, struct mmu_gather *tlb) +{ + /* + * Advance the position in the batch by idx; note that if idx > 0, + * then the nr_ptes passed here is <= batch size - idx. + */ + addr += idx * PAGE_SIZE; + ptep += idx; + oldpte = pte_advance_pfn(oldpte, idx); + ptent = pte_advance_pfn(ptent, idx); + + if (set_write) + ptent = pte_mkwrite(ptent, vma); + + modify_prot_commit_ptes(vma, addr, ptep, oldpte, ptent, nr_ptes); + if (pte_needs_flush(oldpte, ptent)) + tlb_flush_pte_range(tlb, addr, nr_ptes * PAGE_SIZE); +} + +/* + * Get max length of consecutive ptes pointing to PageAnonExclusive() pages or + * !PageAnonExclusive() pages, starting from start_idx. Caller must enforce + * that the ptes point to consecutive pages of the same anon large folio. + */ +static __always_inline int page_anon_exclusive_batch(int start_idx, int max_len, + struct page *first_page, bool expected_anon_exclusive) +{ + int idx; + + for (idx = start_idx + 1; idx < start_idx + max_len; ++idx) { + if (expected_anon_exclusive != PageAnonExclusive(first_page + idx)) + break; + } + return idx - start_idx; +} + +/* + * This function is a result of trying our very best to retain the + * "avoid the write-fault handler" optimization. In can_change_pte_writable(), + * if the vma is a private vma, and we cannot determine whether to change + * the pte to writable just from the vma and the pte, we then need to look + * at the actual page pointed to by the pte. Unfortunately, if we have a + * batch of ptes pointing to consecutive pages of the same anon large folio, + * the anon-exclusivity (or the negation) of the first page does not guarantee + * the anon-exclusivity (or the negation) of the other pages corresponding to + * the pte batch; hence in this case it is incorrect to decide to change or + * not change the ptes to writable just by using information from the first + * pte of the batch. Therefore, we must individually check all pages and + * retrieve sub-batches. + */ +static __always_inline void commit_anon_folio_batch(struct vm_area_struct *vma, + struct folio *folio, struct page *first_page, unsigned long addr, pte_t *ptep, + pte_t oldpte, pte_t ptent, int nr_ptes, struct mmu_gather *tlb) +{ + bool expected_anon_exclusive; + int batch_idx = 0; + int len; + + while (nr_ptes) { + expected_anon_exclusive = PageAnonExclusive(first_page + batch_idx); + len = page_anon_exclusive_batch(batch_idx, nr_ptes, + first_page, expected_anon_exclusive); + prot_commit_flush_ptes(vma, addr, ptep, oldpte, ptent, len, + batch_idx, expected_anon_exclusive, tlb); + batch_idx += len; + nr_ptes -= len; + } +} + +static __always_inline void set_write_prot_commit_flush_ptes(struct vm_area_struct *vma, + struct folio *folio, struct page *page, unsigned long addr, pte_t *ptep, + pte_t oldpte, pte_t ptent, int nr_ptes, struct mmu_gather *tlb) +{ + bool set_write; + + if (vma_test(vma, VMA_SHARED_BIT)) { + set_write = can_change_shared_pte_writable(vma, ptent); + prot_commit_flush_ptes(vma, addr, ptep, oldpte, ptent, nr_ptes, + /* idx = */ 0, set_write, tlb); + return; + } + + set_write = maybe_change_pte_writable(vma, ptent) && + (folio && folio_test_anon(folio)); + if (!set_write) { + prot_commit_flush_ptes(vma, addr, ptep, oldpte, ptent, nr_ptes, + /* idx = */ 0, set_write, tlb); + return; + } + commit_anon_folio_batch(vma, folio, page, addr, ptep, oldpte, ptent, nr_ptes, tlb); +} + +static