Root/mm/mprotect.c

1/*
2 * mm/mprotect.c
3 *
4 * (C) Copyright 1994 Linus Torvalds
5 * (C) Copyright 2002 Christoph Hellwig
6 *
7 * Address space accounting code <alan@lxorguk.ukuu.org.uk>
8 * (C) Copyright 2002 Red Hat Inc, All Rights Reserved
9 */
10
11#include <linux/mm.h>
12#include <linux/hugetlb.h>
13#include <linux/shm.h>
14#include <linux/mman.h>
15#include <linux/fs.h>
16#include <linux/highmem.h>
17#include <linux/security.h>
18#include <linux/mempolicy.h>
19#include <linux/personality.h>
20#include <linux/syscalls.h>
21#include <linux/swap.h>
22#include <linux/swapops.h>
23#include <linux/mmu_notifier.h>
24#include <linux/migrate.h>
25#include <linux/perf_event.h>
26#include <asm/uaccess.h>
27#include <asm/pgtable.h>
28#include <asm/cacheflush.h>
29#include <asm/tlbflush.h>
30
31#ifndef pgprot_modify
32static inline pgprot_t pgprot_modify(pgprot_t oldprot, pgprot_t newprot)
33{
34    return newprot;
35}
36#endif
37
38static unsigned long change_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
39        unsigned long addr, unsigned long end, pgprot_t newprot,
40        int dirty_accountable, int prot_numa, bool *ret_all_same_node)
41{
42    struct mm_struct *mm = vma->vm_mm;
43    pte_t *pte, oldpte;
44    spinlock_t *ptl;
45    unsigned long pages = 0;
46    bool all_same_node = true;
47    int last_nid = -1;
48
49    pte = pte_offset_map_lock(mm, pmd, addr, &ptl);
50    arch_enter_lazy_mmu_mode();
51    do {
52        oldpte = *pte;
53        if (pte_present(oldpte)) {
54            pte_t ptent;
55            bool updated = false;
56
57            ptent = ptep_modify_prot_start(mm, addr, pte);
58            if (!prot_numa) {
59                ptent = pte_modify(ptent, newprot);
60                updated = true;
61            } else {
62                struct page *page;
63
64                page = vm_normal_page(vma, addr, oldpte);
65                if (page) {
66                    int this_nid = page_to_nid(page);
67                    if (last_nid == -1)
68                        last_nid = this_nid;
69                    if (last_nid != this_nid)
70                        all_same_node = false;
71
72                    /* only check non-shared pages */
73                    if (!pte_numa(oldpte) &&
74                        page_mapcount(page) == 1) {
75                        ptent = pte_mknuma(ptent);
76                        updated = true;
77                    }
78                }
79            }
80
81            /*
82             * Avoid taking write faults for pages we know to be
83             * dirty.
84             */
85            if (dirty_accountable && pte_dirty(ptent)) {
86                ptent = pte_mkwrite(ptent);
87                updated = true;
88            }
89
90            if (updated)
91                pages++;
92            ptep_modify_prot_commit(mm, addr, pte, ptent);
93        } else if (IS_ENABLED(CONFIG_MIGRATION) && !pte_file(oldpte)) {
94            swp_entry_t entry = pte_to_swp_entry(oldpte);
95
96            if (is_write_migration_entry(entry)) {
97                pte_t newpte;
98                /*
99                 * A protection check is difficult so
100                 * just be safe and disable write
101                 */
102                make_migration_entry_read(&entry);
103                newpte = swp_entry_to_pte(entry);
104                if (pte_swp_soft_dirty(oldpte))
105                    newpte = pte_swp_mksoft_dirty(newpte);
106                set_pte_at(mm, addr, pte, newpte);
107            }
108            pages++;
109        }
110    } while (pte++, addr += PAGE_SIZE, addr != end);
111    arch_leave_lazy_mmu_mode();
112    pte_unmap_unlock(pte - 1, ptl);
113
114    *ret_all_same_node = all_same_node;
115    return pages;
116}
117
118#ifdef CONFIG_NUMA_BALANCING
119static inline void change_pmd_protnuma(struct mm_struct *mm, unsigned long addr,
120                       pmd_t *pmd)
121{
122    spin_lock(&mm->page_table_lock);
123    set_pmd_at(mm, addr & PMD_MASK, pmd, pmd_mknuma(*pmd));
124    spin_unlock(&mm->page_table_lock);
125}
126#else
127static inline void change_pmd_protnuma(struct mm_struct *mm, unsigned long addr,
128                       pmd_t *pmd)
129{
130    BUG();
131}
132#endif /* CONFIG_NUMA_BALANCING */
133
134static inline unsigned long change_pmd_range(struct vm_area_struct *vma,
135        pud_t *pud, unsigned long addr, unsigned long end,
136        pgprot_t newprot, int dirty_accountable, int prot_numa)
137{
138    pmd_t *pmd;
139    unsigned long next;
140    unsigned long pages = 0;
141    bool all_same_node;
142
143    pmd = pmd_offset(pud, addr);
144    do {
145        next = pmd_addr_end(addr, end);
146        if (pmd_trans_huge(*pmd)) {
147            if (next - addr != HPAGE_PMD_SIZE)
148                split_huge_page_pmd(vma, addr, pmd);
149            else if (change_huge_pmd(vma, pmd, addr, newprot,
150                         prot_numa)) {
151                pages++;
152                continue;
153            }
154            /* fall through */
155        }
156        if (pmd_none_or_clear_bad(pmd))
157            continue;
158        pages += change_pte_range(vma, pmd, addr, next, newprot,
159                 dirty_accountable, prot_numa, &all_same_node);
160
161        /*
162         * If we are changing protections for NUMA hinting faults then
163         * set pmd_numa if the examined pages were all on the same
164         * node. This allows a regular PMD to be handled as one fault
165         * and effectively batches the taking of the PTL
166         */
167        if (prot_numa && all_same_node)
168            change_pmd_protnuma(vma->vm_mm, addr, pmd);
169    } while (pmd++, addr = next, addr != end);
170
171    return pages;
172}
173
174static inline unsigned long change_pud_range(struct vm_area_struct *vma,
175        pgd_t *pgd, unsigned long addr, unsigned long end,
176        pgprot_t newprot, int dirty_accountable, int prot_numa)
177{
178    pud_t *pud;
179    unsigned long next;
180    unsigned long pages = 0;
181
182    pud = pud_offset(pgd, addr);
183    do {
184        next = pud_addr_end(addr, end);
185        if (pud_none_or_clear_bad(pud))
186            continue;
187        pages += change_pmd_range(vma, pud, addr, next, newprot,
188                 dirty_accountable, prot_numa);
189    } while (pud++, addr = next, addr != end);
190
191    return pages;
192}
193
194static unsigned long change_protection_range(struct vm_area_struct *vma,
195        unsigned long addr, unsigned long end, pgprot_t newprot,
196        int dirty_accountable, int prot_numa)
197{
198    struct mm_struct *mm = vma->vm_mm;
199    pgd_t *pgd;
200    unsigned long next;
201    unsigned long start = addr;
202    unsigned long pages = 0;
203
204    BUG_ON(addr >= end);
205    pgd = pgd_offset(mm, addr);
206    flush_cache_range(vma, addr, end);
207    do {
208        next = pgd_addr_end(addr, end);
209        if (pgd_none_or_clear_bad(pgd))
210            continue;
211        pages += change_pud_range(vma, pgd, addr, next, newprot,
212                 dirty_accountable, prot_numa);
213    } while (pgd++, addr = next, addr != end);
214
215    /* Only flush the TLB if we actually modified any entries: */
216    if (pages)
217        flush_tlb_range(vma, start, end);
218
219    return pages;
220}
221
222unsigned long change_protection(struct vm_area_struct *vma, unsigned long start,
223               unsigned long end, pgprot_t newprot,
224               int dirty_accountable, int prot_numa)
225{
226    struct mm_struct *mm = vma->vm_mm;
227    unsigned long pages;
228
229    mmu_notifier_invalidate_range_start(mm, start, end);
230    if (is_vm_hugetlb_page(vma))
231        pages = hugetlb_change_protection(vma, start, end, newprot);
232    else
233        pages = change_protection_range(vma, start, end, newprot, dirty_accountable, prot_numa);
234    mmu_notifier_invalidate_range_end(mm, start, end);
235
236    return pages;
237}
238
239int
240mprotect_fixup(struct vm_area_struct *vma, struct vm_area_struct **pprev,
241    unsigned long start, unsigned long end, unsigned long newflags)
242{
243    struct mm_struct *mm = vma->vm_mm;
244    unsigned long oldflags = vma->vm_flags;
245    long nrpages = (end - start) >> PAGE_SHIFT;
246    unsigned long charged = 0;
247    pgoff_t pgoff;
248    int error;
249    int dirty_accountable = 0;
250
251    if (newflags == oldflags) {
252        *pprev = vma;
253        return 0;
254    }
255
256    /*
257     * If we make a private mapping writable we increase our commit;
258     * but (without finer accounting) cannot reduce our commit if we
259     * make it unwritable again. hugetlb mapping were accounted for
260     * even if read-only so there is no need to account for them here
261     */
262    if (newflags & VM_WRITE) {
263        if (!(oldflags & (VM_ACCOUNT|VM_WRITE|VM_HUGETLB|
264                        VM_SHARED|VM_NORESERVE))) {
265            charged = nrpages;
266            if (security_vm_enough_memory_mm(mm, charged))
267                return -ENOMEM;
268            newflags |= VM_ACCOUNT;
269        }
270    }
271
272    /*
273     * First try to merge with previous and/or next vma.