long change_softleaf_pte(struct vm_area_struct *vma, + unsigned long addr, pte_t *pte, pte_t oldpte, unsigned long cp_flags) +{ + const bool uffd_prot = cp_flags & (MM_CP_UFFD_WP | MM_CP_UFFD_RWP); + const bool uffd_prot_resolve = cp_flags & + (MM_CP_UFFD_WP_RESOLVE | MM_CP_UFFD_RWP_RESOLVE); + softleaf_t entry = softleaf_from_pte(oldpte); + pte_t newpte; + + if (softleaf_is_migration_write(entry)) { + const struct folio *folio = softleaf_to_folio(entry); + + /* + * A protection check is difficult so + * just be safe and disable write + */ + if (folio_test_anon(folio)) + entry = make_readable_exclusive_migration_entry(swp_offset(entry)); + else + entry = make_readable_migration_entry(swp_offset(entry)); + newpte = swp_entry_to_pte(entry); + if (pte_swp_soft_dirty(oldpte)) + newpte = pte_swp_mksoft_dirty(newpte); + } else if (softleaf_is_device_private_write(entry)) { + /* + * We do not preserve soft-dirtiness. See + * copy_nonpresent_pte() for explanation. + */ + entry = make_readable_device_private_entry(swp_offset(entry)); + newpte = swp_entry_to_pte(entry); + if (pte_swp_uffd(oldpte)) + newpte = pte_swp_mkuffd(newpte); + } else if (softleaf_is_marker(entry)) { + /* + * Ignore error swap entries unconditionally, + * because any access should sigbus/sigsegv + * anyway. + */ + if (softleaf_is_poison_marker(entry) || + softleaf_is_guard_marker(entry)) + return 0; + /* + * If this is uffd-wp pte marker and we'd like + * to unprotect it, drop it; the next page + * fault will trigger without uffd trapping. + */ + if (uffd_prot_resolve) { + pte_clear(vma->vm_mm, addr, pte); + return 1; + } + return 0; + } else { + newpte = oldpte; + } + + if (uffd_prot) + newpte = pte_swp_mkuffd(newpte); + else if (uffd_prot_resolve) + newpte = pte_swp_clear_uffd(newpte); + + if (!pte_same(oldpte, newpte)) { + set_pte_at(vma->vm_mm, addr, pte, newpte); + return 1; + } + return 0; +} + +static __always_inline void change_present_ptes(struct mmu_gather *tlb, + struct vm_area_struct *vma, unsigned long addr, pte_t *ptep, + int nr_ptes, unsigned long end, pgprot_t newprot, + struct folio *folio, struct page *page, unsigned long cp_flags) +{ + const bool uffd_prot = cp_flags & (MM_CP_UFFD_WP | MM_CP_UFFD_RWP); + const bool uffd_prot_resolve = cp_flags & + (MM_CP_UFFD_WP_RESOLVE | MM_CP_UFFD_RWP_RESOLVE); + pte_t ptent, oldpte; + + oldpte = modify_prot_start_ptes(vma, addr, ptep, nr_ptes); + ptent = pte_modify(oldpte, newprot); + + if (uffd_prot) + ptent = pte_mkuffd(ptent); + else if (uffd_prot_resolve) + ptent = pte_clear_uffd(ptent); + + /* + * The uffd bit on a VM_UFFD_RWP VMA carries PROT_NONE + * semantics. If mprotect() or NUMA hinting changed the + * base protection, restore PAGE_NONE so the PTE still + * traps on any access. pte_modify() preserves + * _PAGE_UFFD. + */ + if (userfaultfd_rwp(vma) && pte_uffd(ptent)) + ptent = pte_modify(ptent, PAGE_NONE); + + /* + * In some writable, shared mappings, we might want + * to catch actual write access -- see + * vma_wants_writenotify(). + * + * In all writable, private mappings, we have to + * properly handle COW. + * + * In both cases, we can sometimes still change PTEs + * writable and avoid the write-fault handler, for + * example, if a PTE is already dirty and no other + * COW or special handling is required. + */ + if ((cp_flags & MM_CP_TRY_CHANGE_WRITABLE) && + !pte_write(ptent)) + set_write_prot_commit_flush_ptes(vma, folio, page, + addr, ptep, oldpte, ptent, nr_ptes, tlb); + else + prot_commit_flush_ptes(vma, addr, ptep, oldpte, ptent, + nr_ptes, /* idx = */ 0, /* set_write = */ false, tlb); +} + +static long change_pte_range(struct mmu_gather *tlb, + 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; + long pages = 0; + bool is_private_single_threaded; + bool prot_numa = cp_flags & MM_CP_PROT_NUMA; + bool uffd_rwp = cp_flags & MM_CP_UFFD_RWP; + bool uffd_wp = cp_flags & MM_CP_UFFD_WP; + int nr_ptes; + + tlb_change_page_size(tlb, PAGE_SIZE); + pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl); + if (!pte) + return -EAGAIN; + + if (prot_numa) + is_private_single_threaded = vma_is_single_threaded_private(vma); + + flush_tlb_batched_pending(vma->vm_mm); + lazy_mmu_mode_enable(); + do { + nr_ptes = 1; + oldpte = ptep_get(pte); + if (pte_present(oldpte)) { + const fpb_t flags = FPB_RESPECT_SOFT_DIRTY | FPB_RESPECT_WRITE; + int max_nr_ptes = (end - addr) >> PAGE_SHIFT; + struct folio *folio = NULL; + struct page *page; + + /* Already in the desired state. */ + if (prot_numa && pte_protnone(oldpte)) + continue; + /* + * RWP-protected PTEs carry _PAGE_UFFD as a marker on + * top of PROT_NONE. Skip only entries already in that + * exact state; plain PROT_NONE from mprotect() still needs + * to be promoted so future faults can be distinguished. + */ + if (uffd_rwp && pte_protnone(oldpte) && pte_uffd(oldpte)) + continue; + + page = vm_normal_page(vma, addr, oldpte); + if (page) + folio = page_folio(page); + + /* + * Avoid trapping faults against the zero or KSM + * pages. See similar comment in change_huge_pmd. + * Skip this filter for uffd RWP which + * must set protnone regardless of NUMA placement. + */ + if (prot_numa && + !folio_can_map_prot_numa(folio, vma, + is_private_single_threaded)) { + + /* determine batch to skip */ + nr_ptes = mprotect_folio_pte_batch(folio, + pte, oldpte, max_nr_ptes, /* flags = */ 0); + continue; + } + + nr_ptes = mprotect_folio_pte_batch(folio, pte, oldpte, max_nr_ptes, flags); + + /* + * Optimize for the small-folio common case by + * special-casing it here. Compiler constant propagation + * plus copious amounts of __always_inline does wonders. + */ + if (likely(nr_ptes == 1)) { + change_present_ptes(tlb, vma, addr, pte, 1, + end, newprot, folio, page, cp_flags); + } else { + change_present_ptes(tlb, vma, addr, pte, + nr_ptes, end, newprot, folio, page, + cp_flags); + } + + pages += nr_ptes; + } else if (pte_none(oldpte)) { + /* + * Nobody plays with any none ptes besides + * userfaultfd when applying the protections. + */ + if (likely(!uffd_wp)) + continue; + + if (userfaultfd_wp_use_markers(vma)) { + /* + * For file-backed mem, we need to be able to + * wr-protect a none pte, because even if the + * pte is none, the page/swap cache could + * exist. Doing that by install a marker. + */ + set_pte_at(vma->vm_mm, addr, pte, + make_pte_marker(PTE_MARKER_UFFD_WP)); + pages++; + } + } else { + pages += change_softleaf_pte(vma, addr, pte, oldpte, cp_flags); + } + } while (pte += nr_ptes, addr += nr_ptes * PAGE_SIZE, addr != end); + lazy_mmu_mode_disable(); + pte_unmap_unlock(pte - 1, ptl); + + return pages; +} + +/* + * Return true if we want to split THPs into PTE mappings in change + * protection