274     */
275    pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT);
276    *pprev = vma_merge(mm, *pprev, start, end, newflags,
277            vma->anon_vma, vma->vm_file, pgoff, vma_policy(vma));
278    if (*pprev) {
279        vma = *pprev;
280        goto success;
281    }
282
283    *pprev = vma;
284
285    if (start != vma->vm_start) {
286        error = split_vma(mm, vma, start, 1);
287        if (error)
288            goto fail;
289    }
290
291    if (end != vma->vm_end) {
292        error = split_vma(mm, vma, end, 0);
293        if (error)
294            goto fail;
295    }
296
297success:
298    /*
299     * vm_flags and vm_page_prot are protected by the mmap_sem
300     * held in write mode.
301     */
302    vma->vm_flags = newflags;
303    vma->vm_page_prot = pgprot_modify(vma->vm_page_prot,
304                      vm_get_page_prot(newflags));
305
306    if (vma_wants_writenotify(vma)) {
307        vma->vm_page_prot = vm_get_page_prot(newflags & ~VM_SHARED);
308        dirty_accountable = 1;
309    }
310
311    change_protection(vma, start, end, vma->vm_page_prot,
312              dirty_accountable, 0);
313
314    vm_stat_account(mm, oldflags, vma->vm_file, -nrpages);
315    vm_stat_account(mm, newflags, vma->vm_file, nrpages);
316    perf_event_mmap(vma);
317    return 0;
318
319fail:
320    vm_unacct_memory(charged);
321    return error;
322}
323
324SYSCALL_DEFINE3(mprotect, unsigned long, start, size_t, len,
325        unsigned long, prot)
326{
327    unsigned long vm_flags, nstart, end, tmp, reqprot;
328    struct vm_area_struct *vma, *prev;
329    int error = -EINVAL;
330    const int grows = prot & (PROT_GROWSDOWN|PROT_GROWSUP);
331    prot &= ~(PROT_GROWSDOWN|PROT_GROWSUP);
332    if (grows == (PROT_GROWSDOWN|PROT_GROWSUP)) /* can't be both */
333        return -EINVAL;
334
335    if (start & ~PAGE_MASK)
336        return -EINVAL;
337    if (!len)
338        return 0;
339    len = PAGE_ALIGN(len);
340    end = start + len;
341    if (end <= start)
342        return -ENOMEM;
343    if (!arch_validate_prot(prot))
344        return -EINVAL;
345
346    reqprot = prot;
347    /*
348     * Does the application expect PROT_READ to imply PROT_EXEC:
349     */
350    if ((prot & PROT_READ) && (current->personality & READ_IMPLIES_EXEC))
351        prot |= PROT_EXEC;
352
353    vm_flags = calc_vm_prot_bits(prot);
354
355    down_write(&current->mm->mmap_sem);
356
357    vma = find_vma(current->mm, start);
358    error = -ENOMEM;
359    if (!vma)
360        goto out;
361    prev = vma->vm_prev;
362    if (unlikely(grows & PROT_GROWSDOWN)) {
363        if (vma->vm_start >= end)
364            goto out;
365        start = vma->vm_start;
366        error = -EINVAL;
367        if (!(vma->vm_flags & VM_GROWSDOWN))
368            goto out;
369    } else {
370        if (vma->vm_start > start)
371            goto out;
372        if (unlikely(grows & PROT_GROWSUP)) {
373            end = vma->vm_end;
374            error = -EINVAL;
375            if (!(vma->vm_flags & VM_GROWSUP))
376                goto out;
377        }
378    }
379    if (start > vma->vm_start)
380        prev = vma;
381
382    for (nstart = start ; ; ) {
383        unsigned long newflags;
384
385        /* Here we know that vma->vm_start <= nstart < vma->vm_end. */
386
387        newflags = vm_flags;
388        newflags |= (vma->vm_flags & ~(VM_READ | VM_WRITE | VM_EXEC));
389
390        /* newflags >> 4 shift VM_MAY% in place of VM_% */
391        if ((newflags & ~(newflags >> 4)) & (VM_READ | VM_WRITE | VM_EXEC)) {
392            error = -EACCES;
393            goto out;
394        }
395
396        error = security_file_mprotect(vma, reqprot, prot);
397        if (error)
398            goto out;
399
400        tmp = vma->vm_end;
401        if (tmp > end)
402            tmp = end;
403        error = mprotect_fixup(vma, &prev, nstart, tmp, newflags);
404        if (error)
405            goto out;
406        nstart = tmp;
407
408        if (nstart < prev->vm_end)
409            nstart = prev->vm_end;
410        if (nstart >= end)
411            goto out;
412
413        vma = prev->vm_next;
414        if (!vma || vma->vm_start != nstart) {
415            error = -ENOMEM;
416            goto out;
417        }
418    }
419out:
420    up_write(&current->mm->mmap_sem);
421    return error;
422}
423

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