procedure, false otherwise. + */ +static inline bool +pgtable_split_needed(struct vm_area_struct *vma, unsigned long cp_flags) +{ + /* + * pte markers only resides in pte level, if we need pte markers, + * we need to split. For example, we cannot wr-protect a file thp + * (e.g. 2M shmem) because file thp is handled differently when + * split by erasing the pmd so far. + */ + return (cp_flags & (MM_CP_UFFD_WP | MM_CP_UFFD_RWP)) && !vma_is_anonymous(vma); +} + +/* + * Return true if we want to populate pgtables in change protection + * procedure, false otherwise + */ +static inline bool +pgtable_populate_needed(struct vm_area_struct *vma, unsigned long cp_flags) +{ + /* If not within ioctl(UFFDIO_WRITEPROTECT), then don't bother */ + if (!(cp_flags & MM_CP_UFFD_WP)) + return false; + + /* Populate if the userfaultfd mode requires pte markers */ + return userfaultfd_wp_use_markers(vma); +} + +/* + * Populate the pgtable underneath for whatever reason if requested. + * When {pte|pmd|...}_alloc() failed we treat it the same way as pgtable + * allocation failures during page faults by kicking OOM and returning + * error. + */ +#define change_pmd_prepare(vma, pmd, cp_flags) \ + ({ \ + long err = 0; \ + if (unlikely(pgtable_populate_needed(vma, cp_flags))) { \ + if (pte_alloc(vma->vm_mm, pmd)) \ + err = -ENOMEM; \ + } \ + err; \ + }) + +/* + * This is the general pud/p4d/pgd version of change_pmd_prepare(). We need to + * have separate change_pmd_prepare() because pte_alloc() returns 0 on success, + * while {pmd|pud|p4d}_alloc() returns the valid pointer on success. + */ +#define change_prepare(vma, high, low, addr, cp_flags) \ + ({ \ + long err = 0; \ + if (unlikely(pgtable_populate_needed(vma, cp_flags))) { \ + low##_t *p = low##_alloc(vma->vm_mm, high, addr); \ + if (p == NULL) \ + err = -ENOMEM; \ + } \ + err; \ + }) + +static inline long change_pmd_range(struct mmu_gather *tlb, + 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; + long pages = 0; + unsigned long nr_huge_updates = 0; + + pmd = pmd_offset(pud, addr); + do { + long ret; + pmd_t _pmd; +again: + next = pmd_addr_end(addr, end); + + ret = change_pmd_prepare(vma, pmd, cp_flags); + if (ret) { + pages = ret; + break; + } + + if (pmd_none(*pmd)) + goto next; + + _pmd = pmdp_get_lockless(pmd); + if (pmd_is_huge(_pmd)) { + if ((next - addr != HPAGE_PMD_SIZE) || + pgtable_split_needed(vma, cp_flags)) { + __split_huge_pmd(vma, pmd, addr, false); + /* + * For file-backed, the pmd could have been + * cleared; make sure pmd populated if + * necessary, then fall-through to pte level. + */ + ret = change_pmd_prepare(vma, pmd, cp_flags); + if (ret) { + pages = ret; + break; + } + } else { + ret = change_huge_pmd(tlb, vma, pmd, + addr, newprot, cp_flags); + if (ret) { + if (ret == HPAGE_PMD_NR) { + pages += HPAGE_PMD_NR; + nr_huge_updates++; + } + + /* huge pmd was handled */ + goto next; + } + } + /* fall through, the trans huge pmd just split */ + } + + ret = change_pte_range(tlb, vma, pmd, addr, next, newprot, + cp_flags); + if (ret < 0) + goto again; + pages += ret; +next: + cond_resched(); + } while (pmd++, addr = next, addr != end); + + if (nr_huge_updates) + count_vm_numa_events(NUMA_HUGE_PTE_UPDATES, nr_huge_updates); + return pages; +} + +static inline long change_pud_range(struct mmu_gather *tlb, + struct vm_area_struct *vma, p4d_t *p4d, unsigned long addr, + unsigned long end, pgprot_t newprot, unsigned long cp_flags) +{ + struct mmu_notifier_range range; + pud_t *pudp, pud; + unsigned long next; + long pages = 0, ret; + + range.start = 0; + + pudp = pud_offset(p4d, addr); + do { +again: + next = pud_addr_end(addr, end); + ret = change_prepare(vma, pudp, pmd, addr, cp_flags); + if (ret) { + pages = ret; + break; + } + + pud = pudp_get(pudp); + if (pud_none(pud)) + continue; + + if (!range.start) { + mmu_notifier_range_init(&range, + MMU_NOTIFY_PROTECTION_VMA, 0, + vma->vm_mm, addr, end); + mmu_notifier_invalidate_range_start(&range); + } + + if (pud_leaf(pud)) { + if ((next - addr != PUD_SIZE) || + pgtable_split_needed(vma, cp_flags)) { + __split_huge_pud(vma, pudp, addr); + goto again; + } else { + ret = change_huge_pud(tlb, vma, pudp, + addr, newprot, cp_flags); + if (ret == 0) + goto again; + /* huge pud was handled */ + if (ret == HPAGE_PUD_NR) + pages += HPAGE_PUD_NR; + continue; + } + } + + pages += change_pmd_range(tlb, vma, pudp, addr, next, newprot, + cp_flags); + } while (pudp++, addr = next, addr != end); + + if (range.start) + mmu_notifier_invalidate_range_end(&range); + + return pages; +} + +static inline long change_p4d_range(struct mmu_gather *tlb, + 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; + long pages = 0, ret; + + p4d = p4d_offset(pgd, addr); + do { + next = p4d_addr_end(addr, end); + ret = change_prepare(vma, p4d, pud, addr, cp_flags); + if (ret) + return ret; + if (p4d_none_or_clear_bad(p4d)) + continue; + pages += change_pud_range(tlb, vma, p4d, addr, next, newprot, + cp_flags); + } while (p4d++, addr = next, addr != end); + + return pages; +} + +static long change_protection_range(struct mmu_gather *tlb, + 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; + long pages = 0, ret; + + BUG_ON(addr >= end); + pgd = pgd_offset(mm, addr); + tlb_start_vma(tlb, vma); + do { + next = pgd_addr_end(addr, end); + ret = change_prepare(vma, pgd, p4d, addr, cp_flags); + if (ret) { + pages = ret; + break; + } + if (pgd_none_or_clear_bad(pgd)) + continue; + pages += change_p4d_range(tlb, vma, pgd, addr, next, newprot, + cp_flags); + } while (pgd++, addr = next, addr != end); + + tlb_end_vma(tlb, vma); + + return pages; +} + +long change_protection(struct mmu_gather *tlb, + struct vm_area_struct *vma, unsigned long start, + unsigned long end, unsigned long cp_flags) +{ + pgprot_t newprot = vma->vm_page_prot; + long pages; + + /* + * MM_CP_UFFD_{WP,RWP} and _RESOLVE are mutually exclusive within one + * change, and WP and RWP cannot mix. Miswired callers get a warn and + * a no-op; userspace cannot reach this state. + */ + if (WARN_ON_ONCE((cp_flags & MM_CP_UFFD_WP_ALL) == MM_CP_UFFD_WP_ALL || + (cp_flags & MM_CP_UFFD_RWP_ALL) == MM_CP_UFFD_RWP_ALL || + ((cp_flags & MM_CP_UFFD_WP_ALL) && + (cp_flags & MM_CP_UFFD_RWP_ALL)))) + return 0; + +#ifdef CONFIG_NUMA_BALANCING + /* + * Ordinary protection updates (mprotect, uffd-wp, softdirty tracking) + * are expected to reflect their requirements via VMA flags such that + * vma_set_page_prot() will adjust vma->vm_page_prot accordingly. + */ + if (cp_flags & MM_CP_PROT_NUMA) + newprot = PAGE_NONE; +#else + WARN_ON_ONCE(cp_flags & MM_CP_PROT_NUMA); +#endif + + if (IS_ENABLED(CONFIG_ARCH_HAS_PTE_PROTNONE) && + (cp_flags & MM_CP_UFFD_RWP)) + newprot = PAGE_NONE; + + if (is_vm_hugetlb_page(vma)) + pages = hugetlb_change_protection(vma, start, end, newprot, + cp_flags); + else + pages = change_protection_range(tlb, 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(ptep_get(pte)), + *(pgprot_t *)(walk->private)) ? + 0 : -EACCES; +} + +#ifdef CONFIG_HUGETLB_PAGE +static int prot_none_hugetlb_entry(pte_t *pte, unsigned long hmask, + unsigned long addr, unsigned long next, + struct mm_walk *walk) +{ + const pte_t entry = huge_ptep_get(walk->mm, addr, pte); + + if (pfn_modify_allowed(pte_pfn(entry), *(pgprot_t *)(walk->private))) + return 0; + return -EACCES; +} +#else +#define prot_none_hugetlb_entry NULL +#endif + +static const struct mm_walk_ops prot_none_walk_ops = { + .pte_entry = prot_none_pte_entry, + .hugetlb_entry = prot_none_hugetlb_entry, + .walk_lock = PGWALK_WRLOCK, +}; + +int +mprotect_fixup(struct vma_iterator *vmi, struct mmu_gather *tlb, + struct vm_area_struct *vma, struct vm_area_struct **pprev, + unsigned long start, unsigned long end, vm_flags_t newflags) +{ + struct mm_struct *mm = vma->vm_mm; + const vma_flags_t old_vma_flags = READ_ONCE(vma->flags); + vma_flags_t new_vma_flags = legacy_to_vma_flags(newflags); + long nrpages = (end - start) >> PAGE_SHIFT; + unsigned int mm_cp_flags = 0; + unsigned long charged = 0; + int error; + + if (vma_is_sealed(vma)) + return -EPERM; + + if (vma_flags_same_pair(&old_vma_flags, &new_vma_flags)) { + *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_flags_test_any(&old_vma_flags, VMA_PFNMAP_BIT, + VMA_MIXEDMAP_BIT) && + !vma_flags_test_any_mask(&new_vma_flags, VMA_ACCESS_FLAGS)) { + pgprot_t new_pgprot = vm_get_page_prot(newflags); + + error = walk_page_range_vma(vma, 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 except in the anonymous case where no + * anon_vma has yet to be assigned. + * + * hugetlb mapping were accounted for even if read-only so there is + * no need to account for them here. + */ + if (vma_flags_test(&new_vma_flags, VMA_WRITE_BIT)) { + /* Check space limits when area turns into data. */ + if (!may_expand_vm(mm, &new_vma_flags, nrpages) && + may_expand_vm(mm, &old_vma_flags, nrpages)) + return -ENOMEM; + if (!vma_flags_test_any(&old_vma_flags, + VMA_ACCOUNT_BIT, VMA_WRITE_BIT, VMA_HUGETLB_BIT, + VMA_SHARED_BIT, VMA_NORESERVE_BIT)) { + charged = nrpages; + if (security_vm_enough_memory_mm(mm, charged)) + return -ENOMEM; + vma_flags_set(&new_vma_flags, VMA_ACCOUNT_BIT); + } + } else if (vma_flags_test(&old_vma_flags, VMA_ACCOUNT_BIT) && + vma_is_anonymous(vma) && !vma->anon_vma) { + vma_flags_clear(&new_vma_flags, VMA_ACCOUNT_BIT); + } + + vma = vma_modify_flags(vmi, *pprev, vma, start, end, &new_vma_flags); + if (IS_ERR(vma)) { + error = PTR_ERR(vma); + goto fail; + } + + *pprev = vma; + + /* + * vm_flags and vm_page_prot are protected by the mmap_lock + * held in write mode. + */ + vma_start_write(vma); + vma_flags_reset_once(vma, &new_vma_flags); + if (vma_wants_manual_pte_write_upgrade(vma)) + mm_cp_flags |= MM_CP_TRY_CHANGE_WRITABLE; + vma_set_page_prot(vma); + + change_protection(tlb, vma, start, end, mm_cp_flags); + + if (vma_flags_test(&old_vma_flags, VMA_ACCOUNT_BIT) && + !vma_flags_test(&new_vma_flags, VMA_ACCOUNT_BIT)) + vm_unacct_memory(nrpages); + + /* + * Private VMA_LOCKED_BIT VMA becoming writable: trigger COW to avoid + * major fault on access. + */ + if (vma_flags_test(&new_vma_flags, VMA_WRITE_BIT) && + vma_flags_test(&old_vma_flags, VMA_LOCKED_BIT) && + !vma_flags_test_any(&old_vma_flags, VMA_WRITE_BIT, VMA_SHARED_BIT)) + populate_vma_page_range(vma, start, end, NULL); + + vm_stat_account(mm, vma_flags_to_legacy(old_vma_flags), -nrpages); + newflags = vma_flags_to_legacy(new_vma_flags); + 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; + const int grows = prot & (PROT_GROWSDOWN|PROT_GROWSUP); + const bool rier = (current->personality & READ_IMPLIES_EXEC) && + (prot & PROT_READ); + struct mmu_gather tlb; + struct vma_iterator vmi; + + 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 (mmap_write_lock_killable(current->mm)) + 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_iter_init(&vmi, current->mm, start); + vma = vma_find(&vmi, end); + 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_test(vma, VMA_GROWSDOWN_BIT)) + goto out; + } else { + if (vma->vm_start > start) + goto out; + if (unlikely(grows & PROT_GROWSUP)) { + end = vma->vm_end; + error = -EINVAL; + if (!vma_test_single_mask(vma, VMA_GROWSUP)) + goto out; + } + } + + prev = vma_prev(&vmi); + if (start > vma->vm_start) + prev = vma; + + tlb_gather_mmu(&tlb, current->mm); + nstart = start; + tmp = vma->vm_start; + for_each_vma_range(vmi, vma, end) { + vm_flags_t mask_off_old_flags; + vma_flags_t new_vma_flags; + vm_flags_t newflags; + int new_vma_pkey; + + if (vma->vm_start != tmp) { + error = -ENOMEM; + break; + } + + /* Does the application expect PROT_READ to imply PROT_EXEC */ + if (rier && vma_test(vma, VMA_MAYEXEC_BIT)) + 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_ACCESS_FLAGS | 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); + new_vma_flags = legacy_to_vma_flags(newflags); + + /* newflags >> 4 shift VM_MAY% in place of VM_% */ + if ((newflags & ~(newflags >> 4)) & VM_ACCESS_FLAGS) { + error = -EACCES; + break; + } + + if (map_deny_write_exec(&vma->flags, &new_vma_flags)) { + error = -EACCES; + break; + } + + /* Allow architectures to sanity-check the new flags */ + if (!arch_validate_flags(newflags)) { + error = -EINVAL; + break; + } + + error = security_file_mprotect(vma, reqprot, prot); + if (error) + break; + + tmp = vma->vm_end; + if (tmp > end) + tmp = end; + + if (vma->vm_ops && vma->vm_ops->mprotect) { + error = vma->vm_ops->mprotect(vma, nstart, tmp, newflags); + if (error) + break; + } + + error = mprotect_fixup(&vmi, &tlb, vma, &prev, nstart, tmp, newflags); + if (error) + break; + + tmp = vma_iter_end(&vmi); + nstart = tmp; + prot = reqprot; + } + tlb_finish_mmu(&tlb); + + if (!error && tmp < end) + error = -ENOMEM; + +out: + mmap_write_unlock(current->mm); + 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; + + mmap_write_lock(current->mm); + pkey = mm_pkey_alloc(current->mm); + + ret = -ENOSPC; + if (pkey == -1) + goto out; + + ret = arch_set_user_pkey_access(pkey, init_val); + if (ret) { + mm_pkey_free(current->mm, pkey); + goto out; + } + ret = pkey; +out: + mmap_write_unlock(current->mm); + return ret; +} + +SYSCALL_DEFINE1(pkey_free, int, pkey) +{ + int ret; + + mmap_write_lock(current->mm); + ret = mm_pkey_free(current->mm, pkey); + mmap_write_unlock(current->mm); + + /* + * We could provide warnings or errors if any VMA still + * has the pkey set here. + */ + return ret; +} + +#endif /* CONFIG_ARCH_HAS_PKEYS */ |